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gogs/modules/captcha/image.go

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// Copyright 2014 The Gogs Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package captcha
import (
"bytes"
"image"
"image/color"
"image/png"
"io"
"math"
)
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
numHeight int
dotSize int
}
var prng = &siprng{}
// randIntn returns a pseudorandom non-negative int in range [0, n).
func randIntn(n int) int {
return prng.Intn(n)
}
// randInt returns a pseudorandom int in range [from, to].
func randInt(from, to int) int {
return prng.Intn(to+1-from) + from
}
// randFloat returns a pseudorandom float64 in range [from, to].
func randFloat(from, to float64) float64 {
return (to-from)*prng.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
}