...

Source file src/golang.org/x/image/draw/gen.go

Documentation: golang.org/x/image/draw

     1  // Copyright 2015 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build ignore
     6  
     7  package main
     8  
     9  import (
    10  	"bytes"
    11  	"flag"
    12  	"fmt"
    13  	"go/format"
    14  	"log"
    15  	"os"
    16  	"strings"
    17  )
    18  
    19  var debug = flag.Bool("debug", false, "")
    20  
    21  func main() {
    22  	flag.Parse()
    23  
    24  	w := new(bytes.Buffer)
    25  	w.WriteString("// generated by \"go run gen.go\". DO NOT EDIT.\n\n" +
    26  		"package draw\n\nimport (\n" +
    27  		"\"image\"\n" +
    28  		"\"image/color\"\n" +
    29  		"\"math\"\n" +
    30  		"\n" +
    31  		"\"golang.org/x/image/math/f64\"\n" +
    32  		")\n")
    33  
    34  	gen(w, "nnInterpolator", codeNNScaleLeaf, codeNNTransformLeaf)
    35  	gen(w, "ablInterpolator", codeABLScaleLeaf, codeABLTransformLeaf)
    36  	genKernel(w)
    37  
    38  	if *debug {
    39  		os.Stdout.Write(w.Bytes())
    40  		return
    41  	}
    42  	out, err := format.Source(w.Bytes())
    43  	if err != nil {
    44  		log.Fatal(err)
    45  	}
    46  	if err := os.WriteFile("impl.go", out, 0660); err != nil {
    47  		log.Fatal(err)
    48  	}
    49  }
    50  
    51  var (
    52  	// dsTypes are the (dst image type, src image type) pairs to generate
    53  	// scale_DType_SType implementations for. The last element in the slice
    54  	// should be the fallback pair ("Image", "image.Image").
    55  	//
    56  	// TODO: add *image.CMYK src type after Go 1.5 is released.
    57  	// An *image.CMYK is also alwaysOpaque.
    58  	dsTypes = []struct{ dType, sType string }{
    59  		{"*image.RGBA", "*image.Gray"},
    60  		{"*image.RGBA", "*image.NRGBA"},
    61  		{"*image.RGBA", "*image.RGBA"},
    62  		{"*image.RGBA", "*image.YCbCr"},
    63  		{"*image.RGBA", "image.RGBA64Image"},
    64  		{"*image.RGBA", "image.Image"},
    65  		{"RGBA64Image", "image.RGBA64Image"},
    66  		{"Image", "image.Image"},
    67  	}
    68  	dTypes, sTypes  []string
    69  	sTypesForDType  = map[string][]string{}
    70  	subsampleRatios = []string{
    71  		"444",
    72  		"422",
    73  		"420",
    74  		"440",
    75  	}
    76  	ops = []string{"Over", "Src"}
    77  	// alwaysOpaque are those image.Image implementations that are always
    78  	// opaque. For these types, Over is equivalent to the faster Src, in the
    79  	// absence of a source mask.
    80  	alwaysOpaque = map[string]bool{
    81  		"*image.Gray":  true,
    82  		"*image.YCbCr": true,
    83  	}
    84  )
    85  
    86  func init() {
    87  	dTypesSeen := map[string]bool{}
    88  	sTypesSeen := map[string]bool{}
    89  	for _, t := range dsTypes {
    90  		if !sTypesSeen[t.sType] {
    91  			sTypesSeen[t.sType] = true
    92  			sTypes = append(sTypes, t.sType)
    93  		}
    94  		if !dTypesSeen[t.dType] {
    95  			dTypesSeen[t.dType] = true
    96  			dTypes = append(dTypes, t.dType)
    97  		}
    98  		sTypesForDType[t.dType] = append(sTypesForDType[t.dType], t.sType)
    99  	}
   100  	sTypesForDType["anyDType"] = sTypes
   101  }
   102  
   103  type data struct {
   104  	dType    string
   105  	sType    string
   106  	sratio   string
   107  	receiver string
   108  	op       string
   109  }
   110  
   111  func gen(w *bytes.Buffer, receiver string, codes ...string) {
   112  	expn(w, codeRoot, &data{receiver: receiver})
   113  	for _, code := range codes {
   114  		for _, t := range dsTypes {
   115  			for _, op := range ops {
   116  				if op == "Over" && alwaysOpaque[t.sType] {
   117  					continue
   118  				}
   119  				expn(w, code, &data{
   120  					dType:    t.dType,
   121  					sType:    t.sType,
   122  					receiver: receiver,
   123  					op:       op,
   124  				})
   125  			}
   126  		}
   127  	}
   128  }
   129  
   130  func genKernel(w *bytes.Buffer) {
   131  	expn(w, codeKernelRoot, &data{})
   132  	for _, sType := range sTypes {
   133  		expn(w, codeKernelScaleLeafX, &data{
   134  			sType: sType,
   135  		})
   136  	}
   137  	for _, dType := range dTypes {
   138  		for _, op := range ops {
   139  			expn(w, codeKernelScaleLeafY, &data{
   140  				dType: dType,
   141  				op:    op,
   142  			})
   143  		}
   144  	}
   145  	for _, t := range dsTypes {
   146  		for _, op := range ops {
   147  			if op == "Over" && alwaysOpaque[t.sType] {
   148  				continue
   149  			}
   150  			expn(w, codeKernelTransformLeaf, &data{
   151  				dType: t.dType,
   152  				sType: t.sType,
   153  				op:    op,
   154  			})
   155  		}
   156  	}
   157  }
   158  
   159  func expn(w *bytes.Buffer, code string, d *data) {
   160  	if d.sType == "*image.YCbCr" && d.sratio == "" {
   161  		for _, sratio := range subsampleRatios {
   162  			e := *d
   163  			e.sratio = sratio
   164  			expn(w, code, &e)
   165  		}
   166  		return
   167  	}
   168  
   169  	for _, line := range strings.Split(code, "\n") {
   170  		line = expnLine(line, d)
   171  		if line == ";" {
   172  			continue
   173  		}
   174  		fmt.Fprintln(w, line)
   175  	}
   176  }
   177  
   178  func expnLine(line string, d *data) string {
   179  	for {
   180  		i := strings.IndexByte(line, '$')
   181  		if i < 0 {
   182  			break
   183  		}
   184  		prefix, s := line[:i], line[i+1:]
   185  
   186  		i = len(s)
   187  		for j, c := range s {
   188  			if !('A' <= c && c <= 'Z' || 'a' <= c && c <= 'z') {
   189  				i = j
   190  				break
   191  			}
   192  		}
   193  		dollar, suffix := s[:i], s[i:]
   194  
   195  		e := expnDollar(prefix, dollar, suffix, d)
   196  		if e == "" {
   197  			log.Fatalf("couldn't expand %q", line)
   198  		}
   199  		line = e
   200  	}
   201  	return line
   202  }
   203  
   204  // expnDollar expands a "$foo" fragment in a line of generated code. It returns
   205  // the empty string if there was a problem. It returns ";" if the generated
   206  // code is a no-op.
   207  func expnDollar(prefix, dollar, suffix string, d *data) string {
   208  	switch dollar {
   209  	case "dType":
   210  		return prefix + d.dType + suffix
   211  	case "dTypeRN":
   212  		return prefix + relName(d.dType) + suffix
   213  	case "sratio":
   214  		return prefix + d.sratio + suffix
   215  	case "sType":
   216  		return prefix + d.sType + suffix
   217  	case "sTypeRN":
   218  		return prefix + relName(d.sType) + suffix
   219  	case "receiver":
   220  		return prefix + d.receiver + suffix
   221  	case "op":
   222  		return prefix + d.op + suffix
   223  
   224  	case "switch":
   225  		return expnSwitch("", "", true, suffix)
   226  	case "switchD":
   227  		return expnSwitch("", "", false, suffix)
   228  	case "switchS":
   229  		return expnSwitch("", "anyDType", false, suffix)
   230  
   231  	case "preOuter":
   232  		switch d.dType {
   233  		default:
   234  			return ";"
   235  		case "Image":
   236  			s := ""
   237  			if d.sType == "image.Image" || d.sType == "image.RGBA64Image" {
   238  				s = "srcMask, smp := opts.SrcMask, opts.SrcMaskP\n"
   239  			}
   240  			return s +
   241  				"dstMask, dmp := opts.DstMask, opts.DstMaskP\n" +
   242  				"dstColorRGBA64 := &color.RGBA64{}\n" +
   243  				"dstColor := color.Color(dstColorRGBA64)"
   244  		case "RGBA64Image":
   245  			s := ""
   246  			if d.sType == "image.Image" || d.sType == "image.RGBA64Image" {
   247  				s = "srcMask, smp := opts.SrcMask, opts.SrcMaskP\n"
   248  			}
   249  			return s +
   250  				"dstMask, dmp := opts.DstMask, opts.DstMaskP\n" +
   251  				"dstColorRGBA64 := color.RGBA64{}\n"
   252  		}
   253  
   254  	case "preInner":
   255  		switch d.dType {
   256  		default:
   257  			return ";"
   258  		case "*image.RGBA":
   259  			return "d := " + pixOffset("dst", "dr.Min.X+adr.Min.X", "dr.Min.Y+int(dy)", "*4", "*dst.Stride")
   260  		}
   261  
   262  	case "preKernelOuter":
   263  		switch d.sType {
   264  		default:
   265  			return ";"
   266  		case "image.Image", "image.RGBA64Image":
   267  			return "srcMask, smp := opts.SrcMask, opts.SrcMaskP"
   268  		}
   269  
   270  	case "preKernelInner":
   271  		switch d.dType {
   272  		default:
   273  			return ";"
   274  		case "*image.RGBA":
   275  			return "d := " + pixOffset("dst", "dr.Min.X+int(dx)", "dr.Min.Y+adr.Min.Y", "*4", "*dst.Stride")
   276  		}
   277  
   278  	case "blend":
   279  		args, _ := splitArgs(suffix)
   280  		if len(args) != 4 {
   281  			return ""
   282  		}
   283  		switch d.sType {
   284  		default:
   285  			return argf(args, ""+
   286  				"$3r = $0*$1r + $2*$3r\n"+
   287  				"$3g = $0*$1g + $2*$3g\n"+
   288  				"$3b = $0*$1b + $2*$3b\n"+
   289  				"$3a = $0*$1a + $2*$3a",
   290  			)
   291  		case "*image.Gray":
   292  			return argf(args, ""+
   293  				"$3r = $0*$1r + $2*$3r",
   294  			)
   295  		case "*image.YCbCr":
   296  			return argf(args, ""+
   297  				"$3r = $0*$1r + $2*$3r\n"+
   298  				"$3g = $0*$1g + $2*$3g\n"+
   299  				"$3b = $0*$1b + $2*$3b",
   300  			)
   301  		}
   302  
   303  	case "clampToAlpha":
   304  		if alwaysOpaque[d.sType] {
   305  			return ";"
   306  		}
   307  		// Go uses alpha-premultiplied color. The naive computation can lead to
   308  		// invalid colors, e.g. red > alpha, when some weights are negative.
