Refactored image captcha ready, and documented.

image.go

@@ -9,7 +9,10 @@ import (
 )
 
 const (
-	maxSkew = 3
+	maxSkew = 2
+	// Standard width and height for captcha image
+	StdWidth  = 300
+	StdHeight = 80
 )
 
 type CaptchaImage struct {
@@ -17,37 +20,11 @@ type CaptchaImage struct {
 	primaryColor image.NRGBAColor
 	numberWidth  int
 	numberHeight int
-	dotSize    int
-}
-
-func (img *CaptchaImage) calculateSizes(width, height, ncount int) {
-	// Goal: fit all numbers into the image.
-	// Convert everything to floats for calculations.
-	w := float64(width)
-	h := float64(height)
-	// fontWidth includes 1-dot spacing between numbers
-	fw := float64(fontWidth) + 1
-	fh := float64(fontHeight)
-	nc := float64(ncount)
-	// Calculate width of a sigle number if we only take into
-	// account the width
-	nw := w / nc
-	// Calculate the number height from this width
-	nh := nw * fh / fw
-	// Number height too large?
-	if nh > h {
-		// Fit numbers based on height
-		nh = h
-		nw = fw/fh * nh
-	}
-	// Calculate dot size
-	img.dotSize = int(nh / fh)
-	// Save everything, making actual width smaller by 1 dot,
-	// to account for spacing between numbers
-	img.numberWidth = int(nw)
-	img.numberHeight = int(nh) - img.dotSize
+	dotSize      int
 }
 
+// NewImage returns a new captcha image of the given width and height with the
+// given slice of numbers, where each number is 0-9.
 func NewImage(numbers []byte, width, height int) *CaptchaImage {
 	img := new(CaptchaImage)
 	img.NRGBA = image.NewNRGBA(width, height)
@@ -55,36 +32,70 @@ func NewImage(numbers []byte, width, height int) *CaptchaImage {
 	// We need some space, so calculate border
 	var border int
 	if width > height {
-		border = height/5
+		border = height / 5
 	} else {
-		border = width/5
+		border = width / 5
 	}
-	bwidth := width-border*2
-	bheight := height-border*2
+	bwidth := width - border*2
+	bheight := height - border*2
 	img.calculateSizes(bwidth, bheight, len(numbers))
-	// Center numbers in image
-	x := width/2 - (img.numberWidth*len(numbers))/2 - img.dotSize
-	y := height/2 - img.numberHeight/2 + img.dotSize/2
+	// Background 
+	img.fillWithCircles(10, img.dotSize)
+	maxx := width - (img.numberWidth+img.dotSize)*len(numbers) - img.dotSize
+	maxy := height - img.numberHeight - img.dotSize*2
+	x := rnd(img.dotSize*2, maxx)
+	y := rnd(img.dotSize*2, maxy)
 	setRandomBrightness(&img.primaryColor, 180)
 	for _, n := range numbers {
-		//y = rand.Intn(dotSize * 4)
 		img.drawNumber(font[n], x, y)
 		x += img.numberWidth + img.dotSize
 	}
-	//img.strikeThrough(img.primaryColor)
+	img.strikeThrough()
 	return img
 }
 
+// NewRandomImage generates random numbers and returns a new captcha image of
+// the given width and height with those numbers printed on it, and the numbers
+// themselves.
 func NewRandomImage(width, height int) (img *CaptchaImage, numbers []byte) {
 	numbers = randomNumbers()
 	img = NewImage(numbers, width, height)
 	return
 }
 
+// PNGEncode writes captcha image in PNG format into the given writer.
 func (img *CaptchaImage) PNGEncode(w io.Writer) os.Error {
 	return png.Encode(w, img)
 }
 
