A captcha.go

@@ -0,0 +1,268 @@
+package main
+
+import (
+	"image"
+	"image/png"
+	"os"
+	"rand"
+	"time"
+	crand "crypto/rand"
+	"io"
+)
+
+var numbers = [][]byte{
+	{
+		0, 1, 1, 1, 0,
+		1, 0, 0, 0, 1,
+		1, 0, 0, 0, 1,
+		1, 0, 0, 0, 1,
+		1, 0, 0, 0, 1,
+		1, 0, 0, 0, 1,
+		1, 0, 0, 0, 1,
+		0, 1, 1, 1, 0,
+	},
+	{
+		0, 0, 1, 0, 0,
+		0, 1, 1, 0, 0,
+		1, 0, 1, 0, 0,
+		0, 0, 1, 0, 0,
+		0, 0, 1, 0, 0,
+		0, 0, 1, 0, 0,
+		0, 0, 1, 0, 0,
+		1, 1, 1, 1, 1,
+	},
+	{
+		0, 1, 1, 1, 0,
+		1, 0, 0, 0, 1,
+		0, 0, 0, 0, 1,
+		0, 0, 0, 1, 1,
+		0, 1, 1, 0, 0,
+		1, 0, 0, 0, 0,
+		1, 0, 0, 0, 0,
+		1, 1, 1, 1, 1,
+	},
+	{
+		1, 1, 1, 1, 1,
+		0, 0, 0, 0, 1,
+		0, 0, 0, 1, 1,
+		0, 1, 1, 0, 0,
+		0, 0, 0, 1, 0,
+		0, 0, 0, 0, 1,
+		0, 0, 0, 0, 1,
+		1, 1, 1, 1, 0,
+	},
+	{
+		1, 0, 0, 1, 0,
+		1, 0, 0, 1, 0,
+		1, 0, 0, 1, 0,
+		1, 0, 0, 1, 0,
+		1, 1, 1, 1, 1,
+		0, 0, 0, 1, 0,
+		0, 0, 0, 1, 0,
+		0, 0, 0, 1, 0,
+	},
+	{
+		1, 1, 1, 1, 1,
+		1, 0, 0, 0, 0,
+		1, 0, 0, 0, 0,
+		1, 1, 1, 1, 0,
+		0, 0, 0, 1, 1,
+		0, 0, 0, 0, 1,
+		0, 0, 0, 1, 1,
+		1, 1, 1, 1, 0,
+	},
+	{
+		0, 0, 1, 1, 1,
+		0, 1, 0, 0, 0,
+		1, 0, 0, 0, 0,
+		1, 1, 1, 1, 0,
+		1, 1, 0, 0, 1,
+		1, 0, 0, 0, 1,
+		1, 1, 0, 0, 1,
+		0, 1, 1, 1, 0,
+	},
+	{
+		1, 1, 1, 1, 1,
+		0, 0, 0, 0, 1,
+		0, 0, 0, 0, 1,
+		0, 0, 0, 1, 0,
+		0, 0, 1, 0, 0,
+		0, 1, 0, 0, 0,
+		0, 1, 0, 0, 0,
+		0, 1, 0, 0, 0,
+	},
+	{
+		0, 1, 1, 1, 0,
+		1, 0, 0, 0, 1,
+		1, 1, 0, 1, 1,
+		0, 1, 1, 1, 0,
+		1, 1, 0, 1, 1,
+		1, 0, 0, 0, 1,
+		1, 1, 0, 1, 1,
+		0, 1, 1, 1, 0,
+	},
+	{
+		0, 1, 1, 1, 0,
+		1, 0, 0, 1, 1,
+		1, 0, 0, 0, 1,
+		1, 1, 0, 0, 1,
+		0, 1, 1, 1, 1,
+		0, 0, 0, 0, 1,
+		0, 0, 0, 0, 1,
+		1, 1, 1, 1, 0,
+	},
+}
+
+const (
+	NumberWidth  = 5
+	NumberHeight = 8
+	DotSize = 6
+	SkewFactor = 3
+)
+
+func drawHorizLine(img *image.NRGBA, color image.Color, fromX, toX, y int) {
+	for x := fromX; x <= toX; x++ {
+		img.Set(x, y, color)
+	}
+}
+
+func drawCircle(img *image.NRGBA, color image.Color, x0, y0, radius int) {
+	f := 1 - radius
+	ddF_x := 1
+	ddF_y := -2 * radius
+	x := 0
+	y := radius
+
+	img.Set(x0, y0+radius, color)
+	img.Set(x0, y0-radius, color)
+	//img.Set(x0+radius, y0, color)
+	//img.Set(x0-radius, y0, color)
+	drawHorizLine(img, color, x0-radius, x0+radius, y0)
+
+	for x < y {
+		// ddF_x == 2 * x + 1;
+		// ddF_y == -2 * y;
+		// f == x*x + y*y - radius*radius + 2*x - y + 1;
+		if f >= 0 {
+			y--
+			ddF_y += 2
+			f += ddF_y
+		}
+		x++
+		ddF_x += 2
+		f += ddF_x
+		//img.Set(x0+x, y0+y, color)
+		//img.Set(x0-x, y0+y, color)
+		drawHorizLine(img, color, x0-x, x0+x, y0+y)
+		//img.Set(x0+x, y0-y, color)