   309  		return `
   310  			if pr > pa {
   311  				pr = pa
   312  			}
   313  			if pg > pa {
   314  				pg = pa
   315  			}
   316  			if pb > pa {
   317  				pb = pa
   318  			}
   319  		`
   320  
   321  	case "convFtou":
   322  		args, _ := splitArgs(suffix)
   323  		if len(args) != 2 {
   324  			return ""
   325  		}
   326  
   327  		switch d.sType {
   328  		default:
   329  			return argf(args, ""+
   330  				"$0r := uint32($1r)\n"+
   331  				"$0g := uint32($1g)\n"+
   332  				"$0b := uint32($1b)\n"+
   333  				"$0a := uint32($1a)",
   334  			)
   335  		case "*image.Gray":
   336  			return argf(args, ""+
   337  				"$0r := uint32($1r)",
   338  			)
   339  		case "*image.YCbCr":
   340  			return argf(args, ""+
   341  				"$0r := uint32($1r)\n"+
   342  				"$0g := uint32($1g)\n"+
   343  				"$0b := uint32($1b)",
   344  			)
   345  		case "image.RGBA64Image":
   346  			return argf(args, ""+
   347  				"$0 := color.RGBA64{uint16($1r), uint16($1g), uint16($1b), uint16($1a)}",
   348  			)
   349  		}
   350  
   351  	case "outputu":
   352  		args, _ := splitArgs(suffix)
   353  		if len(args) != 3 {
   354  			return ""
   355  		}
   356  
   357  		switch d.op {
   358  		case "Over":
   359  			switch d.dType {
   360  			default:
   361  				log.Fatalf("bad dType %q", d.dType)
   362  			case "Image":
   363  				return argf(args, ""+
   364  					"qr, qg, qb, qa := dst.At($0, $1).RGBA()\n"+
   365  					"if dstMask != nil {\n"+
   366  					"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   367  					"	$2r = $2r * ma / 0xffff\n"+
   368  					"	$2g = $2g * ma / 0xffff\n"+
   369  					"	$2b = $2b * ma / 0xffff\n"+
   370  					"	$2a = $2a * ma / 0xffff\n"+
   371  					"}\n"+
   372  					"$2a1 := 0xffff - $2a\n"+
   373  					"dstColorRGBA64.R = uint16(qr*$2a1/0xffff + $2r)\n"+
   374  					"dstColorRGBA64.G = uint16(qg*$2a1/0xffff + $2g)\n"+
   375  					"dstColorRGBA64.B = uint16(qb*$2a1/0xffff + $2b)\n"+
   376  					"dstColorRGBA64.A = uint16(qa*$2a1/0xffff + $2a)\n"+
   377  					"dst.Set($0, $1, dstColor)",
   378  				)
   379  			case "RGBA64Image":
   380  				switch d.sType {
   381  				default:
   382  					return argf(args, ""+
   383  						"q := dst.RGBA64At($0, $1)\n"+
   384  						"if dstMask != nil {\n"+
   385  						"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   386  						"	$2r = $2r * ma / 0xffff\n"+
   387  						"	$2g = $2g * ma / 0xffff\n"+
   388  						"	$2b = $2b * ma / 0xffff\n"+
   389  						"	$2a = $2a * ma / 0xffff\n"+
   390  						"}\n"+
   391  						"$2a1 := 0xffff - $2a\n"+
   392  						"dstColorRGBA64.R = uint16(uint32(q.R)*$2a1/0xffff + $2r)\n"+
   393  						"dstColorRGBA64.G = uint16(uint32(q.G)*$2a1/0xffff + $2g)\n"+
   394  						"dstColorRGBA64.B = uint16(uint32(q.B)*$2a1/0xffff + $2b)\n"+
   395  						"dstColorRGBA64.A = uint16(uint32(q.A)*$2a1/0xffff + $2a)\n"+
   396  						"dst.Set($0, $1, dstColorRGBA64)",
   397  					)
   398  				case "image.RGBA64Image":
   399  					return argf(args, ""+
   400  						"q := dst.RGBA64At($0, $1)\n"+
   401  						"if dstMask != nil {\n"+
   402  						"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   403  						"	$2.R = uint16(uint32($2.R) * ma / 0xffff)\n"+
   404  						"	$2.G = uint16(uint32($2.G) * ma / 0xffff)\n"+
   405  						"	$2.B = uint16(uint32($2.B) * ma / 0xffff)\n"+
   406  						"	$2.A = uint16(uint32($2.A) * ma / 0xffff)\n"+
   407  						"}\n"+
   408  						"$2a1 := 0xffff - uint32($2.A)\n"+
   409  						"dstColorRGBA64.R = uint16(uint32(q.R)*$2a1/0xffff + uint32($2.R))\n"+
   410  						"dstColorRGBA64.G = uint16(uint32(q.G)*$2a1/0xffff + uint32($2.G))\n"+
   411  						"dstColorRGBA64.B = uint16(uint32(q.B)*$2a1/0xffff + uint32($2.B))\n"+
   412  						"dstColorRGBA64.A = uint16(uint32(q.A)*$2a1/0xffff + uint32($2.A))\n"+
   413  						"dst.Set($0, $1, dstColorRGBA64)",
   414  					)
   415  				}
   416  			case "*image.RGBA":
   417  				switch d.sType {
   418  				default:
   419  					return argf(args, ""+
   420  						"$2a1 := (0xffff - $2a) * 0x101\n"+
   421  						"dst.Pix[d+0] = uint8((uint32(dst.Pix[d+0])*$2a1/0xffff + $2r) >> 8)\n"+
   422  						"dst.Pix[d+1] = uint8((uint32(dst.Pix[d+1])*$2a1/0xffff + $2g) >> 8)\n"+
   423  						"dst.Pix[d+2] = uint8((uint32(dst.Pix[d+2])*$2a1/0xffff + $2b) >> 8)\n"+
   424  						"dst.Pix[d+3] = uint8((uint32(dst.Pix[d+3])*$2a1/0xffff + $2a) >> 8)",
   425  					)
   426  				case "image.RGBA64Image":
   427  					return argf(args, ""+
   428  						"$2a1 := (0xffff - uint32($2.A)) * 0x101\n"+
   429  						"dst.Pix[d+0] = uint8((uint32(dst.Pix[d+0])*$2a1/0xffff + uint32($2.R)) >> 8)\n"+
   430  						"dst.Pix[d+1] = uint8((uint32(dst.Pix[d+1])*$2a1/0xffff + uint32($2.G)) >> 8)\n"+
   431  						"dst.Pix[d+2] = uint8((uint32(dst.Pix[d+2])*$2a1/0xffff + uint32($2.B)) >> 8)\n"+
   432  						"dst.Pix[d+3] = uint8((uint32(dst.Pix[d+3])*$2a1/0xffff + uint32($2.A)) >> 8)",
   433  					)
   434  				}
   435  			}
   436  
   437  		case "Src":
   438  			switch d.dType {
   439  			default:
   440  				log.Fatalf("bad dType %q", d.dType)
   441  			case "Image":
   442  				return argf(args, ""+
   443  					"if dstMask != nil {\n"+
   444  					"	qr, qg, qb, qa := dst.At($0, $1).RGBA()\n"+
   445  					"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   446  					"	pr = pr * ma / 0xffff\n"+
   447  					"	pg = pg * ma / 0xffff\n"+
   448  					"	pb = pb * ma / 0xffff\n"+
   449  					"	pa = pa * ma / 0xffff\n"+
   450  					"	$2a1 := 0xffff - ma\n"+ // Note that this is ma, not $2a.
