github.com/insionng/yougam@v0.0.0-20170714101924-2bc18d833463/libraries/captcha/captcha.go

package captcha

import (
	"bytes"
	crand "crypto/rand"
	"image"
	"image/color"
	"image/png"
	"io"
	"math"
	"math/rand"
	"time"
)

const (
	fontWidth  = 11
	fontHeight = 18
	blackChar  = 1

	// Standard width and height of a captcha image.
	stdWidth  = 240
	stdHeight = 80

	// Maximum absolute skew factor of a single digit.
	maxSkew = 0.7

	// Number of background circles.
	circleCount = 20
)

var font = [][]byte{
	{ // 0
		0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0,
		0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0,
		1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1,
		0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0,
		0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0,
	},
	{ // 1
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0,
		0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0,
		0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
		0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	},
	{ // 2
		0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0,
		0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0,
		0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	},
	{ // 3
		0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0,
		0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0,
		0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,
		1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0,
	},
	{ // 4
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0,
		0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0,
		0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0,
		1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
	},
	{ // 5
		0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 0,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0,
	},
	{ // 6
		0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0,
		0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0,
		0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0,
		1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0,
		1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0,
		1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1,
		0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0,
		0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0,
	},
	{ // 7
		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
		1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
		0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0,
		0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0,
		0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0,
		0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0,
		0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0,
		0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0,
	},
	{ // 8
		0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0,
		0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0,
		0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0,
		0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0,
		0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0,
		1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
		0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0,
	},
	{ // 9
		0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
		0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0,
		1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1,
		0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1,
		0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1,
		0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0,
		0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0,
		0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0,
		0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
	},
}

type Image struct {
	*image.Paletted
	numWidth  int //a digit Width
	numHeight int //a digit Height
	dotSize   int
}

func init() {
	rand.Seed(int64(time.Second))
}

// randIntn returns a pseudorandom non-negative int in range [0, n).
func randIntn(n int) int {
	return rand.Intn(n)
}

// rnd returns a random number in range [from, to].
func randInt(from, to int) int {
	return rand.Intn(to+1-from) + from
}

// randFloat returns a pseudorandom float64 in range [from, to].
func randFloat(from, to float64) float64 {
	return (to-from)*rand.Float64() + from
}

func randomPalette() color.Palette {
	p := make([]color.Color, circleCount+1)
	// Transparent color.
	p[0] = color.RGBA{0xFF, 0xFF, 0xFF, 0x00}
	// Primary color.
	prim := color.RGBA{
		uint8(randIntn(129)),
		uint8(randIntn(129)),
		uint8(randIntn(129)),
		0xFF,
	}
	p[1] = prim
	// Circle colors.
	for i := 2; i <= circleCount; i++ {
		p[i] = randomBrightness(prim, 255)
	}
	return p
}

// NewImage returns a new captcha image of the given width and height with the
// given digits, where each digit must be in range 0-9.
func NewImage(digits []byte, width, height int) *Image {
	m := new(Image)
	m.Paletted = image.NewPaletted(image.Rect(0, 0, width, height), randomPalette())
	m.calculateSizes(width, height, len(digits))
	// Randomly position captcha inside the image.
	maxx := width - (m.numWidth+m.dotSize)*len(digits) - m.dotSize
	maxy := height - m.numHeight - m.dotSize*2
	var border int
	if width > height {
		border = height / 5
	} else {
		border = width / 5
	}
	x := randInt(border, maxx-border)
	y := randInt(border, maxy-border)
	// Draw digits.
	for _, n := range digits {
		m.drawDigit(font[n], x, y)
		x += m.numWidth + m.dotSize
	}
	// Draw strike-through line.
	m.strikeThrough()
	// Apply wave distortion.
	m.distort(randFloat(5, 10), randFloat(100, 200))
	// Fill image with random circles.
	m.fillWithCircles(circleCount, m.dotSize)
	return m
}

// encodedPNG encodes an image to PNG and returns
// the result as a byte slice.
func (m *Image) encodedPNG() []byte {
	var buf bytes.Buffer
	if err := png.Encode(&buf, m.Paletted); err != nil {
		panic(err.Error())
	}
	return buf.Bytes()
}

