Better builtin avatar generator (#17707)

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 #14799
3. Fix a small padding error in the algorithm

19 files changed, 417 insertions, 376 deletions

diff --git a/build/codeformat/formatimports_test.go b/build/codeformat/formatimports_test.go
index d308353bda..3db90cad7b 100644
--- a/build/codeformat/formatimports_test.go
+++ b/build/codeformat/formatimports_test.go
@@ -50,7 +50,7 @@ import (
 	"bytes"
 	"fmt"
 	"image"
-	"image/color/palette"
+	"image/color"
 
 	_ "image/gif"  // for processing gif images
 	_ "image/jpeg" // for processing jpeg images
@@ -76,7 +76,7 @@ import (
 	"bytes"
 	"fmt"
 	"image"
-	"image/color/palette"
+	"image/color"
 
 	_ "image/gif"  // for processing gif images
 	_ "image/jpeg" // for processing jpeg images
diff --git a/go.mod b/go.mod
index ae37a8240b..a1146372ad 100644
--- a/go.mod
+++ b/go.mod
@@ -63,7 +63,6 @@ require (
 	github.com/hashicorp/go-version v1.3.1
 	github.com/hashicorp/golang-lru v0.5.4
 	github.com/huandu/xstrings v1.3.2
-	github.com/issue9/identicon v1.2.0
 	github.com/jaytaylor/html2text v0.0.0-20200412013138-3577fbdbcff7
 	github.com/json-iterator/go v1.1.11
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51
diff --git a/go.sum b/go.sum
index 58b21910cb..bdbf33eddc 100644
--- a/go.sum
+++ b/go.sum
@@ -661,10 +661,6 @@ github.com/imdario/mergo v0.3.12 h1:b6R2BslTbIEToALKP7LxUvijTsNI9TAe80pLWN2g/HU=
 github.com/imdario/mergo v0.3.12/go.mod h1:jmQim1M+e3UYxmgPu/WyfjB3N3VflVyUjjjwH0dnCYA=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
 github.com/influxdata/influxdb1-client v0.0.0-20191209144304-8bf82d3c094d/go.mod h1:qj24IKcXYK6Iy9ceXlo3Tc+vtHo9lIhSX5JddghvEPo=
-github.com/issue9/assert v1.4.1 h1:gUtOpMTeaE4JTe9kACma5foOHBvVt1p5XTFrULDwdXI=
-github.com/issue9/assert v1.4.1/go.mod h1:Yktk83hAVl1SPSYtd9kjhBizuiBIqUQyj+D5SE2yjVY=
-github.com/issue9/identicon v1.2.0 h1:ek+UcTTyMW/G0iNbLOAlrPC13eSzXTWhbJSs8PHhHGQ=
-github.com/issue9/identicon v1.2.0/go.mod h1:A9toNT0ky/1WP5iNFyDmrkNiYH6eX3HcN5V6uH0g0ec=
 github.com/jackc/chunkreader v1.0.0 h1:4s39bBR8ByfqH+DKm8rQA3E1LHZWB9XWcrz8fqaZbe0=
 github.com/jackc/chunkreader v1.0.0/go.mod h1:RT6O25fNZIuasFJRyZ4R/Y2BbhasbmZXF9QQ7T3kePo=
 github.com/jackc/chunkreader/v2 v2.0.0/go.mod h1:odVSm741yZoC3dpHEUXIqA9tQRhFrgOHwnPIn9lDKlk=
diff --git a/modules/avatar/avatar.go b/modules/avatar/avatar.go
index 5411a90796..6ca75ed90f 100644
--- a/modules/avatar/avatar.go
+++ b/modules/avatar/avatar.go
@@ -8,16 +8,15 @@ import (
 	"bytes"
 	"fmt"
 	"image"
-	"image/color/palette"
+	"image/color"
 
 	_ "image/gif"  // for processing gif images
 	_ "image/jpeg" // for processing jpeg images
 	_ "image/png"  // for processing png images
 
+	"code.gitea.io/gitea/modules/avatar/identicon"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/util"
 