   451  					"	dstColorRGBA64.R = uint16(qr*$2a1/0xffff + $2r)\n"+
   452  					"	dstColorRGBA64.G = uint16(qg*$2a1/0xffff + $2g)\n"+
   453  					"	dstColorRGBA64.B = uint16(qb*$2a1/0xffff + $2b)\n"+
   454  					"	dstColorRGBA64.A = uint16(qa*$2a1/0xffff + $2a)\n"+
   455  					"	dst.Set($0, $1, dstColor)\n"+
   456  					"} else {\n"+
   457  					"	dstColorRGBA64.R = uint16($2r)\n"+
   458  					"	dstColorRGBA64.G = uint16($2g)\n"+
   459  					"	dstColorRGBA64.B = uint16($2b)\n"+
   460  					"	dstColorRGBA64.A = uint16($2a)\n"+
   461  					"	dst.Set($0, $1, dstColor)\n"+
   462  					"}",
   463  				)
   464  			case "RGBA64Image":
   465  				switch d.sType {
   466  				default:
   467  					return argf(args, ""+
   468  						"if dstMask != nil {\n"+
   469  						"	q := dst.RGBA64At($0, $1)\n"+
   470  						"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   471  						"	pr = pr * ma / 0xffff\n"+
   472  						"	pg = pg * ma / 0xffff\n"+
   473  						"	pb = pb * ma / 0xffff\n"+
   474  						"	pa = pa * ma / 0xffff\n"+
   475  						"	$2a1 := 0xffff - ma\n"+ // Note that this is ma, not $2a.
   476  						"	dstColorRGBA64.R = uint16(uint32(q.R)*$2a1/0xffff + $2r)\n"+
   477  						"	dstColorRGBA64.G = uint16(uint32(q.G)*$2a1/0xffff + $2g)\n"+
   478  						"	dstColorRGBA64.B = uint16(uint32(q.B)*$2a1/0xffff + $2b)\n"+
   479  						"	dstColorRGBA64.A = uint16(uint32(q.A)*$2a1/0xffff + $2a)\n"+
   480  						"	dst.Set($0, $1, dstColorRGBA64)\n"+
   481  						"} else {\n"+
   482  						"	dstColorRGBA64.R = uint16($2r)\n"+
   483  						"	dstColorRGBA64.G = uint16($2g)\n"+
   484  						"	dstColorRGBA64.B = uint16($2b)\n"+
   485  						"	dstColorRGBA64.A = uint16($2a)\n"+
   486  						"	dst.Set($0, $1, dstColorRGBA64)\n"+
   487  						"}",
   488  					)
   489  				case "image.RGBA64Image":
   490  					return argf(args, ""+
   491  						"if dstMask != nil {\n"+
   492  						"	q := dst.RGBA64At($0, $1)\n"+
   493  						"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   494  						"	p.R = uint16(uint32(p.R) * ma / 0xffff)\n"+
   495  						"	p.G = uint16(uint32(p.G) * ma / 0xffff)\n"+
   496  						"	p.B = uint16(uint32(p.B) * ma / 0xffff)\n"+
   497  						"	p.A = uint16(uint32(p.A) * ma / 0xffff)\n"+
   498  						"	$2a1 := 0xffff - ma\n"+ // Note that this is ma, not $2a.
   499  						"	dstColorRGBA64.R = uint16(uint32(q.R)*$2a1/0xffff + uint32($2.R))\n"+
   500  						"	dstColorRGBA64.G = uint16(uint32(q.G)*$2a1/0xffff + uint32($2.G))\n"+
   501  						"	dstColorRGBA64.B = uint16(uint32(q.B)*$2a1/0xffff + uint32($2.B))\n"+
   502  						"	dstColorRGBA64.A = uint16(uint32(q.A)*$2a1/0xffff + uint32($2.A))\n"+
   503  						"	dst.Set($0, $1, dstColorRGBA64)\n"+
   504  						"} else {\n"+
   505  						"	dst.Set($0, $1, $2)\n"+
   506  						"}",
   507  					)
   508  				}
   509  			case "*image.RGBA":
   510  				switch d.sType {
   511  				default:
   512  					return argf(args, ""+
   513  						"dst.Pix[d+0] = uint8($2r >> 8)\n"+
   514  						"dst.Pix[d+1] = uint8($2g >> 8)\n"+
   515  						"dst.Pix[d+2] = uint8($2b >> 8)\n"+
   516  						"dst.Pix[d+3] = uint8($2a >> 8)",
   517  					)
   518  				case "*image.Gray":
   519  					return argf(args, ""+
   520  						"out := uint8($2r >> 8)\n"+
   521  						"dst.Pix[d+0] = out\n"+
   522  						"dst.Pix[d+1] = out\n"+
   523  						"dst.Pix[d+2] = out\n"+
   524  						"dst.Pix[d+3] = 0xff",
   525  					)
   526  				case "*image.YCbCr":
   527  					return argf(args, ""+
   528  						"dst.Pix[d+0] = uint8($2r >> 8)\n"+
   529  						"dst.Pix[d+1] = uint8($2g >> 8)\n"+
   530  						"dst.Pix[d+2] = uint8($2b >> 8)\n"+
   531  						"dst.Pix[d+3] = 0xff",
   532  					)
   533  				case "image.RGBA64Image":
   534  					return argf(args, ""+
   535  						"dst.Pix[d+0] = uint8($2.R >> 8)\n"+
   536  						"dst.Pix[d+1] = uint8($2.G >> 8)\n"+
   537  						"dst.Pix[d+2] = uint8($2.B >> 8)\n"+
   538  						"dst.Pix[d+3] = uint8($2.A >> 8)",
   539  					)
   540  				}
   541  			}
   542  		}
   543  
   544  	case "outputf":
   545  		args, _ := splitArgs(suffix)
   546  		if len(args) != 5 {
   547  			return ""
   548  		}
   549  		ret := ""
   550  
   551  		switch d.op {
   552  		case "Over":
   553  			switch d.dType {
   554  			default:
   555  				log.Fatalf("bad dType %q", d.dType)
   556  			case "Image":
   557  				ret = argf(args, ""+
   558  					"qr, qg, qb, qa := dst.At($0, $1).RGBA()\n"+
   559  					"$3r0 := uint32($2($3r * $4))\n"+
   560  					"$3g0 := uint32($2($3g * $4))\n"+
   561  					"$3b0 := uint32($2($3b * $4))\n"+
   562  					"$3a0 := uint32($2($3a * $4))\n"+
   563  					"if dstMask != nil {\n"+
   564  					"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   565  					"	$3r0 = $3r0 * ma / 0xffff\n"+
   566  					"	$3g0 = $3g0 * ma / 0xffff\n"+
   567  					"	$3b0 = $3b0 * ma / 0xffff\n"+
   568  					"	$3a0 = $3a0 * ma / 0xffff\n"+
   569  					"}\n"+
   570  					"$3a1 := 0xffff - $3a0\n"+
   571  					"dstColorRGBA64.R = uint16(qr*$3a1/0xffff + $3r0)\n"+
   572  					"dstColorRGBA64.G = uint16(qg*$3a1/0xffff + $3g0)\n"+
   573  					"dstColorRGBA64.B = uint16(qb*$3a1/0xffff + $3b0)\n"+
   574  					"dstColorRGBA64.A = uint16(qa*$3a1/0xffff + $3a0)\n"+
   575  					"dst.Set($0, $1, dstColor)",
   576  				)
   577  			case "RGBA64Image":
   578  				ret = argf(args, ""+
   579  					"q := dst.RGBA64At($0, $1)\n"+
   580  					"$3r0 := uint32($2($3r * $4))\n"+
   581  					"$3g0 := uint32($2($3g * $4))\n"+
   582  					"$3b0 := uint32($2($3b * $4))\n"+
   583  					"$3a0 := uint32($2($3a * $4))\n"+
   584  					"if dstMask != nil {\n"+
   585  					"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   586  					"	$3r0 = $3r0 * ma / 0xffff\n"+
   587  					"	$3g0 = $3g0 * ma / 0xffff\n"+
   588  					"	$3b0 = $3b0 * ma / 0xffff\n"+
   589  					"	$3a0 = $3a0 * ma / 0xffff\n"+
   590  					"}\n"+
   591  					"$3a1 := 0xffff - $3a0\n"+
   592  					"dstColorRGBA64.R = uint16(uint32(q.R)*$3a1/0xffff + $3r0)\n"+
   593  					"dstColorRGBA64.G = uint16(uint32(q.G)*$3a1/0xffff + $3g0)\n"+
   594  					"dstColorRGBA64.B = uint16(uint32(q.B)*$3a1/0xffff + $3b0)\n"+
   595  					"dstColorRGBA64.A = uint16(uint32(q.A)*$3a1/0xffff + $3a0)\n"+
   596  					"dst.SetRGBA64($0, $1, dstColorRGBA64)",
   597  				)
   598  			case "*image.RGBA":
   599  				ret = argf(args, ""+
   600  					"$3r0 := uint32($2($3r * $4))\n"+
   601  					"$3g0 := uint32($2($3g * $4))\n"+
   602  					"$3b0 := uint32($2($3b * $4))\n"+
   603  					"$3a0 := uint32($2($3a * $4))\n"+
   604  					"$3a1 := (0xffff - uint32($3a0)) * 0x101\n"+
   605  					"dst.Pix[d+0] = uint8((uint32(dst.Pix[d+0])*$3a1/0xffff + $3r0) >> 8)\n"+
   606  					"dst.Pix[d+1] = uint8((uint32(dst.Pix[d+1])*$3a1/0xffff + $3g0) >> 8)\n"+
   607  					"dst.Pix[d+2] = uint8((uint32(dst.Pix[d+2])*$3a1/0xffff + $3b0) >> 8)\n"+
   608  					"dst.Pix[d+3] = uint8((uint32(dst.Pix[d+3])*$3a1/0xffff + $3a0) >> 8)",
   609  				)
   610  			}
   611  
   612  		case "Src":
   613  			switch d.dType {
   614  			default:
   615  				log.Fatalf("bad dType %q", d.dType)
   616  			case "Image":
   617  				ret = argf(args, ""+
   618  					"if dstMask != nil {\n"+
   619  					"	qr, qg, qb, qa := dst.At($0, $1).RGBA()\n"+
   620  					"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   621  					"	pr := uint32($2($3r * $4)) * ma / 0xffff\n"+
   622  					"	pg := uint32($2($3g * $4)) * ma / 0xffff\n"+
   623  					"	pb := uint32($2($3b * $4)) * ma / 0xffff\n"+
   624  					"	pa := uint32($2($3a * $4)) * ma / 0xffff\n"+
   625  					"	pa1 := 0xffff - ma\n"+ // Note that this is ma, not pa.