// WriteTo writes captcha image in PNG format into the given writer.
func (m *Image) WriteTo(w io.Writer) (int64, error) {
	n, err := w.Write(m.encodedPNG())
	return int64(n), err
}

func (m *Image) calculateSizes(width, height, ncount int) {
	// Goal: fit all digits inside the image.
	var border int
	if width > height {
		border = height / 4
	} else {
		border = width / 4
	}
	// Convert everything to floats for calculations.
	w := float64(width - border*2)
	h := float64(height - border*2)
	// fw takes into account 1-dot spacing between digits.
	fw := float64(fontWidth + 1)
	fh := float64(fontHeight)
	nc := float64(ncount)
	// Calculate the width of a single digit taking into account only the
	// width of the image.
	nw := w / nc
	// Calculate the height of a digit from this width.
	nh := nw * fh / fw
	// Digit too high?
	if nh > h {
		// Fit digits based on height.
		nh = h
		nw = fw / fh * nh
	}
	// Calculate dot size.
	m.dotSize = int(nh / fh)
	// Save everything, making the actual width smaller by 1 dot to account
	// for spacing between digits.
	m.numWidth = int(nw) - m.dotSize
	m.numHeight = int(nh)
}

func (m *Image) drawHorizLine(fromX, toX, y int, colorIdx uint8) {
	for x := fromX; x <= toX; x++ {
		m.SetColorIndex(x, y, colorIdx)
	}
}

func (m *Image) drawCircle(x, y, radius int, colorIdx uint8) {
	f := 1 - radius
	dfx := 1
	dfy := -2 * radius
	xo := 0
	yo := radius

	m.SetColorIndex(x, y+radius, colorIdx)
	m.SetColorIndex(x, y-radius, colorIdx)
	m.drawHorizLine(x-radius, x+radius, y, colorIdx)

	for xo < yo {
		if f >= 0 {
			yo--
			dfy += 2
			f += dfy
		}
		xo++
		dfx += 2
		f += dfx
		m.drawHorizLine(x-xo, x+xo, y+yo, colorIdx)
		m.drawHorizLine(x-xo, x+xo, y-yo, colorIdx)
		m.drawHorizLine(x-yo, x+yo, y+xo, colorIdx)
		m.drawHorizLine(x-yo, x+yo, y-xo, colorIdx)
	}
}

func (m *Image) fillWithCircles(n, maxradius int) {
	maxx := m.Bounds().Max.X
	maxy := m.Bounds().Max.Y
	for i := 0; i < n; i++ {
		colorIdx := uint8(randInt(1, circleCount-1))
		r := randInt(1, maxradius)
		m.drawCircle(randInt(r, maxx-r), randInt(r, maxy-r), r, colorIdx)
	}
}

func (m *Image) strikeThrough() {
	maxx := m.Bounds().Max.X
	maxy := m.Bounds().Max.Y
	y := randInt(maxy/3, maxy-maxy/3)
	amplitude := randFloat(5, 20)
	period := randFloat(80, 180)
	dx := 2.0 * math.Pi / period
	for x := 0; x < maxx; x++ {
		xo := amplitude * math.Cos(float64(y)*dx)
		yo := amplitude * math.Sin(float64(x)*dx)
		for yn := 0; yn < m.dotSize; yn++ {
			r := randInt(0, m.dotSize)
			m.drawCircle(x+int(xo), y+int(yo)+(yn*m.dotSize), r/2, 1)
		}
	}
}

func (m *Image) drawDigit(digit []byte, x, y int) {
	skf := randFloat(-maxSkew, maxSkew)
	xs := float64(x)
	r := m.dotSize / 2
	y += randInt(-r, r)
	for yo := 0; yo < fontHeight; yo++ {
		for xo := 0; xo < fontWidth; xo++ {
			if digit[yo*fontWidth+xo] != blackChar {
				continue
			}
			m.drawCircle(x+xo*m.dotSize, y+yo*m.dotSize, r, 1)
		}
		xs += skf
		x = int(xs)
	}
}