-	"github.com/issue9/identicon"
 	"github.com/nfnt/resize"
 	"github.com/oliamb/cutter"
 )
@@ -28,20 +27,8 @@ const AvatarSize = 290
 // RandomImageSize generates and returns a random avatar image unique to input data
 // in custom size (height and width).
 func RandomImageSize(size int, data []byte) (image.Image, error) {
-	randExtent := len(palette.WebSafe) - 32
-	integer, err := util.RandomInt(int64(randExtent))
-	if err != nil {
-		return nil, fmt.Errorf("util.RandomInt: %v", err)
-	}
-	colorIndex := int(integer)
-	backColorIndex := colorIndex - 1
-	if backColorIndex < 0 {
-		backColorIndex = randExtent - 1
-	}
-
-	// Define size, background, and forecolor
-	imgMaker, err := identicon.New(size,
-		palette.WebSafe[backColorIndex], palette.WebSafe[colorIndex:colorIndex+32]...)
+	// we use white as background, and use dark colors to draw blocks
+	imgMaker, err := identicon.New(size, color.White, identicon.DarkColors...)
 	if err != nil {
 		return nil, fmt.Errorf("identicon.New: %v", err)
 	}
diff --git a/vendor/github.com/issue9/identicon/block.go b/modules/avatar/identicon/block.go
index 887ffea388..b8eed5895e 100644
--- a/vendor/github.com/issue9/identicon/block.go
+++ b/modules/avatar/identicon/block.go
@@ -1,25 +1,26 @@
-// SPDX-License-Identifier: MIT
+// 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)
 
 package identicon
 
 import "image"
 
 var (
-	// 可以出现在中间的方块，一般为了美观，都是对称图像。
+	// the blocks can appear in center, these blocks can be more beautiful
 	centerBlocks = []blockFunc{b0, b1, b2, b3, b19, b26, b27}
 
-	// 所有方块
+	// all blocks
 	blocks = []blockFunc{b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16, b17, b18, b19, b20, b21, b22, b23, b24, b25, b26, b27}
 )
 
-// 所有 block 函数的类型
 type blockFunc func(img *image.Paletted, x, y, size int, angle int)
 
-// 将多边形 points 旋转 angle 个角度，然后输出到 img 上，起点为 x,y 坐标
-//
-// points 中的坐标是基于左上角是原点的坐标系。
+// draw a polygon by points, and the polygon is rotated by angle.
 func drawBlock(img *image.Paletted, x, y, size int, angle int, points []int) {
-	if angle > 0 { // 0 角度不需要转换
+	if angle != 0 {
 		m := size / 2
 		rotate(points, m, m, angle)
 	}
@@ -33,7 +34,7 @@ func drawBlock(img *image.Paletted, x, y, size int, angle int, points []int) {
 	}
 }
 
-// 全空白
+// blank
 //
 //  --------
 //  |      |
@@ -42,7 +43,7 @@ func drawBlock(img *image.Paletted, x, y, size int, angle int, points []int) {
 //  --------
 func b0(img *image.Paletted, x, y, size int, angle int) {}
 
-// 全填充正方形
+// full-filled
 //
 //  --------
 //  |######|
@@ -57,7 +58,7 @@ func b1(img *image.Paletted, x, y, size int, angle int) {
 	}
 }
 
-// 中间小方块
+// a small block
 //  ----------
 //  |        |
 //  |  ####  |
@@ -66,8 +67,8 @@ func b1(img *image.Paletted, x, y, size int, angle int) {
 //  ----------
 func b2(img *image.Paletted, x, y, size int, angle int) {
 	l := size / 4
-	x = x + l
-	y = y + l
+	x += l
+	y += l
 
 	for i := x; i < x+2*l; i++ {
 		for j := y; j < y+2*l; j++ {
@@ -76,7 +77,7 @@ func b2(img *image.Paletted, x, y, size int, angle int) {
 	}
 }
 
-// 菱形
+// diamond
 //
 //  ---------
 //  |   #   |
@@ -133,7 +134,7 @@ func b5(img *image.Paletted, x, y, size int, angle int) {
 	})
 }
 
-// b6 矩形
+// b6
 //
 //  --------
 //  |###   |
@@ -151,7 +152,7 @@ func b6(img *image.Paletted, x, y, size int, angle int) {
 	})
 }
 
-// b7 斜放的锥形
+// b7 italic cone
 //
 //  ---------
 //  | #     |
@@ -170,7 +171,7 @@ func b7(img *image.Paletted, x, y, size int, angle int) {
 	})
 }
 
-// b8 三个堆叠的三角形
+// b8 three small triangles
 //
 //  -----------
 //  |    #    |
@@ -184,7 +185,7 @@ func b8(img *image.Paletted, x, y, size int, angle int) {
 	m := size / 2
 	mm := m / 2
 
-	// 顶部三角形
+	// top
 	drawBlock(img, x, y, size, angle, []int{
 		m, 0,
 		3 * mm, m,
@@ -192,7 +193,7 @@ func b8(img *image.Paletted, x, y, size int, angle int) {
 		m, 0,
 	})
 