   626  					"	dstColorRGBA64.R = uint16(qr*pa1/0xffff + pr)\n"+
   627  					"	dstColorRGBA64.G = uint16(qg*pa1/0xffff + pg)\n"+
   628  					"	dstColorRGBA64.B = uint16(qb*pa1/0xffff + pb)\n"+
   629  					"	dstColorRGBA64.A = uint16(qa*pa1/0xffff + pa)\n"+
   630  					"	dst.Set($0, $1, dstColor)\n"+
   631  					"} else {\n"+
   632  					"	dstColorRGBA64.R = $2($3r * $4)\n"+
   633  					"	dstColorRGBA64.G = $2($3g * $4)\n"+
   634  					"	dstColorRGBA64.B = $2($3b * $4)\n"+
   635  					"	dstColorRGBA64.A = $2($3a * $4)\n"+
   636  					"	dst.Set($0, $1, dstColor)\n"+
   637  					"}",
   638  				)
   639  			case "RGBA64Image":
   640  				ret = argf(args, ""+
   641  					"if dstMask != nil {\n"+
   642  					"	q := dst.RGBA64At($0, $1)\n"+
   643  					"	_, _, _, ma := dstMask.At(dmp.X + $0, dmp.Y + $1).RGBA()\n"+
   644  					"	pr := uint32($2($3r * $4)) * ma / 0xffff\n"+
   645  					"	pg := uint32($2($3g * $4)) * ma / 0xffff\n"+
   646  					"	pb := uint32($2($3b * $4)) * ma / 0xffff\n"+
   647  					"	pa := uint32($2($3a * $4)) * ma / 0xffff\n"+
   648  					"	pa1 := 0xffff - ma\n"+ // Note that this is ma, not pa.
   649  					"	dstColorRGBA64.R = uint16(uint32(q.R)*pa1/0xffff + pr)\n"+
   650  					"	dstColorRGBA64.G = uint16(uint32(q.G)*pa1/0xffff + pg)\n"+
   651  					"	dstColorRGBA64.B = uint16(uint32(q.B)*pa1/0xffff + pb)\n"+
   652  					"	dstColorRGBA64.A = uint16(uint32(q.A)*pa1/0xffff + pa)\n"+
   653  					"	dst.SetRGBA64($0, $1, dstColorRGBA64)\n"+
   654  					"} else {\n"+
   655  					"	dstColorRGBA64.R = $2($3r * $4)\n"+
   656  					"	dstColorRGBA64.G = $2($3g * $4)\n"+
   657  					"	dstColorRGBA64.B = $2($3b * $4)\n"+
   658  					"	dstColorRGBA64.A = $2($3a * $4)\n"+
   659  					"	dst.SetRGBA64($0, $1, dstColorRGBA64)\n"+
   660  					"}",
   661  				)
   662  			case "*image.RGBA":
   663  				switch d.sType {
   664  				default:
   665  					ret = argf(args, ""+
   666  						"dst.Pix[d+0] = uint8($2($3r * $4) >> 8)\n"+
   667  						"dst.Pix[d+1] = uint8($2($3g * $4) >> 8)\n"+
   668  						"dst.Pix[d+2] = uint8($2($3b * $4) >> 8)\n"+
   669  						"dst.Pix[d+3] = uint8($2($3a * $4) >> 8)",
   670  					)
   671  				case "*image.Gray":
   672  					ret = argf(args, ""+
   673  						"out := uint8($2($3r * $4) >> 8)\n"+
   674  						"dst.Pix[d+0] = out\n"+
   675  						"dst.Pix[d+1] = out\n"+
   676  						"dst.Pix[d+2] = out\n"+
   677  						"dst.Pix[d+3] = 0xff",
   678  					)
   679  				case "*image.YCbCr":
   680  					ret = argf(args, ""+
   681  						"dst.Pix[d+0] = uint8($2($3r * $4) >> 8)\n"+
   682  						"dst.Pix[d+1] = uint8($2($3g * $4) >> 8)\n"+
   683  						"dst.Pix[d+2] = uint8($2($3b * $4) >> 8)\n"+
   684  						"dst.Pix[d+3] = 0xff",
   685  					)
   686  				}
   687  			}
   688  		}
   689  
   690  		return strings.Replace(ret, " * 1)", ")", -1)
   691  
   692  	case "srcf", "srcu":
   693  		lhs, eqOp := splitEq(prefix)
   694  		if lhs == "" {
   695  			return ""
   696  		}
   697  		args, extra := splitArgs(suffix)
   698  		if len(args) != 2 {
   699  			return ""
   700  		}
   701  
   702  		tmp := ""
   703  		if dollar == "srcf" {
   704  			tmp = "u"
   705  		}
   706  
   707  		// TODO: there's no need to multiply by 0x101 in the switch below if
   708  		// the next thing we're going to do is shift right by 8.
   709  
   710  		buf := new(bytes.Buffer)
   711  		switch d.sType {
   712  		default:
   713  			log.Fatalf("bad sType %q", d.sType)
   714  		case "image.Image":
   715  			fmt.Fprintf(buf, ""+
   716  				"%sr%s, %sg%s, %sb%s, %sa%s := src.At(%s, %s).RGBA()\n",
   717  				lhs, tmp, lhs, tmp, lhs, tmp, lhs, tmp, args[0], args[1],
   718  			)
   719  			if d.dType == "" || d.dType == "Image" || d.dType == "RGBA64Image" {
   720  				fmt.Fprintf(buf, ""+
   721  					"if srcMask != nil {\n"+
   722  					"	_, _, _, ma := srcMask.At(smp.X+%[1]s, smp.Y+%[2]s).RGBA()\n"+
   723  					"	%[3]sr%[4]s = %[3]sr%[4]s * ma / 0xffff\n"+
   724  					"	%[3]sg%[4]s = %[3]sg%[4]s * ma / 0xffff\n"+
   725  					"	%[3]sb%[4]s = %[3]sb%[4]s * ma / 0xffff\n"+
   726  					"	%[3]sa%[4]s = %[3]sa%[4]s * ma / 0xffff\n"+
   727  					"}\n",
   728  					args[0], args[1],
   729  					lhs, tmp,
   730  				)
   731  			}
   732  		case "image.RGBA64Image":
   733  			fmt.Fprintf(buf, ""+
   734  				"%s%s := src.RGBA64At(%s, %s)\n",
   735  				lhs, tmp, args[0], args[1],
   736  			)
   737  			if d.dType == "" || d.dType == "Image" || d.dType == "RGBA64Image" {
   738  				fmt.Fprintf(buf, ""+
   739  					"if srcMask != nil {\n"+
   740  					"	_, _, _, ma := srcMask.At(smp.X+%[1]s, smp.Y+%[2]s).RGBA()\n"+
   741  					"	%[3]s%[4]s.R = uint16(uint32(%[3]s%[4]s.R) * ma / 0xffff)\n"+
   742  					"	%[3]s%[4]s.G = uint16(uint32(%[3]s%[4]s.G) * ma / 0xffff)\n"+
   743  					"	%[3]s%[4]s.B = uint16(uint32(%[3]s%[4]s.B) * ma / 0xffff)\n"+
   744  					"	%[3]s%[4]s.A = uint16(uint32(%[3]s%[4]s.A) * ma / 0xffff)\n"+
   745  					"}\n",
   746  					args[0], args[1],
   747  					lhs, tmp,
   748  				)
   749  			}
   750  		case "*image.Gray":
   751  			fmt.Fprintf(buf, ""+
   752  				"%[1]si := %[3]s\n"+
   753  				"%[1]sr%[2]s := uint32(src.Pix[%[1]si]) * 0x101\n",
   754  				lhs, tmp, pixOffset("src", args[0], args[1], "", "*src.Stride"),
   755  			)
   756  		case "*image.NRGBA":
   757  			fmt.Fprintf(buf, ""+
   758  				"%[1]si := %[3]s\n"+
   759  				"%[1]sa%[2]s := uint32(src.Pix[%[1]si+3]) * 0x101\n"+
   760  				"%[1]sr%[2]s := uint32(src.Pix[%[1]si+0]) * %[1]sa%s / 0xff\n"+
   761  				"%[1]sg%[2]s := uint32(src.Pix[%[1]si+1]) * %[1]sa%s / 0xff\n"+
   762  				"%[1]sb%[2]s := uint32(src.Pix[%[1]si+2]) * %[1]sa%s / 0xff\n",
   763  				lhs, tmp, pixOffset("src", args[0], args[1], "*4", "*src.Stride"),
   764  			)
   765  		case "*image.RGBA":
   766  			fmt.Fprintf(buf, ""+
   767  				"%[1]si := %[3]s\n"+
   768  				"%[1]sr%[2]s := uint32(src.Pix[%[1]si+0]) * 0x101\n"+
   769  				"%[1]sg%[2]s := uint32(src.Pix[%[1]si+1]) * 0x101\n"+
   770  				"%[1]sb%[2]s := uint32(src.Pix[%[1]si+2]) * 0x101\n"+
   771  				"%[1]sa%[2]s := uint32(src.Pix[%[1]si+3]) * 0x101\n",
   772  				lhs, tmp, pixOffset("src", args[0], args[1], "*4", "*src.Stride"),
   773  			)
   774  		case "*image.YCbCr":
   775  			fmt.Fprintf(buf, ""+
   776  				"%[1]si := %[2]s\n"+
   777  				"%[1]sj := %[3]s\n"+
   778  				"%[4]s\n",
   779  				lhs, pixOffset("src", args[0], args[1], "", "*src.YStride"),
