main.go

Documentation: github.com/golang/freetype/example/gamma

     1  // Copyright 2010 The Freetype-Go Authors. All rights reserved.
     2  // Use of this source code is governed by your choice of either the
     3  // FreeType License or the GNU General Public License version 2 (or
     4  // any later version), both of which can be found in the LICENSE file.
     5  
     6  // +build example
     7  //
     8  // This build tag means that "go install github.com/golang/freetype/..."
     9  // doesn't install this example program. Use "go run main.go" to run it or "go
    10  // install -tags=example" to install it.
    11  
    12  package main
    13  
    14  import (
    15  	"bufio"
    16  	"fmt"
    17  	"image"
    18  	"image/draw"
    19  	"image/png"
    20  	"log"
    21  	"os"
    22  
    23  	"github.com/golang/freetype/raster"
    24  	"golang.org/x/image/math/fixed"
    25  )
    26  
    27  func p(x, y int) fixed.Point26_6 {
    28  	return fixed.Point26_6{
    29  		X: fixed.Int26_6(x * 64),
    30  		Y: fixed.Int26_6(y * 64),
    31  	}
    32  }
    33  
    34  func main() {
    35  	// Draw a rounded corner that is one pixel wide.
    36  	r := raster.NewRasterizer(50, 50)
    37  	r.Start(p(5, 5))
    38  	r.Add1(p(5, 25))
    39  	r.Add2(p(5, 45), p(25, 45))
    40  	r.Add1(p(45, 45))
    41  	r.Add1(p(45, 44))
    42  	r.Add1(p(26, 44))
    43  	r.Add2(p(6, 44), p(6, 24))
    44  	r.Add1(p(6, 5))
    45  	r.Add1(p(5, 5))
    46  
    47  	// Rasterize that curve multiple times at different gammas.
    48  	const (
    49  		w = 600
    50  		h = 200
    51  	)
    52  	rgba := image.NewRGBA(image.Rect(0, 0, w, h))
    53  	draw.Draw(rgba, image.Rect(0, 0, w, h/2), image.Black, image.ZP, draw.Src)
    54  	draw.Draw(rgba, image.Rect(0, h/2, w, h), image.White, image.ZP, draw.Src)
    55  	mask := image.NewAlpha(image.Rect(0, 0, 50, 50))
    56  	painter := raster.NewAlphaSrcPainter(mask)
    57  	gammas := []float64{1.0 / 10.0, 1.0 / 3.0, 1.0 / 2.0, 2.0 / 3.0, 4.0 / 5.0, 1.0, 5.0 / 4.0, 3.0 / 2.0, 2.0, 3.0, 10.0}
    58  	for i, g := range gammas {
    59  		draw.Draw(mask, mask.Bounds(), image.Transparent, image.ZP, draw.Src)
    60  		r.Rasterize(raster.NewGammaCorrectionPainter(painter, g))
    61  		x, y := 50*i+25, 25
    62  		draw.DrawMask(rgba, image.Rect(x, y, x+50, y+50), image.White, image.ZP, mask, image.ZP, draw.Over)
    63  		y += 100
    64  		draw.DrawMask(rgba, image.Rect(x, y, x+50, y+50), image.Black, image.ZP, mask, image.ZP, draw.Over)
    65  	}
    66  
    67  	// Save that RGBA image to disk.
    68  	outFile, err := os.Create("out.png")
    69  	if err != nil {
    70  		log.Println(err)
    71  		os.Exit(1)
    72  	}
    73  	defer outFile.Close()
    74  	b := bufio.NewWriter(outFile)
    75  	err = png.Encode(b, rgba)
    76  	if err != nil {
    77  		log.Println(err)
    78  		os.Exit(1)
    79  	}
    80  	err = b.Flush()
    81  	if err != nil {
    82  		log.Println(err)
    83  		os.Exit(1)
    84  	}
    85  	fmt.Println("Wrote out.png OK.")
    86  }
    87
View as plain text