-	// 底下左边
+	// bottom left
 	drawBlock(img, x, y, size, angle, []int{
 		mm, m,
 		m, size,
@@ -200,7 +201,7 @@ func b8(img *image.Paletted, x, y, size int, angle int) {
 		mm, m,
 	})
 
-	// 底下右边
+	// bottom right
 	drawBlock(img, x, y, size, angle, []int{
 		3 * mm, m,
 		size, size,
@@ -209,7 +210,7 @@ func b8(img *image.Paletted, x, y, size int, angle int) {
 	})
 }
 
-// b9 斜靠的三角形
+// b9 italic triangle
 //
 //  ---------
 //  |#      |
@@ -257,7 +258,7 @@ func b10(img *image.Paletted, x, y, size int, angle int) {
 	})
 }
 
-// b11 左上角1/4大小的方块
+// b11
 //
 //  ----------
 //  |####    |
diff --git a/modules/avatar/identicon/colors.go b/modules/avatar/identicon/colors.go
new file mode 100644
index 0000000000..a8d7090369
--- /dev/null
+++ b/modules/avatar/identicon/colors.go
@@ -0,0 +1,135 @@
+// 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.
+
+package identicon
+
+import "image/color"
+
+// DarkColors are dark colors for avatar blocks, they come from image/color/palette.WebSafe, and light colors (0xff) are removed
+var DarkColors = []color.Color{
+	color.RGBA{0x00, 0x00, 0x33, 0xff},
+	color.RGBA{0x00, 0x00, 0x66, 0xff},
+	color.RGBA{0x00, 0x00, 0x99, 0xff},
+	color.RGBA{0x00, 0x00, 0xcc, 0xff},
+	color.RGBA{0x00, 0x33, 0x00, 0xff},
+	color.RGBA{0x00, 0x33, 0x33, 0xff},
+	color.RGBA{0x00, 0x33, 0x66, 0xff},
+	color.RGBA{0x00, 0x33, 0x99, 0xff},
+	color.RGBA{0x00, 0x33, 0xcc, 0xff},
+	color.RGBA{0x00, 0x66, 0x00, 0xff},
+	color.RGBA{0x00, 0x66, 0x33, 0xff},
+	color.RGBA{0x00, 0x66, 0x66, 0xff},
+	color.RGBA{0x00, 0x66, 0x99, 0xff},
+	color.RGBA{0x00, 0x66, 0xcc, 0xff},
+	color.RGBA{0x00, 0x99, 0x00, 0xff},
+	color.RGBA{0x00, 0x99, 0x33, 0xff},
+	color.RGBA{0x00, 0x99, 0x66, 0xff},
+	color.RGBA{0x00, 0x99, 0x99, 0xff},
+	color.RGBA{0x00, 0x99, 0xcc, 0xff},
+	color.RGBA{0x00, 0xcc, 0x00, 0xff},
+	color.RGBA{0x00, 0xcc, 0x33, 0xff},
+	color.RGBA{0x00, 0xcc, 0x66, 0xff},
+	color.RGBA{0x00, 0xcc, 0x99, 0xff},
+	color.RGBA{0x00, 0xcc, 0xcc, 0xff},
+	color.RGBA{0x33, 0x00, 0x00, 0xff},
+	color.RGBA{0x33, 0x00, 0x33, 0xff},
+	color.RGBA{0x33, 0x00, 0x66, 0xff},
+	color.RGBA{0x33, 0x00, 0x99, 0xff},
+	color.RGBA{0x33, 0x00, 0xcc, 0xff},
+	color.RGBA{0x33, 0x33, 0x00, 0xff},
+	color.RGBA{0x33, 0x33, 0x33, 0xff},
+	color.RGBA{0x33, 0x33, 0x66, 0xff},
+	color.RGBA{0x33, 0x33, 0x99, 0xff},
+	color.RGBA{0x33, 0x33, 0xcc, 0xff},
+	color.RGBA{0x33, 0x66, 0x00, 0xff},
+	color.RGBA{0x33, 0x66, 0x33, 0xff},
+	color.RGBA{0x33, 0x66, 0x66, 0xff},
+	color.RGBA{0x33, 0x66, 0x99, 0xff},
+	color.RGBA{0x33, 0x66, 0xcc, 0xff},
+	color.RGBA{0x33, 0x99, 0x00, 0xff},
+	color.RGBA{0x33, 0x99, 0x33, 0xff},
+	color.RGBA{0x33, 0x99, 0x66, 0xff},
+	color.RGBA{0x33, 0x99, 0x99, 0xff},
+	color.RGBA{0x33, 0x99, 0xcc, 0xff},
+	color.RGBA{0x33, 0xcc, 0x00, 0xff},
+	color.RGBA{0x33, 0xcc, 0x33, 0xff},
+	color.RGBA{0x33, 0xcc, 0x66, 0xff},
+	color.RGBA{0x33, 0xcc, 0x99, 0xff},
+	color.RGBA{0x33, 0xcc, 0xcc, 0xff},
+	color.RGBA{0x66, 0x00, 0x00, 0xff},
+	color.RGBA{0x66, 0x00, 0x33, 0xff},
+	color.RGBA{0x66, 0x00, 0x66, 0xff},