   780  				cOffset(args[0], args[1], d.sratio),
   781  				ycbcrToRGB(lhs, tmp),
   782  			)
   783  		}
   784  
   785  		if dollar == "srcf" {
   786  			switch d.sType {
   787  			default:
   788  				fmt.Fprintf(buf, ""+
   789  					"%[1]sr %[2]s float64(%[1]sru)%[3]s\n"+
   790  					"%[1]sg %[2]s float64(%[1]sgu)%[3]s\n"+
   791  					"%[1]sb %[2]s float64(%[1]sbu)%[3]s\n"+
   792  					"%[1]sa %[2]s float64(%[1]sau)%[3]s\n",
   793  					lhs, eqOp, extra,
   794  				)
   795  			case "*image.Gray":
   796  				fmt.Fprintf(buf, ""+
   797  					"%[1]sr %[2]s float64(%[1]sru)%[3]s\n",
   798  					lhs, eqOp, extra,
   799  				)
   800  			case "*image.YCbCr":
   801  				fmt.Fprintf(buf, ""+
   802  					"%[1]sr %[2]s float64(%[1]sru)%[3]s\n"+
   803  					"%[1]sg %[2]s float64(%[1]sgu)%[3]s\n"+
   804  					"%[1]sb %[2]s float64(%[1]sbu)%[3]s\n",
   805  					lhs, eqOp, extra,
   806  				)
   807  			case "image.RGBA64Image":
   808  				fmt.Fprintf(buf, ""+
   809  					"%[1]sr %[2]s float64(%[1]su.R)%[3]s\n"+
   810  					"%[1]sg %[2]s float64(%[1]su.G)%[3]s\n"+
   811  					"%[1]sb %[2]s float64(%[1]su.B)%[3]s\n"+
   812  					"%[1]sa %[2]s float64(%[1]su.A)%[3]s\n",
   813  					lhs, eqOp, extra,
   814  				)
   815  			}
   816  		}
   817  
   818  		return strings.TrimSpace(buf.String())
   819  
   820  	case "tweakD":
   821  		if d.dType == "*image.RGBA" {
   822  			return "d += dst.Stride"
   823  		}
   824  		return ";"
   825  
   826  	case "tweakDx":
   827  		if d.dType == "*image.RGBA" {
   828  			return strings.Replace(prefix, "dx++", "dx, d = dx+1, d+4", 1)
   829  		}
   830  		return prefix
   831  
   832  	case "tweakDy":
   833  		if d.dType == "*image.RGBA" {
   834  			return strings.Replace(prefix, "for dy, s", "for _, s", 1)
   835  		}
   836  		return prefix
   837  
   838  	case "tweakP":
   839  		switch d.sType {
   840  		case "*image.Gray":
   841  			if strings.HasPrefix(strings.TrimSpace(prefix), "pa * ") {
   842  				return "1,"
   843  			}
   844  			return "pr,"
   845  		case "*image.YCbCr":
   846  			if strings.HasPrefix(strings.TrimSpace(prefix), "pa * ") {
   847  				return "1,"
   848  			}
   849  		}
   850  		return prefix
   851  
   852  	case "tweakPr":
   853  		if d.sType == "*image.Gray" {
   854  			return "pr *= s.invTotalWeightFFFF"
   855  		}
   856  		return ";"
   857  
   858  	case "tweakVarP":
   859  		switch d.sType {
   860  		case "*image.Gray":
   861  			return strings.Replace(prefix, "var pr, pg, pb, pa", "var pr", 1)
   862  		case "*image.YCbCr":
   863  			return strings.Replace(prefix, "var pr, pg, pb, pa", "var pr, pg, pb", 1)
   864  		}
   865  		return prefix
   866  	}
   867  	return ""
   868  }
   869  
   870  func expnSwitch(op, dType string, expandBoth bool, template string) string {
   871  	if op == "" && dType != "anyDType" {
   872  		lines := []string{"switch op {"}
   873  		for _, op = range ops {
   874  			lines = append(lines,
   875  				fmt.Sprintf("case %s:", op),
   876  				expnSwitch(op, dType, expandBoth, template),
   877  			)
   878  		}
   879  		lines = append(lines, "}")
   880  		return strings.Join(lines, "\n")
   881  	}
   882  
   883  	switchVar := "dst"
   884  	if dType != "" {
   885  		switchVar = "src"
   886  	}
   887  	lines := []string{fmt.Sprintf("switch %s := %s.(type) {", switchVar, switchVar)}
   888  
   889  	fallback, values := "Image", dTypes
   890  	if dType != "" {
   891  		fallback, values = "image.Image", sTypesForDType[dType]
   892  	}
   893  	for _, v := range values {
   894  		if dType != "" {
   895  			// v is the sType. Skip those always-opaque sTypes, where Over is
   896  			// equivalent to Src.
   897  			if op == "Over" && alwaysOpaque[v] {
   898  				continue
   899  			}
   900  		}
   901  
   902  		if v == fallback {
   903  			lines = append(lines, "default:")
   904  		} else {
   905  			lines = append(lines, fmt.Sprintf("case %s:", v))
   906  		}
   907  
   908  		if dType != "" {
   909  			if v == "*image.YCbCr" {
   910  				lines = append(lines, expnSwitchYCbCr(op, dType, template))
   911  			} else {
   912  				lines = append(lines, expnLine(template, &data{dType: dType, sType: v, op: op}))
   913  			}
   914  		} else if !expandBoth {
   915  			lines = append(lines, expnLine(template, &data{dType: v, op: op}))
   916  		} else {
   917  			lines = append(lines, expnSwitch(op, v, false, template))
   918  		}
   919  	}
   920  
   921  	lines = append(lines, "}")
   922  	return strings.Join(lines, "\n")
   923  }
   924  
   925  func expnSwitchYCbCr(op, dType, template string) string {
   926  	lines := []string{
   927  		"switch src.SubsampleRatio {",
   928  		"default:",
   929  		expnLine(template, &data{dType: dType, sType: "image.Image", op: op}),
   930  	}
   931  	for _, sratio := range subsampleRatios {
   932  		lines = append(lines,
   933  			fmt.Sprintf("case image.YCbCrSubsampleRatio%s:", sratio),
   934  			expnLine(template, &data{dType: dType, sType: "*image.YCbCr", sratio: sratio, op: op}),
   935  		)
   936  	}
   937  	lines = append(lines, "}")
   938  	return strings.Join(lines, "\n")
   939  }
   940  
   941  func argf(args []string, s string) string {
   942  	if len(args) > 9 {
   943  		panic("too many args")
   944  	}
   945  	for i, a := range args {
   946  		old := fmt.Sprintf("$%d", i)
   947  		s = strings.Replace(s, old, a, -1)
   948  	}
   949  	return s
   950  }
   951  
   952  func pixOffset(m, x, y, xstride, ystride string) string {
   953  	return fmt.Sprintf("(%s-%s.Rect.Min.Y)%s + (%s-%s.Rect.Min.X)%s", y, m, ystride, x, m, xstride)
   954  }
   955  
   956  func cOffset(x, y, sratio string) string {
   957  	switch sratio {
   958  	case "444":
   959  		return fmt.Sprintf("( %s    - src.Rect.Min.Y  )*src.CStride + ( %s    - src.Rect.Min.X  )", y, x)
   960  	case "422":
   961  		return fmt.Sprintf("( %s    - src.Rect.Min.Y  )*src.CStride + ((%s)/2 - src.Rect.Min.X/2)", y, x)
   962  	case "420":
   963  		return fmt.Sprintf("((%s)/2 - src.Rect.Min.Y/2)*src.CStride + ((%s)/2 - src.Rect.Min.X/2)", y, x)
   964  	case "440":
   965  		return fmt.Sprintf("((%s)/2 - src.Rect.Min.Y/2)*src.CStride + ( %s    - src.Rect.Min.X  )", y, x)
   966  	}
   967  	return fmt.Sprintf("unsupported sratio %q", sratio)
   968  }
   969  
   970  func ycbcrToRGB(lhs, tmp string) string {
   971  	s := `
   972  		// This is an inline version of image/color/ycbcr.go's YCbCr.RGBA method.