+func (img *CaptchaImage) calculateSizes(width, height, ncount int) {
+	// Goal: fit all numbers into the image.
+	// Convert everything to floats for calculations.
+	w := float64(width)
+	h := float64(height)
+	// fontWidth includes 1-dot spacing between numbers
+	fw := float64(fontWidth) + 1
+	fh := float64(fontHeight)
+	nc := float64(ncount)
+	// Calculate width of a sigle number if we only take into
+	// account the width
+	nw := w / nc
+	// Calculate the number height from this width
+	nh := nw * fh / fw
+	// Number height too large?
+	if nh > h {
+		// Fit numbers based on height
+		nh = h
+		nw = fw / fh * nh
+	}
+	// Calculate dot size
+	img.dotSize = int(nh / fh)
+	// Save everything, making actual width smaller by 1 dot,
+	// to account for spacing between numbers
+	img.numberWidth = int(nw)
+	img.numberHeight = int(nh) - img.dotSize
+}
+
 func (img *CaptchaImage) drawHorizLine(color image.Color, fromX, toX, y int) {
 	for x := fromX; x <= toX; x++ {
 		img.Set(x, y, color)
@@ -118,7 +129,6 @@ func (img *CaptchaImage) drawCircle(color image.Color, x, y, radius int) {
 	}
 }
 
-
 func min3(x, y, z uint8) (o uint8) {
 	o = x
 	if y < o {
@@ -157,42 +167,38 @@ func rnd(from, to int) int {
 	return rand.Intn(to+1-from) + from
 }
 
-func (img *CaptchaImage) fillWithCircles(color image.NRGBAColor, n, maxradius int) {
+func (img *CaptchaImage) fillWithCircles(n, maxradius int) {
+	color := img.primaryColor
 	maxx := img.Bounds().Max.X
 	maxy := img.Bounds().Max.Y
 	for i := 0; i < n; i++ {
 		setRandomBrightness(&color, 255)
 		r := rnd(1, maxradius)
-		img.drawCircle(color, rnd(r, maxx), rnd(r, maxy), r)
+		img.drawCircle(color, rnd(r, maxx-r), rnd(r, maxy-r), r)
 	}
 }
 
-// func (img *CaptchaImage) strikeThrough(color image.Color) {
-// 	r := 0
-// 	maxx := img.Bounds().Max.X
-// 	maxy := img.Bounds().Max.Y
-// 	y := rnd(maxy/3, maxy-maxy/3)
-// 	for x := 0; x < maxx; x += r {
-// 		r = rnd(1, dotSize/2-1)
-// 		y += rnd(-2, 2)
-// 		if y <= 0 || y >= maxy {
-// 			y = rnd(maxy/3, maxy-maxy/3)
-// 		}
-// 		img.drawCircle(color, x, y, r)
-// 	}
-// }
+func (img *CaptchaImage) strikeThrough() {
+	r := 0
+	maxx := img.Bounds().Max.X
+	maxy := img.Bounds().Max.Y
+	y := rnd(maxy/3, maxy-maxy/3)
+	for x := 0; x < maxx; x += r {
+		r = rnd(1, img.dotSize/2-1)
+		y += rnd(-img.dotSize/2, img.dotSize/2)
+		if y <= 0 || y >= maxy {
+			y = rnd(maxy/3, maxy-maxy/3)
+		}
+		img.drawCircle(img.primaryColor, x, y, r)
+	}
+}
 
 func (img *CaptchaImage) drawNumber(number []byte, x, y int) {
-	//skf := rand.Intn(maxSkew) - maxSkew/2
-	//if skf < 0 {
-	//	x -= skf * numberHeight
-	//}
-	//d := img.numberWidth / fontWidth // number height is ignored
-	//println(img.numberWidth)
-	minr := img.dotSize/2 // minumum radius
-	maxr := img.dotSize // maximum radius
-	// x += srad
-	// y += srad
+	skf := rand.Float64() * float64(rnd(-maxSkew, maxSkew))
+	xs := float64(x)
+	minr := img.dotSize / 2               // minumum radius
+	maxr := img.dotSize/2 + img.dotSize/4 // maximum radius
+	y += rnd(-minr, minr)
 	for yy := 0; yy < fontHeight; yy++ {
 		for xx := 0; xx < fontWidth; xx++ {
 			if number[yy*fontWidth+xx] != 1 {
@@ -200,10 +206,11 @@ func (img *CaptchaImage) drawNumber(number []byte, x, y int) {
 			}
 			// introduce random variations
 			or := rnd(minr, maxr)
-			ox := x + (xx * maxr) //+ rnd(0, or/2)
-			oy := y + (yy * maxr) //+ rnd(0, or/2)
+			ox := x + (xx * img.dotSize) + rnd(0, or/2)
+			oy := y + (yy * img.dotSize) + rnd(0, or/2)
 			img.drawCircle(img.primaryColor, ox, oy, or)
 		}
-		//x += skf
+		xs += skf
+		x = int(xs)
 	}
 }