+	color.RGBA{0x66, 0x00, 0x99, 0xff},
+	color.RGBA{0x66, 0x00, 0xcc, 0xff},
+	color.RGBA{0x66, 0x33, 0x00, 0xff},
+	color.RGBA{0x66, 0x33, 0x33, 0xff},
+	color.RGBA{0x66, 0x33, 0x66, 0xff},
+	color.RGBA{0x66, 0x33, 0x99, 0xff},
+	color.RGBA{0x66, 0x33, 0xcc, 0xff},
+	color.RGBA{0x66, 0x66, 0x00, 0xff},
+	color.RGBA{0x66, 0x66, 0x33, 0xff},
+	color.RGBA{0x66, 0x66, 0x66, 0xff},
+	color.RGBA{0x66, 0x66, 0x99, 0xff},
+	color.RGBA{0x66, 0x66, 0xcc, 0xff},
+	color.RGBA{0x66, 0x99, 0x00, 0xff},
+	color.RGBA{0x66, 0x99, 0x33, 0xff},
+	color.RGBA{0x66, 0x99, 0x66, 0xff},
+	color.RGBA{0x66, 0x99, 0x99, 0xff},
+	color.RGBA{0x66, 0x99, 0xcc, 0xff},
+	color.RGBA{0x66, 0xcc, 0x00, 0xff},
+	color.RGBA{0x66, 0xcc, 0x33, 0xff},
+	color.RGBA{0x66, 0xcc, 0x66, 0xff},
+	color.RGBA{0x66, 0xcc, 0x99, 0xff},
+	color.RGBA{0x66, 0xcc, 0xcc, 0xff},
+	color.RGBA{0x99, 0x00, 0x00, 0xff},
+	color.RGBA{0x99, 0x00, 0x33, 0xff},
+	color.RGBA{0x99, 0x00, 0x66, 0xff},
+	color.RGBA{0x99, 0x00, 0x99, 0xff},
+	color.RGBA{0x99, 0x00, 0xcc, 0xff},
+	color.RGBA{0x99, 0x33, 0x00, 0xff},
+	color.RGBA{0x99, 0x33, 0x33, 0xff},
+	color.RGBA{0x99, 0x33, 0x66, 0xff},
+	color.RGBA{0x99, 0x33, 0x99, 0xff},
+	color.RGBA{0x99, 0x33, 0xcc, 0xff},
+	color.RGBA{0x99, 0x66, 0x00, 0xff},
+	color.RGBA{0x99, 0x66, 0x33, 0xff},
+	color.RGBA{0x99, 0x66, 0x66, 0xff},
+	color.RGBA{0x99, 0x66, 0x99, 0xff},
+	color.RGBA{0x99, 0x66, 0xcc, 0xff},
+	color.RGBA{0x99, 0x99, 0x00, 0xff},
+	color.RGBA{0x99, 0x99, 0x33, 0xff},
+	color.RGBA{0x99, 0x99, 0x66, 0xff},
+	color.RGBA{0x99, 0x99, 0x99, 0xff},
+	color.RGBA{0x99, 0x99, 0xcc, 0xff},
+	color.RGBA{0x99, 0xcc, 0x00, 0xff},
+	color.RGBA{0x99, 0xcc, 0x33, 0xff},
+	color.RGBA{0x99, 0xcc, 0x66, 0xff},
+	color.RGBA{0x99, 0xcc, 0x99, 0xff},
+	color.RGBA{0x99, 0xcc, 0xcc, 0xff},
+	color.RGBA{0xcc, 0x00, 0x00, 0xff},
+	color.RGBA{0xcc, 0x00, 0x33, 0xff},
+	color.RGBA{0xcc, 0x00, 0x66, 0xff},
+	color.RGBA{0xcc, 0x00, 0x99, 0xff},
+	color.RGBA{0xcc, 0x00, 0xcc, 0xff},
+	color.RGBA{0xcc, 0x33, 0x00, 0xff},
+	color.RGBA{0xcc, 0x33, 0x33, 0xff},
+	color.RGBA{0xcc, 0x33, 0x66, 0xff},
+	color.RGBA{0xcc, 0x33, 0x99, 0xff},
+	color.RGBA{0xcc, 0x33, 0xcc, 0xff},
+	color.RGBA{0xcc, 0x66, 0x00, 0xff},
+	color.RGBA{0xcc, 0x66, 0x33, 0xff},
+	color.RGBA{0xcc, 0x66, 0x66, 0xff},
+	color.RGBA{0xcc, 0x66, 0x99, 0xff},
+	color.RGBA{0xcc, 0x66, 0xcc, 0xff},
+	color.RGBA{0xcc, 0x99, 0x00, 0xff},
+	color.RGBA{0xcc, 0x99, 0x33, 0xff},
+	color.RGBA{0xcc, 0x99, 0x66, 0xff},
+	color.RGBA{0xcc, 0x99, 0x99, 0xff},
+	color.RGBA{0xcc, 0x99, 0xcc, 0xff},
+	color.RGBA{0xcc, 0xcc, 0x00, 0xff},
+	color.RGBA{0xcc, 0xcc, 0x33, 0xff},
+	color.RGBA{0xcc, 0xcc, 0x66, 0xff},
+	color.RGBA{0xcc, 0xcc, 0x99, 0xff},
+	color.RGBA{0xcc, 0xcc, 0xcc, 0xff},
+}
diff --git a/modules/avatar/identicon/identicon.go b/modules/avatar/identicon/identicon.go
new file mode 100644
index 0000000000..8589c59289
--- /dev/null
+++ b/modules/avatar/identicon/identicon.go
@@ -0,0 +1,141 @@
+// 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))
+		}
+	}
+}
diff --git a/modules/avatar/identicon/identicon_test.go b/modules/avatar/identicon/identicon_test.go