   973  		$yy1 := int(src.Y[$i]) * 0x10101
   974  		$cb1 := int(src.Cb[$j]) - 128
   975  		$cr1 := int(src.Cr[$j]) - 128
   976  		$r@ := ($yy1 + 91881*$cr1) >> 8
   977  		$g@ := ($yy1 - 22554*$cb1 - 46802*$cr1) >> 8
   978  		$b@ := ($yy1 + 116130*$cb1) >> 8
   979  		if $r@ < 0 {
   980  			$r@ = 0
   981  		} else if $r@ > 0xffff {
   982  			$r@ = 0xffff
   983  		}
   984  		if $g@ < 0 {
   985  			$g@ = 0
   986  		} else if $g@ > 0xffff {
   987  			$g@ = 0xffff
   988  		}
   989  		if $b@ < 0 {
   990  			$b@ = 0
   991  		} else if $b@ > 0xffff {
   992  			$b@ = 0xffff
   993  		}
   994  	`
   995  	s = strings.Replace(s, "$", lhs, -1)
   996  	s = strings.Replace(s, "@", tmp, -1)
   997  	return s
   998  }
   999  
  1000  func split(s, sep string) (string, string) {
  1001  	if i := strings.Index(s, sep); i >= 0 {
  1002  		return strings.TrimSpace(s[:i]), strings.TrimSpace(s[i+len(sep):])
  1003  	}
  1004  	return "", ""
  1005  }
  1006  
  1007  func splitEq(s string) (lhs, eqOp string) {
  1008  	s = strings.TrimSpace(s)
  1009  	if lhs, _ = split(s, ":="); lhs != "" {
  1010  		return lhs, ":="
  1011  	}
  1012  	if lhs, _ = split(s, "+="); lhs != "" {
  1013  		return lhs, "+="
  1014  	}
  1015  	return "", ""
  1016  }
  1017  
  1018  func splitArgs(s string) (args []string, extra string) {
  1019  	s = strings.TrimSpace(s)
  1020  	if s == "" || s[0] != '[' {
  1021  		return nil, ""
  1022  	}
  1023  	s = s[1:]
  1024  
  1025  	i := strings.IndexByte(s, ']')
  1026  	if i < 0 {
  1027  		return nil, ""
  1028  	}
  1029  	args, extra = strings.Split(s[:i], ","), s[i+1:]
  1030  	for i := range args {
  1031  		args[i] = strings.TrimSpace(args[i])
  1032  	}
  1033  	return args, extra
  1034  }
  1035  
  1036  func relName(s string) string {
  1037  	if i := strings.LastIndex(s, "."); i >= 0 {
  1038  		return s[i+1:]
  1039  	}
  1040  	return s
  1041  }
  1042  
  1043  const (
  1044  	codeRoot = `
  1045  		func (z $receiver) Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, op Op, opts *Options) {
  1046  			// Try to simplify a Scale to a Copy when DstMask is not specified.
  1047  			// If DstMask is not nil, Copy will call Scale back with same dr and sr, and cause stack overflow.
  1048  			if dr.Size() == sr.Size() && (opts == nil || opts.DstMask == nil) {
  1049  				Copy(dst, dr.Min, src, sr, op, opts)
  1050  				return
  1051  			}
  1052  
  1053  			var o Options
  1054  			if opts != nil {
  1055  				o = *opts
  1056  			}
  1057  
  1058  			// adr is the affected destination pixels.
  1059  			adr := dst.Bounds().Intersect(dr)
  1060  			adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
  1061  			if adr.Empty() || sr.Empty() {
  1062  				return
  1063  			}
  1064  			// Make adr relative to dr.Min.
  1065  			adr = adr.Sub(dr.Min)
  1066  			if op == Over && o.SrcMask == nil && opaque(src) {
  1067  				op = Src
  1068  			}
  1069  
  1070  			// sr is the source pixels. If it extends beyond the src bounds,
  1071  			// we cannot use the type-specific fast paths, as they access
  1072  			// the Pix fields directly without bounds checking.
  1073  			//
  1074  			// Similarly, the fast paths assume that the masks are nil.
  1075  			if o.DstMask != nil || o.SrcMask != nil || !sr.In(src.Bounds()) {
  1076  				switch op {
  1077  				case Over:
  1078  					z.scale_Image_Image_Over(dst, dr, adr, src, sr, &o)
  1079  				case Src:
  1080  					z.scale_Image_Image_Src(dst, dr, adr, src, sr, &o)
  1081  				}
  1082  			} else if _, ok := src.(*image.Uniform); ok {
  1083  				Draw(dst, dr, src, src.Bounds().Min, op)
  1084  			} else {
  1085  				$switch z.scale_$dTypeRN_$sTypeRN$sratio_$op(dst, dr, adr, src, sr, &o)
  1086  			}
  1087  		}
  1088  
  1089  		func (z $receiver) Transform(dst Image, s2d f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
  1090  			// Try to simplify a Transform to a Copy.
  1091  			if s2d[0] == 1 && s2d[1] == 0 && s2d[3] == 0 && s2d[4] == 1 {
  1092  				dx := int(s2d[2])
  1093  				dy := int(s2d[5])
  1094  				if float64(dx) == s2d[2] && float64(dy) == s2d[5] {
  1095  					Copy(dst, image.Point{X: sr.Min.X + dx, Y: sr.Min.X + dy}, src, sr, op, opts)
  1096  					return
  1097  				}
  1098  			}
  1099  
  1100  			var o Options
  1101  			if opts != nil {
  1102  				o = *opts
  1103  			}
  1104  
  1105  			dr := transformRect(&s2d, &sr)
  1106  			// adr is the affected destination pixels.
  1107  			adr := dst.Bounds().Intersect(dr)
  1108  			adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
  1109  			if adr.Empty() || sr.Empty() {
  1110  				return
  1111  			}
  1112  			if op == Over && o.SrcMask == nil && opaque(src) {
  1113  				op = Src
  1114  			}
  1115  
  1116  			d2s := invert(&s2d)
  1117  			// bias is a translation of the mapping from dst coordinates to src
  1118  			// coordinates such that the latter temporarily have non-negative X
  1119  			// and Y coordinates. This allows us to write int(f) instead of
  1120  			// int(math.Floor(f)), since "round to zero" and "round down" are
  1121  			// equivalent when f >= 0, but the former is much cheaper. The X--
  1122  			// and Y-- are because the TransformLeaf methods have a "sx -= 0.5"
  1123  			// adjustment.
  1124  			bias := transformRect(&d2s, &adr).Min
  1125  			bias.X--
  1126  			bias.Y--
  1127  			d2s[2] -= float64(bias.X)
  1128  			d2s[5] -= float64(bias.Y)
  1129  			// Make adr relative to dr.Min.
  1130  			adr = adr.Sub(dr.Min)
  1131  			// sr is the source pixels. If it extends beyond the src bounds,
  1132  			// we cannot use the type-specific fast paths, as they access
  1133  			// the Pix fields directly without bounds checking.
  1134  			//
  1135  			// Similarly, the fast paths assume that the masks are nil.
  1136  			if o.DstMask != nil || o.SrcMask != nil || !sr.In(src.Bounds()) {
  1137  				switch op {
  1138  				case Over:
  1139  					z.transform_Image_Image_Over(dst, dr, adr, &d2s, src, sr, bias, &o)
  1140  				case Src:
  1141  					z.transform_Image_Image_Src(dst, dr, adr, &d2s, src, sr, bias, &o)
  1142  				}
  1143  			} else if u, ok := src.(*image.Uniform); ok {
  1144  				transform_Uniform(dst, dr, adr, &d2s, u, sr, bias, op)
  1145  			} else {
  1146  				$switch z.transform_$dTypeRN_$sTypeRN$sratio_$op(dst, dr, adr, &d2s, src, sr, bias, &o)
  1147  			}
  1148  		}
  1149  	`
  1150  
  1151  	codeNNScaleLeaf = `
  1152  		func (nnInterpolator) scale_$dTypeRN_$sTypeRN$sratio_$op(dst $dType, dr, adr image.Rectangle, src $sType, sr image.Rectangle, opts *Options) {
  1153  			dw2 := uint64(dr.Dx()) * 2
  1154  			dh2 := uint64(dr.Dy()) * 2
  1155  			sw := uint64(sr.Dx())
  1156  			sh := uint64(sr.Dy())
  1157  			$preOuter
  1158  			for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
  1159  				sy := (2*uint64(dy) + 1) * sh / dh2
  1160  				$preInner
  1161  				for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ { $tweakDx
  1162  					sx := (2*uint64(dx) + 1) * sw / dw2
  1163  					p := $srcu[sr.Min.X + int(sx), sr.Min.Y + int(sy)]
  1164  					$outputu[dr.Min.X + int(dx), dr.Min.Y + int(dy), p]
  1165  				}
  1166  			}
  1167  		}
  1168  	`
  1169  
  1170  	codeNNTransformLeaf = `
  1171  		func (nnInterpolator) transform_$dTypeRN_$sTypeRN$sratio_$op(dst $dType, dr, adr image.Rectangle, d2s *f64.Aff3, src $sType, sr image.Rectangle, bias image.Point, opts *Options) {
  1172  			$preOuter
  1173  			for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
  1174  				dyf := float64(dr.Min.Y + int(dy)) + 0.5
  1175  				$preInner
  1176  				for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ { $tweakDx
  1177  					dxf := float64(dr.Min.X + int(dx)) + 0.5
  1178  					sx0 := int(d2s[0]*dxf + d2s[1]*dyf + d2s[2]) + bias.X
  1179  					sy0 := int(d2s[3]*dxf + d2s[4]*dyf + d2s[5]) + bias.Y
  1180  					if !(image.Point{sx0, sy0}).In(sr) {
  1181  						continue
  1182  					}
  1183  					p := $srcu[sx0, sy0]
  1184  					$outputu[dr.Min.X + int(dx), dr.Min.Y + int(dy), p]
  1185  				}
  1186  			}
  1187  		}
  1188  	`
  1189  
  1190  	codeABLScaleLeaf = `
  1191  		func (ablInterpolator) scale_$dTypeRN_$sTypeRN$sratio_$op(dst $dType, dr, adr image.Rectangle, src $sType, sr image.Rectangle, opts *Options) {
  1192  			sw := int32(sr.Dx())
  1193  			sh := int32(sr.Dy())
  1194  			yscale := float64(sh) / float64(dr.Dy())
  1195  			xscale := float64(sw) / float64(dr.Dx())
  1196  			swMinus1, shMinus1 := sw - 1, sh - 1
  1197  			$preOuter
  1198  
  1199  			for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
  1200  				sy := (float64(dy)+0.5)*yscale - 0.5
  1201  				// If sy < 0, we will clamp sy0 to 0 anyway, so it doesn't matter if
  1202  				// we say int32(sy) instead of int32(math.Floor(sy)). Similarly for
  1203  				// sx, below.
