freetype/example/gamma/main.go

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// Copyright 2010 The Freetype-Go Authors. All rights reserved.
// Use of this source code is governed by your choice of either the
// FreeType License or the GNU General Public License version 2,
// both of which can be found in the LICENSE file.
package main
import (
"bufio"
"exp/draw"
"fmt"
"image"
"image/png"
"log"
"os"
"freetype-go.googlecode.com/hg/freetype/raster"
)
func p(x, y int) raster.Point {
return raster.Point{raster.Fixed(x * 256), raster.Fixed(y * 256)}
}
func clear(m *image.Alpha) {
for y := 0; y < m.Height(); y++ {
for x := 0; x < m.Width(); x++ {
m.Pixel[y][x] = image.AlphaColor{0}
}
}
}
func main() {
// Draw a rounded corner that is one pixel wide.
r := raster.NewRasterizer(50, 50)
r.Start(p(5, 5))
r.Add1(p(5, 25))
r.Add2(p(5, 45), p(25, 45))
r.Add1(p(45, 45))
r.Add1(p(45, 44))
r.Add1(p(26, 44))
r.Add2(p(6, 44), p(6, 24))
r.Add1(p(6, 5))
r.Add1(p(5, 5))
// Rasterize that curve multiple times at different gammas.
const (
w = 600
h = 200
)
rgba := image.NewRGBA(w, h)
draw.Draw(rgba, draw.Rect(0, 0, w, h/2), image.Black, draw.ZP)
draw.Draw(rgba, draw.Rect(0, h/2, w, h), image.White, draw.ZP)
mask := image.NewAlpha(50, 50)
painter := raster.NewAlphaPainter(mask)
painter.Op = draw.Src
gammas := []float{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}
for i, g := range gammas {
clear(mask)
r.Rasterize(raster.NewGammaCorrectionPainter(painter, g))
x, y := 50*i+25, 25
draw.DrawMask(rgba, draw.Rect(x, y, x+50, y+50), image.White, draw.ZP, mask, draw.ZP, draw.Over)
y += 100
draw.DrawMask(rgba, draw.Rect(x, y, x+50, y+50), image.Black, draw.ZP, mask, draw.ZP, draw.Over)
}
// Save that RGBA image to disk.
f, err := os.Open("out.png", os.O_CREAT|os.O_WRONLY, 0600)
if err != nil {
log.Stderr(err)
os.Exit(1)
}
defer f.Close()
b := bufio.NewWriter(f)
err = png.Encode(b, rgba)
if err != nil {
log.Stderr(err)
os.Exit(1)
}
err = b.Flush()
if err != nil {
log.Stderr(err)
os.Exit(1)
}
fmt.Println("Wrote out.png OK.")
}