new file mode 100644
index 0000000000..ab54183a46
--- /dev/null
+++ b/modules/avatar/identicon/identicon_test.go
@@ -0,0 +1,42 @@
+// 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.
+
+//go:build test_avatar_identicon
+//  +build test_avatar_identicon
+
+package identicon
+
+import (
+	"image/color"
+	"image/png"
+	"os"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGenerate(t *testing.T) {
+	dir, _ := os.Getwd()
+	dir = dir + "/testdata"
+	if st, err := os.Stat(dir); err != nil || !st.IsDir() {
+		t.Errorf("can not save generated images to %s", dir)
+	}
+
+	backColor := color.White
+	imgMaker, err := New(64, backColor, DarkColors...)
+	assert.NoError(t, err)
+	for i := 0; i < 100; i++ {
+		s := strconv.Itoa(i)
+		img := imgMaker.Make([]byte(s))
+
+		f, err := os.Create(dir + "/" + s + ".png")
+		if !assert.NoError(t, err) {
+			continue
+		}
+		defer f.Close()
+		err = png.Encode(f, img)
+		assert.NoError(t, err)
+	}
+}
diff --git a/modules/avatar/identicon/polygon.go b/modules/avatar/identicon/polygon.go
new file mode 100644
index 0000000000..02890737da
--- /dev/null
+++ b/modules/avatar/identicon/polygon.go
@@ -0,0 +1,69 @@
+// 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)
+
+package identicon
+
+var (
+	// cos(0),cos(90),cos(180),cos(270)
+	cos = []int{1, 0, -1, 0}
+
+	// sin(0),sin(90),sin(180),sin(270)
+	sin = []int{0, 1, 0, -1}
+)
+
+// rotate the points by center point (x,y)
+// angle: [0,1,2,3] means [0，90，180，270] degree
+func rotate(points []int, x, y int, angle int) {
+	// the angle is only used internally, and it has been guaranteed to be 0/1/2/3, so we do not check it again
+	for i := 0; i < len(points); i += 2 {
+		px, py := points[i]-x, points[i+1]-y
+		points[i] = px*cos[angle] - py*sin[angle] + x
+		points[i+1] = px*sin[angle] + py*cos[angle] + y
+	}
+}
+
+// check whether the point is inside the polygon (defined by the points)
+// the first and the last point must be the same
+func pointInPolygon(x, y int, polygonPoints []int) bool {
+	if len(polygonPoints) < 8 { // a valid polygon must have more than 2 points
+		return false
+	}
+
+	// reference: nonzero winding rule, https://en.wikipedia.org/wiki/Nonzero-rule
+	// split the plane into two by the check point horizontally:
+	//   y>0，includes (x>0 && y==0)
+	//   y<0，includes (x<0 && y==0)
+	//
+	// then scan every point in the polygon.
+	//
+	// if current point and previous point are in different planes (eg: curY>0 && prevY<0),
+	// check the clock-direction from previous point to current point (use check point as origin).
+	// if the direction is clockwise, then r++, otherwise then r--
+	// finally, if 2==abs(r), then the check point is inside the polygon
+
+	r := 0
+	prevX, prevY := polygonPoints[0], polygonPoints[1]
+	prev := (prevY > y) || ((prevX > x) && (prevY == y))
+	for i := 2; i < len(polygonPoints); i += 2 {
+		currX, currY := polygonPoints[i], polygonPoints[i+1]
+		curr := (currY > y) || ((currX > x) && (currY == y))
+
+		if curr == prev {
+			prevX, prevY = currX, currY