  1204  				sy0 := int32(sy)
  1205  				yFrac0 := sy - float64(sy0)
  1206  				yFrac1 := 1 - yFrac0
  1207  				sy1 := sy0 + 1
  1208  				if sy < 0 {
  1209  					sy0, sy1 = 0, 0
  1210  					yFrac0, yFrac1 = 0, 1
  1211  				} else if sy1 > shMinus1 {
  1212  					sy0, sy1 = shMinus1, shMinus1
  1213  					yFrac0, yFrac1 = 1, 0
  1214  				}
  1215  				$preInner
  1216  
  1217  				for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ { $tweakDx
  1218  					sx := (float64(dx)+0.5)*xscale - 0.5
  1219  					sx0 := int32(sx)
  1220  					xFrac0 := sx - float64(sx0)
  1221  					xFrac1 := 1 - xFrac0
  1222  					sx1 := sx0 + 1
  1223  					if sx < 0 {
  1224  						sx0, sx1 = 0, 0
  1225  						xFrac0, xFrac1 = 0, 1
  1226  					} else if sx1 > swMinus1 {
  1227  						sx0, sx1 = swMinus1, swMinus1
  1228  						xFrac0, xFrac1 = 1, 0
  1229  					}
  1230  
  1231  					s00 := $srcf[sr.Min.X + int(sx0), sr.Min.Y + int(sy0)]
  1232  					s10 := $srcf[sr.Min.X + int(sx1), sr.Min.Y + int(sy0)]
  1233  					$blend[xFrac1, s00, xFrac0, s10]
  1234  					s01 := $srcf[sr.Min.X + int(sx0), sr.Min.Y + int(sy1)]
  1235  					s11 := $srcf[sr.Min.X + int(sx1), sr.Min.Y + int(sy1)]
  1236  					$blend[xFrac1, s01, xFrac0, s11]
  1237  					$blend[yFrac1, s10, yFrac0, s11]
  1238  					$convFtou[p, s11]
  1239  					$outputu[dr.Min.X + int(dx), dr.Min.Y + int(dy), p]
  1240  				}
  1241  			}
  1242  		}
  1243  	`
  1244  
  1245  	codeABLTransformLeaf = `
  1246  		func (ablInterpolator) transform_$dTypeRN_$sTypeRN$sratio_$op(dst $dType, dr, adr image.Rectangle, d2s *f64.Aff3, src $sType, sr image.Rectangle, bias image.Point, opts *Options) {
  1247  			$preOuter
  1248  			for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
  1249  				dyf := float64(dr.Min.Y + int(dy)) + 0.5
  1250  				$preInner
  1251  				for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ { $tweakDx
  1252  					dxf := float64(dr.Min.X + int(dx)) + 0.5
  1253  					sx := d2s[0]*dxf + d2s[1]*dyf + d2s[2]
  1254  					sy := d2s[3]*dxf + d2s[4]*dyf + d2s[5]
  1255  					if !(image.Point{int(sx) + bias.X, int(sy) + bias.Y}).In(sr) {
  1256  						continue
  1257  					}
  1258  
  1259  					sx -= 0.5
  1260  					sx0 := int(sx)
  1261  					xFrac0 := sx - float64(sx0)
  1262  					xFrac1 := 1 - xFrac0
  1263  					sx0 += bias.X
  1264  					sx1 := sx0 + 1
  1265  					if sx0 < sr.Min.X {
  1266  						sx0, sx1 = sr.Min.X, sr.Min.X
  1267  						xFrac0, xFrac1 = 0, 1
  1268  					} else if sx1 >= sr.Max.X {
  1269  						sx0, sx1 = sr.Max.X-1, sr.Max.X-1
  1270  						xFrac0, xFrac1 = 1, 0
  1271  					}
  1272  
  1273  					sy -= 0.5
  1274  					sy0 := int(sy)
  1275  					yFrac0 := sy - float64(sy0)
  1276  					yFrac1 := 1 - yFrac0
  1277  					sy0 += bias.Y
  1278  					sy1 := sy0 + 1
  1279  					if sy0 < sr.Min.Y {
  1280  						sy0, sy1 = sr.Min.Y, sr.Min.Y
  1281  						yFrac0, yFrac1 = 0, 1
  1282  					} else if sy1 >= sr.Max.Y {
  1283  						sy0, sy1 = sr.Max.Y-1, sr.Max.Y-1
  1284  						yFrac0, yFrac1 = 1, 0
  1285  					}
  1286  
  1287  					s00 := $srcf[sx0, sy0]
  1288  					s10 := $srcf[sx1, sy0]
  1289  					$blend[xFrac1, s00, xFrac0, s10]
  1290  					s01 := $srcf[sx0, sy1]
  1291  					s11 := $srcf[sx1, sy1]
  1292  					$blend[xFrac1, s01, xFrac0, s11]
  1293  					$blend[yFrac1, s10, yFrac0, s11]
  1294  					$convFtou[p, s11]
  1295  					$outputu[dr.Min.X + int(dx), dr.Min.Y + int(dy), p]
  1296  				}
  1297  			}
  1298  		}
  1299  	`
  1300  
  1301  	codeKernelRoot = `
  1302  		func (z *kernelScaler) Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, op Op, opts *Options) {
  1303  			if z.dw != int32(dr.Dx()) || z.dh != int32(dr.Dy()) || z.sw != int32(sr.Dx()) || z.sh != int32(sr.Dy()) {
  1304  				z.kernel.Scale(dst, dr, src, sr, op, opts)
  1305  				return
  1306  			}
  1307  
  1308  			var o Options
  1309  			if opts != nil {
  1310  				o = *opts
  1311  			}
  1312  
  1313  			// adr is the affected destination pixels.
  1314  			adr := dst.Bounds().Intersect(dr)
  1315  			adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
  1316  			if adr.Empty() || sr.Empty() {
  1317  				return
  1318  			}
  1319  			// Make adr relative to dr.Min.
  1320  			adr = adr.Sub(dr.Min)
  1321  			if op == Over && o.SrcMask == nil && opaque(src) {
  1322  				op = Src
  1323  			}
  1324  
  1325  			if _, ok := src.(*image.Uniform); ok && o.DstMask == nil && o.SrcMask == nil && sr.In(src.Bounds()) {
  1326  				Draw(dst, dr, src, src.Bounds().Min, op)
  1327  				return
  1328  			}
  1329  
  1330  			// Create a temporary buffer:
  1331  			// scaleX distributes the source image's columns over the temporary image.
  1332  			// scaleY distributes the temporary image's rows over the destination image.
  1333  			var tmp [][4]float64
  1334  			if z.pool.New != nil {
  1335  				tmpp := z.pool.Get().(*[][4]float64)
  1336  				defer z.pool.Put(tmpp)
  1337  				tmp = *tmpp
  1338  			} else {
  1339  				tmp = z.makeTmpBuf()
  1340  			}
  1341  
  1342  			// sr is the source pixels. If it extends beyond the src bounds,
  1343  			// we cannot use the type-specific fast paths, as they access
  1344  			// the Pix fields directly without bounds checking.
  1345  			//
  1346  			// Similarly, the fast paths assume that the masks are nil.
  1347  			if o.SrcMask != nil || !sr.In(src.Bounds()) {
  1348  				z.scaleX_Image(tmp, src, sr, &o)
  1349  			} else {
  1350  				$switchS z.scaleX_$sTypeRN$sratio(tmp, src, sr, &o)
  1351  			}
  1352  
  1353  			if o.DstMask != nil {
  1354  				switch op {
  1355  				case Over:
  1356  					z.scaleY_Image_Over(dst, dr, adr, tmp, &o)
  1357  				case Src:
  1358  					z.scaleY_Image_Src(dst, dr, adr, tmp, &o)
  1359  				}
  1360  			} else {
  1361  				$switchD z.scaleY_$dTypeRN_$op(dst, dr, adr, tmp, &o)
  1362  			}
  1363  		}
  1364  
  1365  		func (q *Kernel) Transform(dst Image, s2d f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
  1366  			var o Options
  1367  			if opts != nil {
  1368  				o = *opts
  1369  			}
  1370  
  1371  			dr := transformRect(&s2d, &sr)
  1372  			// adr is the affected destination pixels.
