package
main
import (
crand "crypto/rand"
"fmt"
"image"
"image/color"
"image/png"
"io"
"math/rand"
"net/http"
"strconv"
"time"
)
const (
stdWidth = 100
stdHeight = 40
maxSkew = 2
)
const (
fontWidth = 5
fontHeight = 8
blackChar = 1
)
var font = [][]byte{
{ // 0
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,
},
{ // 1
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,
},
{ // 2
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,
},
{ // 3
1, 1, 1, 1, 0,
0, 0, 0, 0, 1,
0, 0, 0, 1, 0,
0, 1, 1, 1, 0,
0, 0, 0, 1, 0,
0, 0, 0, 0, 1,
0, 0, 0, 0, 1,
1, 1, 1, 1, 0,
},
{ // 4
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,
},
{ // 5
1, 1, 1, 1, 1,
1, 0, 0, 0, 0,
1, 0, 0, 0, 0,
1, 1, 1, 1, 0,
0, 0, 0, 0, 1,
0, 0, 0, 0, 1,
0, 0, 0, 0, 1,
1, 1, 1, 1, 0,
},
{ // 6
0, 0, 1, 1, 1,
0, 1, 0, 0, 0,
1, 0, 0, 0, 0,
1, 1, 1, 1, 0,
1, 0, 0, 0, 1,
1, 0, 0, 0, 1,
1, 0, 0, 0, 1,
0, 1, 1, 1, 0,
},
{ // 7
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,
},
{ // 8
0, 1, 1, 1, 0,
1, 0, 0, 0, 1,
1, 0, 0, 0, 1,
0, 1, 1, 1, 0,
1, 0, 0, 0, 1,
1, 0, 0, 0, 1,
1, 0, 0, 0, 1,
0, 1, 1, 1, 0,
},
{ // 9
0, 1, 1, 1, 0,
1, 0, 0, 0, 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,
},
}
type Image struct {
*image.NRGBA
color *color.NRGBA
width int //a digit width
height int //a digit height
dotsize int
}
func init() {
rand.Seed(int64(time.Second))
}
func NewImage(digits []byte, width, height int) *Image {
img := new(Image)
r := image.Rect(img.width, img.height, stdWidth, stdHeight)
img.NRGBA = image.NewNRGBA(r)
img.color = &color.NRGBA{
uint8(rand.Intn(129)),
uint8(rand.Intn(129)),
uint8(rand.Intn(129)),
0xFF,
}
// Draw background (10 random circles of random brightness)
img.calculateSizes(width, height, len(digits))
img.fillWithCircles(10, img.dotsize)
maxx := width - (img.width+img.dotsize)*len(digits) - img.dotsize
maxy := height - img.height - img.dotsize*2
x := rnd(img.dotsize*2, maxx)
y := rnd(img.dotsize*2, maxy)
// Draw digits.
for _, n := range digits {
img.drawDigit(font[n], x, y)
x += img.width + img.dotsize
}
// Draw strike-through line.
img.strikeThrough()
return img
}
func (img *Image) WriteTo(w io.Writer) (int64, error) {
return 0, png.Encode(w, img)
}
func (img *Image) calculateSizes(width, height, ncount int) {
// Goal: fit all digits inside the image.
var border int
if width > height {
border = height / 5
} else {
border = width / 5
}
// Convert everything to floats for calculations.
w := float64(width - border*2) //268
h := float64(height - border*2) //48
// fw takes into account 1-dot spacing between digits.
fw := float64(fontWidth) + 1 //6
fh := float64(fontHeight) //8
nc := float64(ncount) //7
// Calculate the width of a single digit taking into account only the
// width of the image.
nw := w / nc //38
// Calculate the height of a digit from this width.
nh := nw * fh / fw //51
// Digit too high?
if nh > h {
// Fit digits based on height.
nh = h //nh = 44
nw = fw / fh * nh
}
// Calculate dot size.
img.dotsize = int(nh / fh)
// Save everything, making the actual width smaller by 1 dot to account
// for spacing between digits.
img.width = int(nw)
img.height = int(nh) - img.dotsize
}
func (img *Image) fillWithCircles(n, maxradius int) {
color := img.color
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-r), rnd(r, maxy-r), r)
}
}
func (img *Image) drawHorizLine(color color.Color, fromX, toX, y int) {
for x := fromX; x <= toX; x++ {
img.Set(x, y, color)
}
}
func (img *Image) drawCircle(color color.Color, x, y, radius int) {
f := 1 - radius
dfx := 1
dfy := -2 * radius
xx := 0
yy := radius
img.Set(x, y+radius, color)
img.Set(x, y-radius, color)
img.drawHorizLine(color, x-radius, x+radius, y)
for xx < yy {
if f >= 0 {
yy--
dfy += 2
f += dfy
}
xx++
dfx += 2
f += dfx
img.drawHorizLine(color, x-xx, x+xx, y+yy)
img.drawHorizLine(color, x-xx, x+xx, y-yy)
img.drawHorizLine(color, x-yy, x+yy, y+xx)
img.drawHorizLine(color, x-yy, x+yy, y-xx)
}
}
func (img *Image) 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/3)
y += rnd(-img.dotsize/2, img.dotsize/2)
if y <= 0 || y >= maxy {
y = rnd(maxy/3, maxy-maxy/3)
}
img.drawCircle(img.color, x, y, r)
}
}
func (img *Image) drawDigit(digit []byte, x, y int) {
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 digit[yy*fontWidth+xx] != blackChar {
continue
}
// Introduce random variations.
or := rnd(minr, maxr)
ox := x + (xx * img.dotsize) + rnd(0, or/2)
oy := y + (yy * img.dotsize) + rnd(0, or/2)
img.drawCircle(img.color, ox, oy, or)
}
xs += skf
x = int(xs)
}
}
func setRandomBrightness(c *color.NRGBA, 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 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
}
// rnd returns a random number in range [from, to].
func rnd(from, to int) int {
//println(to+1-from)
return rand.Intn(to+1-from) + from
}
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()
}
有疑问加站长微信联系（非本文作者）