+			continue
+		}
+
+		if mul := (prevX-x)*(currY-y) - (currX-x)*(prevY-y); mul >= 0 {
+			r++
+		} else { // mul < 0
+			r--
+		}
+		prevX, prevY = currX, currY
+		prev = curr
+	}
+
+	return r == 2 || r == -2
+}
diff --git a/modules/avatar/identicon/testdata/.gitignore b/modules/avatar/identicon/testdata/.gitignore
new file mode 100644
index 0000000000..72e8ffc0db
--- /dev/null
+++ b/modules/avatar/identicon/testdata/.gitignore
@@ -0,0 +1 @@
+*
diff --git a/vendor/github.com/issue9/identicon/.gitignore b/vendor/github.com/issue9/identicon/.gitignore
deleted file mode 100644
index 3e7884f1fa..0000000000
--- a/vendor/github.com/issue9/identicon/.gitignore
+++ /dev/null
@@ -1,23 +0,0 @@
-# Compiled Object files, Static and Dynamic libs (Shared Objects)
-*.o
-*.a
-*.so
-
-# Folders
-_obj
-_test
-
-*.exe
-*.test
-*.prof
-
-#vim
-*.swp
-
-#osx
-.DS_Store
-
-/testdata/*.png
-
-.idea
-.vscode
\ No newline at end of file
diff --git a/vendor/github.com/issue9/identicon/LICENSE b/vendor/github.com/issue9/identicon/LICENSE
deleted file mode 100644
index e92d1181e5..0000000000
--- a/vendor/github.com/issue9/identicon/LICENSE
+++ /dev/null
@@ -1,22 +0,0 @@
-The MIT License (MIT)
-
-Copyright (c) 2015 caixw
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
-
diff --git a/vendor/github.com/issue9/identicon/README.md b/vendor/github.com/issue9/identicon/README.md
deleted file mode 100644
index 2331e953c6..0000000000
--- a/vendor/github.com/issue9/identicon/README.md
+++ /dev/null
@@ -1,38 +0,0 @@
-# identicon
-
-[![Go](https://github.com/issue9/identicon/actions/workflows/go.yml/badge.svg)](https://github.com/issue9/identicon/actions/workflows/go.yml)
-[![codecov](https://codecov.io/gh/issue9/identicon/branch/master/graph/badge.svg)](https://codecov.io/gh/issue9/identicon)
-[![PkgGoDev](https://pkg.go.dev/badge/github.com/issue9/identicon)](https://pkg.go.dev/github.com/issue9/identicon)
-![Go version](https://img.shields.io/github/go-mod/go-version/issue9/identicon)
-![License](https://img.shields.io/github/license/issue9/identicon)
-
-根据用户的 IP 、邮箱名等任意数据为用户产生漂亮的随机头像。
-
-![screenshot.1](https://raw.github.com/issue9/identicon/master/screenshot/1.png)
-![screenshot.4](https://raw.github.com/issue9/identicon/master/screenshot/4.png)
-![screenshot.5](https://raw.github.com/issue9/identicon/master/screenshot/5.png)
-![screenshot.6](https://raw.github.com/issue9/identicon/master/screenshot/6.png)
-![screenshot.7](https://raw.github.com/issue9/identicon/master/screenshot/7.png)
-
-```go
-// 根据用户访问的IP，为其生成一张头像
-img, _ := identicon.Make(128, color.NRGBA{},color.NRGBA{}, []byte("192.168.1.1"))
-fi, _ := os.Create("/tmp/u1.png")
-png.Encode(fi, img)
-fi.Close()
-
-// 或者
-ii, _ := identicon.New(128, color.NRGBA{}, color.NRGBA{}, color.NRGBA{}, color.NRGBA{})
-img := ii.Make([]byte("192.168.1.1"))
-img = ii.Make([]byte("192.168.1.2"))
-```
-
-## 安装
-
-```shell
-go get github.com/issue9/identicon
-```
-
-## 版权
-
-本项目采用 [MIT](https://opensource.org/licenses/MIT) 开源授权许可证，完整的授权说明可在 [LICENSE](LICENSE) 文件中找到。