func (m *Image) distort(amplude float64, period float64) {
	w := m.Bounds().Max.X
	h := m.Bounds().Max.Y

	oldm := m.Paletted
	newm := image.NewPaletted(image.Rect(0, 0, w, h), oldm.Palette)

	dx := 2.0 * math.Pi / period
	for x := 0; x < w; x++ {
		for y := 0; y < h; y++ {
			xo := amplude * math.Sin(float64(y)*dx)
			yo := amplude * math.Cos(float64(x)*dx)
			newm.SetColorIndex(x, y, oldm.ColorIndexAt(x+int(xo), y+int(yo)))
		}
	}
	m.Paletted = newm
}

func randomBrightness(c color.RGBA, max uint8) color.RGBA {
	minc := min3(c.R, c.G, c.B)
	maxc := max3(c.R, c.G, c.B)
	if maxc > max {
		return c
	}
	n := randIntn(int(max-maxc)) - int(minc)
	return color.RGBA{
		uint8(int(c.R) + n),
		uint8(int(c.G) + n),
		uint8(int(c.B) + n),
		uint8(c.A),
	}
}

func min3(x, y, z uint8) (m uint8) {
	m = x
	if y < m {
		m = y
	}
	if z < m {
		m = z
	}
	return
}

func max3(x, y, z uint8) (m uint8) {
	m = x
	if y > m {
		m = y
	}
	if z > m {
		m = z
	}
	return
}

const (
	// Standard length of uniuri string to achive ~95 bits of entropy.
	StdLen = 16
	// Length of uniurl string to achive ~119 bits of entropy, closest
	// to what can be losslessly converted to UUIDv4 (122 bits).
	UUIDLen = 20
)

// Standard characters allowed in uniuri string.
var StdChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")

// New returns a new random string of the standard length, consisting of
// standard characters.
func New() string {
	return NewLenChars(StdLen, StdChars)
}

// NewLen returns a new random string of the provided length, consisting of
// standard characters.
func NewLen(length int) string {
	return NewLenChars(length, StdChars)
}

// NewLenChars returns a new random string of the provided length, consisting
// of the provided byte slice of allowed characters (maximum 256).
func NewLenChars(length int, chars []byte) string {
	b := make([]byte, length)
	r := make([]byte, length+(length/4)) // storage for random bytes.
	clen := byte(len(chars))
	maxrb := byte(256 - (256 % len(chars)))
	i := 0
	for {
		if _, err := io.ReadFull(crand.Reader, r); err != nil {
			panic("error reading from random source: " + err.Error())
		}
		for _, c := range r {
			if c >= maxrb {
				// Skip this number to avoid modulo bias.
				continue
			}
			b[i] = chars[c%clen]
			i++
			if i == length {
				return string(b)
			}
		}
	}
	panic("unreachable")
}

// func pic(w http.ResponseWriter, req *http.Request) {
// 	d := make([]byte, 4)
// 	s := NewLen(4)
// 	ss := ""
// 	d = []byte(s)
// 	for v := range d {
// 		d[v] %= 10
// 		ss += strconv.FormatInt(int64(d[v]), 32)
// 	}
// 	w.Header().Set("Content-Type", "image/png")
// 	NewImage(d, 100, 40).WriteTo(w)
// 	fmt.Println(ss)
// }

// func index(w http.ResponseWriter, req *http.Request) {
// 	str := "<meta charset=\"utf-8\"><h3>golang 图片验证码例子</h3><img border=\"1\" src=\"/pic\" alt=\"图片验证码\" onclick=\"this.src='/pic'\" />"
// 	w.Header().Set("Content-Type", "text/html")
// 	w.Write([]byte(str))
// }

// func main() {
// 	http.HandleFunc("/pic", pic)
// 	http.HandleFunc("/", index)
// 	s := &http.Server{
// 		Addr: 		 	":8080",
// 		ReadTimeout: 	30*time.Second,
// 		WriteTimeout: 	30*time.Second,
// 		MaxHeaderBytes: 1 << 20,
// 	}
// 	s.ListenAndServe()
// }