+		//img.Set(x0-x, y0-y, color)
+		drawHorizLine(img, color, x0-x, x0+x, y0-y)
+		//img.Set(x0+y, y0+x, color)
+		//img.Set(x0-y, y0+x, color)
+		drawHorizLine(img, color, x0-y, x0+y, y0+x)
+		//img.Set(x0+y, y0-x, color)
+		//img.Set(x0-y, y0-x, color)
+		drawHorizLine(img, color, x0-y, x0+y, y0-x)
+	}
+}
+
+func min3(x, y, z uint8) (o uint8) {
+	o = x
+	if y < o {
+		o = y
+	}
+	if z < o {
+		o = z
+	}
+	return
+}
+
+func max3(x, y, z uint8) (o uint8) {
+	o = x
+	if y > o {
+		o = y
+	}
+	if z > o {
+		o = z
+	}
+	return
+}
+
+func setRandomBrightness(c *image.NRGBAColor, max uint8) {
+	minc := min3(c.R, c.G, c.B)
+	maxc := max3(c.R, c.G, c.B)
+	if maxc > max {
+		return
+	}
+	n := rand.Intn(int(max-maxc)) - int(minc)
+	c.R = uint8(int(c.R) + n)
+	c.G = uint8(int(c.G) + n)
+	c.B = uint8(int(c.B) + n)
+}
+
+func fillWithCircles(img *image.NRGBA, n, maxradius int) {
+	maxx := img.Bounds().Max.X
+	maxy := img.Bounds().Max.Y
+	color := image.NRGBAColor{0, 0, 0x80, 0xFF}
+	for i := 0; i < n; i++ {
+		setRandomBrightness(&color, 255)
+		r := rand.Intn(maxradius-1)+1 
+		drawCircle(img, color, rand.Intn(maxx-r*2)+r, rand.Intn(maxy-r*2)+r, r)
+	}
+}
+
+func drawNumber(img *image.NRGBA, number []byte, x, y int, color image.NRGBAColor) {
+	skf := rand.Intn(SkewFactor)-SkewFactor/2
+	if skf < 0 {
+		x -= skf * NumberHeight
+	}
+	for y0 := 0; y0 < NumberHeight; y0++ {
+		for x0 := 0; x0 < NumberWidth; x0++ {
+			radius := rand.Intn(DotSize/2)+DotSize/2
+			addx := rand.Intn(radius/2)
+			addy := rand.Intn(radius/2)
+			if number[y0*NumberWidth+x0] == 1 {
+				drawCircle(img, color, x+x0*DotSize+DotSize+addx, y+y0*DotSize+DotSize+addy, radius)
+			}
+		}
+		x += skf
+	}
+}
+
+func drawNumbersToImage(ns []byte) {
+	img := image.NewNRGBA(NumberWidth*(DotSize+2)*len(ns)+DotSize, NumberHeight*DotSize+(DotSize*6))
+	for y := 0; y < img.Bounds().Max.Y; y++ {
+		for x := 0; x < img.Bounds().Max.X; x++ {
+			img.Set(x, y, image.NRGBAColor{0xFF, 0xFF, 0xFF, 0xFF})
+		}
+	}
+	fillWithCircles(img, 60, 3)
+	x := rand.Intn(DotSize)
+	y := 0
+	color := image.NRGBAColor{0, 0, 0x80, 0xFF}
+	setRandomBrightness(&color, 180)
+	for _, n := range ns {
+		y = rand.Intn(DotSize*4)
+		drawNumber(img, numbers[n], x, y, color)
+		x += DotSize * NumberWidth + rand.Intn(SkewFactor)+3 
+	}
+	f, err := os.Create("captcha.png")
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+	png.Encode(f, img)
+}
+
+func main() {
+	rand.Seed(time.Seconds())
+	n := make([]byte, 6)
+	if _, err := io.ReadFull(crand.Reader, n); err != nil {
+		panic(err)
+	}
+	for i := range n {
+		n[i] %= 10
+	}
+	drawNumbersToImage(n)
+}
+