diff --git a/vendor/github.com/issue9/identicon/doc.go b/vendor/github.com/issue9/identicon/doc.go
deleted file mode 100644
index 3a7129829a..0000000000
--- a/vendor/github.com/issue9/identicon/doc.go
+++ /dev/null
@@ -1,35 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-// Package identicon 一个基于 hash 值生成随机图像的包
-//
-// identicon 并没有统一的标准，一般用于在用户注册时，
-// 取用户的邮箱或是访问 IP 等数据(也可以是其它任何数据)，
-// 进行 hash 运算，之后根据 hash 数据，产生一张图像，
-// 这样即可以为用户产生一张独特的头像，又不会泄漏用户的隐藏。
-//
-// 在 identicon 中，把图像分成以下九个部分:
-//  -------------
-//  | 1 | 2 | 3 |
-//  -------------
-//  | 4 | 5 | 6 |
-//  -------------
-//  | 7 | 8 | 9 |
-//  -------------
-// 其中 1、3、9、7 为不同角度(依次增加 90 度)的同一张图片，
-// 2、6、8、4 也是如此，这样可以保持图像是对称的，比较美观。
-// 5 则单独使用一张图片。
-//
-//  // 根据用户访问的 IP ，为其生成一张头像
-//  img, _ := identicon.Make(128, color.NRGBA{},color.NRGBA{}, []byte("192.168.1.1"))
-//  fi, _ := os.Create("/tmp/u1.png")
-//  png.Encode(fi, img)
-//  fi.Close()
-//
-//  // 或者
-//  ii, _ := identicon.New(128, color.NRGBA{}, color.NRGBA{}, color.NRGBA{})
-//  img := ii.Make([]byte("192.168.1.1"))
-//  img = ii.Make([]byte("192.168.1.2"))
-//
-// NOTE: go test 会在当前目录的 testdata 文件夹下产生大量的随机图片。
-// 要运行测试，必须保证该文件夹是存在的，且有相应的写入权限。
-package identicon
diff --git a/vendor/github.com/issue9/identicon/go.mod b/vendor/github.com/issue9/identicon/go.mod
deleted file mode 100644
index 3c0f2a918f..0000000000
--- a/vendor/github.com/issue9/identicon/go.mod
+++ /dev/null
@@ -1,5 +0,0 @@
-module github.com/issue9/identicon
-
-require github.com/issue9/assert v1.4.1
-
-go 1.13
diff --git a/vendor/github.com/issue9/identicon/go.sum b/vendor/github.com/issue9/identicon/go.sum
deleted file mode 100644
index e03cdc34cc..0000000000
--- a/vendor/github.com/issue9/identicon/go.sum
+++ /dev/null
@@ -1,2 +0,0 @@
-github.com/issue9/assert v1.4.1 h1:gUtOpMTeaE4JTe9kACma5foOHBvVt1p5XTFrULDwdXI=
-github.com/issue9/assert v1.4.1/go.mod h1:Yktk83hAVl1SPSYtd9kjhBizuiBIqUQyj+D5SE2yjVY=
diff --git a/vendor/github.com/issue9/identicon/identicon.go b/vendor/github.com/issue9/identicon/identicon.go
deleted file mode 100644
index 1c34d2f060..0000000000
--- a/vendor/github.com/issue9/identicon/identicon.go
+++ /dev/null
@@ -1,137 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-package identicon
-
-import (
-	"crypto/md5"
-	"fmt"
-	"image"
-	"image/color"
-	"math/rand"
-)
-
-const (
-	minSize       = 16 // 图片的最小尺寸
-	maxForeColors = 32 // 在New()函数中可以指定的最大颜色数量
-)
-
-// Identicon 用于产生统一尺寸的头像
-//
-// 可以根据用户提供的数据，经过一定的算法，自动产生相应的图案和颜色。
-type Identicon struct {
-	foreColors []color.Color
-	backColor  color.Color
-	size       int
-	rect       image.Rectangle
-}
-
-// New 声明一个 Identicon 实例
-//
-// size 表示整个头像的大小；
-// back 表示前景色；
-// fore 表示所有可能的前景色，会为每个图像随机挑选一个作为其前景色。
-func New(size int, back color.Color, fore ...color.Color) (*Identicon, error) {
-	if len(fore) == 0 || len(fore) > maxForeColors {
-		return nil, fmt.Errorf("前景色数量必须介于[1]~[%d]之间，当前为[%d]", maxForeColors, len(fore))
-	}
-
-	if size < minSize {
-		return nil, fmt.Errorf("参数 size 的值(%d)不能小于 %d", size, minSize)
-	}
-
-	return &Identicon{
-		foreColors: fore,
-		backColor:  back,
