bench-forgejo/modules/avatar/identicon/identicon.go
wxiaoguang a8fd76557b
Better builtin avatar generator ()
This PR fixes the builtin avatar generator.

1. The random background color makes some images very dirty. So now we only use white background for avatars.
2. We use left-right mirror avatars to satisfy 
3. Fix a small padding error in the algorithm
2021-11-20 01:10:41 +08:00

141 lines
3.8 KiB
Go

// Copyright 2021 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
// Copied and modified from https://github.com/issue9/identicon/ (MIT License)
// Generate pseudo-random avatars by IP, E-mail, etc.
package identicon
import (
"crypto/sha256"
"fmt"
"image"
"image/color"
)
const minImageSize = 16
// Identicon is used to generate pseudo-random avatars
type Identicon struct {
foreColors []color.Color
backColor color.Color
size int
rect image.Rectangle
}
// New returns an Identicon struct with the correct settings
// size image size
// back background color
// fore all possible foreground colors. only one foreground color will be picked randomly for one image
func New(size int, back color.Color, fore ...color.Color) (*Identicon, error) {
if len(fore) == 0 {
return nil, fmt.Errorf("foreground is not set")
}
if size < minImageSize {
return nil, fmt.Errorf("size %d is smaller than min size %d", size, minImageSize)
}
return &Identicon{
foreColors: fore,
backColor: back,
size: size,
rect: image.Rect(0, 0, size, size),
}, nil
}
// Make generates an avatar by data
func (i *Identicon) Make(data []byte) image.Image {
h := sha256.New()
h.Write(data)
sum := h.Sum(nil)
b1 := int(sum[0]+sum[1]+sum[2]) % len(blocks)
b2 := int(sum[3]+sum[4]+sum[5]) % len(blocks)
c := int(sum[6]+sum[7]+sum[8]) % len(centerBlocks)
b1Angle := int(sum[9]+sum[10]) % 4
b2Angle := int(sum[11]+sum[12]) % 4
foreColor := int(sum[11]+sum[12]+sum[15]) % len(i.foreColors)
return i.render(c, b1, b2, b1Angle, b2Angle, foreColor)
}
func (i *Identicon) render(c, b1, b2, b1Angle, b2Angle, foreColor int) image.Image {
p := image.NewPaletted(i.rect, []color.Color{i.backColor, i.foreColors[foreColor]})
drawBlocks(p, i.size, centerBlocks[c], blocks[b1], blocks[b2], b1Angle, b2Angle)
return p
}
/*
# Algorithm
Origin: An image is splitted into 9 areas
```
-------------
| 1 | 2 | 3 |
-------------
| 4 | 5 | 6 |
-------------
| 7 | 8 | 9 |
-------------
```
Area 1/3/9/7 use a 90-degree rotating pattern.
Area 1/3/9/7 use another 90-degree rotating pattern.
Area 5 uses a random patter.
The Patched Fix: make the image left-right mirrored to get rid of something like "swastika"
*/
// draw blocks to the paletted
// c: the block drawer for the center block
// b1,b2: the block drawers for other blocks (around the center block)
// b1Angle,b2Angle: the angle for the rotation of b1/b2
func drawBlocks(p *image.Paletted, size int, c, b1, b2 blockFunc, b1Angle, b2Angle int) {
nextAngle := func(a int) int {
return (a + 1) % 4
}
padding := (size % 3) / 2 // in cased the size can not be aligned by 3 blocks.
blockSize := size / 3
twoBlockSize := 2 * blockSize
// center
c(p, blockSize+padding, blockSize+padding, blockSize, 0)
// left top (1)
b1(p, 0+padding, 0+padding, blockSize, b1Angle)
// center top (2)
b2(p, blockSize+padding, 0+padding, blockSize, b2Angle)
b1Angle = nextAngle(b1Angle)
b2Angle = nextAngle(b2Angle)
// right top (3)
// b1(p, twoBlockSize+padding, 0+padding, blockSize, b1Angle)
// right middle (6)
// b2(p, twoBlockSize+padding, blockSize+padding, blockSize, b2Angle)
b1Angle = nextAngle(b1Angle)
b2Angle = nextAngle(b2Angle)
// right bottom (9)
// b1(p, twoBlockSize+padding, twoBlockSize+padding, blockSize, b1Angle)
// center bottom (8)
b2(p, blockSize+padding, twoBlockSize+padding, blockSize, b2Angle)
b1Angle = nextAngle(b1Angle)
b2Angle = nextAngle(b2Angle)
// lef bottom (7)
b1(p, 0+padding, twoBlockSize+padding, blockSize, b1Angle)
// left middle (4)
b2(p, 0+padding, blockSize+padding, blockSize, b2Angle)
// then we make it left-right mirror, so we didn't draw 3/6/9 before
for x := 0; x < size/2; x++ {
for y := 0; y < size; y++ {
p.SetColorIndex(size-x, y, p.ColorIndexAt(x, y))
}
}
}