  1373  			adr := dst.Bounds().Intersect(dr)
  1374  			adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
  1375  			if adr.Empty() || sr.Empty() {
  1376  				return
  1377  			}
  1378  			if op == Over && o.SrcMask == nil && opaque(src) {
  1379  				op = Src
  1380  			}
  1381  			d2s := invert(&s2d)
  1382  			// bias is a translation of the mapping from dst coordinates to src
  1383  			// coordinates such that the latter temporarily have non-negative X
  1384  			// and Y coordinates. This allows us to write int(f) instead of
  1385  			// int(math.Floor(f)), since "round to zero" and "round down" are
  1386  			// equivalent when f >= 0, but the former is much cheaper. The X--
  1387  			// and Y-- are because the TransformLeaf methods have a "sx -= 0.5"
  1388  			// adjustment.
  1389  			bias := transformRect(&d2s, &adr).Min
  1390  			bias.X--
  1391  			bias.Y--
  1392  			d2s[2] -= float64(bias.X)
  1393  			d2s[5] -= float64(bias.Y)
  1394  			// Make adr relative to dr.Min.
  1395  			adr = adr.Sub(dr.Min)
  1396  
  1397  			if u, ok := src.(*image.Uniform); ok && o.DstMask != nil && o.SrcMask != nil && sr.In(src.Bounds()) {
  1398  				transform_Uniform(dst, dr, adr, &d2s, u, sr, bias, op)
  1399  				return
  1400  			}
  1401  
  1402  			xscale := abs(d2s[0])
  1403  			if s := abs(d2s[1]); xscale < s {
  1404  				xscale = s
  1405  			}
  1406  			yscale := abs(d2s[3])
  1407  			if s := abs(d2s[4]); yscale < s {
  1408  				yscale = s
  1409  			}
  1410  
  1411  			// sr is the source pixels. If it extends beyond the src bounds,
  1412  			// we cannot use the type-specific fast paths, as they access
  1413  			// the Pix fields directly without bounds checking.
  1414  			//
  1415  			// Similarly, the fast paths assume that the masks are nil.
  1416  			if o.DstMask != nil || o.SrcMask != nil || !sr.In(src.Bounds()) {
  1417  				switch op {
  1418  				case Over:
  1419  					q.transform_Image_Image_Over(dst, dr, adr, &d2s, src, sr, bias, xscale, yscale, &o)
  1420  				case Src:
  1421  					q.transform_Image_Image_Src(dst, dr, adr, &d2s, src, sr, bias, xscale, yscale, &o)
  1422  				}
  1423  			} else {
  1424  				$switch q.transform_$dTypeRN_$sTypeRN$sratio_$op(dst, dr, adr, &d2s, src, sr, bias, xscale, yscale, &o)
  1425  			}
  1426  		}
  1427  	`
  1428  
  1429  	codeKernelScaleLeafX = `
  1430  		func (z *kernelScaler) scaleX_$sTypeRN$sratio(tmp [][4]float64, src $sType, sr image.Rectangle, opts *Options) {
  1431  			t := 0
  1432  			$preKernelOuter
  1433  			for y := int32(0); y < z.sh; y++ {
  1434  				for _, s := range z.horizontal.sources {
  1435  					var pr, pg, pb, pa float64 $tweakVarP
  1436  					for _, c := range z.horizontal.contribs[s.i:s.j] {
  1437  						p += $srcf[sr.Min.X + int(c.coord), sr.Min.Y + int(y)] * c.weight
  1438  					}
  1439  					$tweakPr
  1440  					tmp[t] = [4]float64{
  1441  						pr * s.invTotalWeightFFFF, $tweakP
  1442  						pg * s.invTotalWeightFFFF, $tweakP
  1443  						pb * s.invTotalWeightFFFF, $tweakP
  1444  						pa * s.invTotalWeightFFFF, $tweakP
  1445  					}
  1446  					t++
  1447  				}
  1448  			}
  1449  		}
  1450  	`
  1451  
  1452  	codeKernelScaleLeafY = `
  1453  		func (z *kernelScaler) scaleY_$dTypeRN_$op(dst $dType, dr, adr image.Rectangle, tmp [][4]float64, opts *Options) {
  1454  			$preOuter
  1455  			for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ {
  1456  				$preKernelInner
  1457  				for dy, s := range z.vertical.sources[adr.Min.Y:adr.Max.Y] { $tweakDy
  1458  					var pr, pg, pb, pa float64
  1459  					for _, c := range z.vertical.contribs[s.i:s.j] {
  1460  						p := &tmp[c.coord*z.dw+dx]
  1461  						pr += p[0] * c.weight
  1462  						pg += p[1] * c.weight
  1463  						pb += p[2] * c.weight
  1464  						pa += p[3] * c.weight
  1465  					}
  1466  					$clampToAlpha
  1467  					$outputf[dr.Min.X + int(dx), dr.Min.Y + int(adr.Min.Y + dy), ftou, p, s.invTotalWeight]
  1468  					$tweakD
  1469  				}
  1470  			}
  1471  		}
  1472  	`
  1473  
  1474  	codeKernelTransformLeaf = `
  1475  		func (q *Kernel) transform_$dTypeRN_$sTypeRN$sratio_$op(dst $dType, dr, adr image.Rectangle, d2s *f64.Aff3, src $sType, sr image.Rectangle, bias image.Point, xscale, yscale float64, opts *Options) {
  1476  			// When shrinking, broaden the effective kernel support so that we still
  1477  			// visit every source pixel.
  1478  			xHalfWidth, xKernelArgScale := q.Support, 1.0
  1479  			if xscale > 1 {
  1480  				xHalfWidth *= xscale
  1481  				xKernelArgScale = 1 / xscale
  1482  			}
  1483  			yHalfWidth, yKernelArgScale := q.Support, 1.0
  1484  			if yscale > 1 {
  1485  				yHalfWidth *= yscale
  1486  				yKernelArgScale = 1 / yscale
  1487  			}
  1488  
  1489  			xWeights := make([]float64, 1 + 2*int(math.Ceil(xHalfWidth)))
  1490  			yWeights := make([]float64, 1 + 2*int(math.Ceil(yHalfWidth)))
  1491  
  1492  			$preOuter
  1493  			for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
  1494  				dyf := float64(dr.Min.Y + int(dy)) + 0.5
  1495  				$preInner
  1496  				for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ { $tweakDx
  1497  					dxf := float64(dr.Min.X + int(dx)) + 0.5
  1498  					sx := d2s[0]*dxf + d2s[1]*dyf + d2s[2]
  1499  					sy := d2s[3]*dxf + d2s[4]*dyf + d2s[5]
  1500  					if !(image.Point{int(sx) + bias.X, int(sy) + bias.Y}).In(sr) {
  1501  						continue
  1502  					}
  1503  
  1504  					// TODO: adjust the bias so that we can use int(f) instead
  1505  					// of math.Floor(f) and math.Ceil(f).
  1506  					sx += float64(bias.X)
  1507  					sx -= 0.5
  1508  					ix := int(math.Floor(sx - xHalfWidth))
  1509  					if ix < sr.Min.X {
  1510  						ix = sr.Min.X
  1511  					}
  1512  					jx := int(math.Ceil(sx + xHalfWidth))
  1513  					if jx > sr.Max.X {
  1514  						jx = sr.Max.X
  1515  					}
  1516  
  1517  					totalXWeight := 0.0
  1518  					for kx := ix; kx < jx; kx++ {
  1519  						xWeight := 0.0
  1520  						if t := abs((sx - float64(kx)) * xKernelArgScale); t < q.Support {
  1521  							xWeight = q.At(t)
  1522  						}
  1523  						xWeights[kx - ix] = xWeight
  1524  						totalXWeight += xWeight
  1525  					}
  1526  					for x := range xWeights[:jx-ix] {
  1527  						xWeights[x] /= totalXWeight
  1528  					}
  1529  
  1530  					sy += float64(bias.Y)
  1531  					sy -= 0.5
  1532  					iy := int(math.Floor(sy - yHalfWidth))
  1533  					if iy < sr.Min.Y {
  1534  						iy = sr.Min.Y
  1535  					}
  1536  					jy := int(math.Ceil(sy + yHalfWidth))
  1537  					if jy > sr.Max.Y {
  1538  						jy = sr.Max.Y
  1539  					}
  1540  
  1541  					totalYWeight := 0.0
  1542  					for ky := iy; ky < jy; ky++ {
  1543  						yWeight := 0.0
  1544  						if t := abs((sy - float64(ky)) * yKernelArgScale); t < q.Support {
  1545  							yWeight = q.At(t)
  1546  						}
  1547  						yWeights[ky - iy] = yWeight
  1548  						totalYWeight += yWeight
  1549  					}
  1550  					for y := range yWeights[:jy-iy] {
  1551  						yWeights[y] /= totalYWeight
  1552  					}
  1553  
  1554  					var pr, pg, pb, pa float64 $tweakVarP
  1555  					for ky := iy; ky < jy; ky++ {
  1556  						if yWeight := yWeights[ky - iy]; yWeight != 0 {
  1557  							for kx := ix; kx < jx; kx++ {
  1558  								if w := xWeights[kx - ix] * yWeight; w != 0 {
  1559  									p += $srcf[kx, ky] * w
  1560  								}
  1561  							}
  1562  						}
  1563  					}
  1564  					$clampToAlpha
  1565  					$outputf[dr.Min.X + int(dx), dr.Min.Y + int(dy), fffftou, p, 1]
  1566  				}
  1567  			}
  1568  		}
  1569  	`
  1570  )
  1571  

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