Created
September 20, 2013 10:18
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a gift to 15.Aug moon
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// 8.15 project main.go | |
// generate a pic of moon | |
package main | |
import ( | |
"fmt" | |
"image" | |
"image/color" | |
"image/draw" | |
"image/png" | |
"os" | |
) | |
func drawCircle(img draw.Image, x, y, radius int, fill color.Color) { | |
// Algorithm taken from | |
// http://en.wikipedia.org/wiki/Midpoint_circle_algorithm | |
x0, y0 := x, y | |
f := 1 - radius | |
ddF_x, ddF_y := 1, -2*radius | |
x, y = 0, radius | |
img.Set(x0, y0+radius, fill) | |
img.Set(x0, y0-radius, fill) | |
img.Set(x0+radius, y0, fill) | |
img.Set(x0-radius, y0, fill) | |
for x < y { | |
if f >= 0 { | |
y-- | |
ddF_y += 2 | |
f += ddF_y | |
} | |
x++ | |
ddF_x += 2 | |
f += ddF_x | |
img.Set(x0+x, y0+y, fill) | |
img.Set(x0-x, y0+y, fill) | |
img.Set(x0+x, y0-y, fill) | |
img.Set(x0-x, y0-y, fill) | |
img.Set(x0+y, y0+x, fill) | |
img.Set(x0-y, y0+x, fill) | |
img.Set(x0+y, y0-x, fill) | |
img.Set(x0-y, y0-x, fill) | |
} | |
} | |
func main() { | |
fd, err := os.Create("15.png") | |
if err != nil { | |
fmt.Println("create file failed") | |
return | |
} | |
defer fd.Close() | |
img := image.NewRGBA(image.Rect(0, 0, 400, 300)) | |
draw.Draw(img, img.Bounds(), &image.Uniform{color.Black}, image.ZP, draw.Src) | |
drawCircle(img, 100, 100, 50, color.White) | |
png.Encode(fd, img) | |
fmt.Println("Hello World!") | |
} |
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