-		size:       size,
-
-		// 画布坐标从0开始，其长度应该是 size-1
-		rect: image.Rect(0, 0, size, size),
-	}, nil
-}
-
-// Make 根据 data 数据产生一张唯一性的头像图片
-func (i *Identicon) Make(data []byte) image.Image {
-	h := md5.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
-	color := int(sum[11]+sum[12]+sum[15]) % len(i.foreColors)
-
-	return i.render(c, b1, b2, b1Angle, b2Angle, color)
-}
-
-// Rand 随机生成图案
-func (i *Identicon) Rand(r *rand.Rand) image.Image {
-	b1 := r.Intn(len(blocks))
-	b2 := r.Intn(len(blocks))
-	c := r.Intn(len(centerBlocks))
-	b1Angle := r.Intn(4)
-	b2Angle := r.Intn(4)
-	color := r.Intn(len(i.foreColors))
-
-	return i.render(c, b1, b2, b1Angle, b2Angle, color)
-}
-
-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
-}
-
-// Make 根据 data 数据产生一张唯一性的头像图片
-//
-// size 头像的大小。
-// back, fore头像的背景和前景色。
-func Make(size int, back, fore color.Color, data []byte) (image.Image, error) {
-	i, err := New(size, back, fore)
-	if err != nil {
-		return nil, err
-	}
-	return i.Make(data), nil
-}
-
-// 将九个方格都填上内容。
-// p 为画板；
-// c 为中间方格的填充函数；
-// b1、b2 为边上 8 格的填充函数；
-// b1Angle 和 b2Angle 为 b1、b2 的起始旋转角度。
-func drawBlocks(p *image.Paletted, size int, c, b1, b2 blockFunc, b1Angle, b2Angle int) {
-	incr := func(a int) int {
-		if a >= 3 {
-			a = 0
-		} else {
-			a++
-		}
-		return a
-	}
-
-	padding := (size % 6) / 2 // 不能除尽的，边上留白。
-
-	blockSize := size / 3
-	twoBlockSize := 2 * blockSize
-
-	c(p, blockSize+padding, blockSize+padding, blockSize, 0)
-
-	b1(p, 0+padding, 0+padding, blockSize, b1Angle)
-	b2(p, blockSize+padding, 0+padding, blockSize, b2Angle)
-
-	b1Angle = incr(b1Angle)
-	b2Angle = incr(b2Angle)
-	b1(p, twoBlockSize+padding, 0+padding, blockSize, b1Angle)
-	b2(p, twoBlockSize+padding, blockSize+padding, blockSize, b2Angle)
-
-	b1Angle = incr(b1Angle)
-	b2Angle = incr(b2Angle)
-	b1(p, twoBlockSize+padding, twoBlockSize+padding, blockSize, b1Angle)
-	b2(p, blockSize+padding, twoBlockSize+padding, blockSize, b2Angle)
-
-	b1Angle = incr(b1Angle)
-	b2Angle = incr(b2Angle)
-	b1(p, 0+padding, twoBlockSize+padding, blockSize, b1Angle)
-	b2(p, 0+padding, blockSize+padding, blockSize, b2Angle)
-}
diff --git a/vendor/github.com/issue9/identicon/polygon.go b/vendor/github.com/issue9/identicon/polygon.go
deleted file mode 100644
index eedb98c834..0000000000
--- a/vendor/github.com/issue9/identicon/polygon.go
+++ /dev/null
@@ -1,65 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-package identicon
-
-var (
-	// 4 个元素分别表示 cos(0),cos(90),cos(180),cos(270)
-	cos = []int{1, 0, -1, 0}
-
-	// 4 个元素分别表示 sin(0),sin(90),sin(180),sin(270)
-	sin = []int{0, 1, 0, -1}
-)
-
-// 将 points 中的所有点，以 x,y 为原点旋转 angle 个角度。
-// angle 取值只能是 [0,1,2,3]，分别表示 [0，90，180，270]
-func rotate(points []int, x, y int, angle int) {
-	if angle < 0 || angle > 3 {
-		panic("rotate:参数angle必须0,1,2,3三值之一")
-	}
-
-	for i := 0; i < len(points); i += 2 {
-		px, py := points[i]-x, points[i+1]-y
-		points[i] = px*cos[angle] - py*sin[angle] + x
-		points[i+1] = px*sin[angle] + py*cos[angle] + y
-	}
-}
-
-// 判断某个点是否在多边形之内，不包含构成多边形的线和点
-// x,y 需要判断的点坐标
-// points 组成多边形的所顶点，每两个元素表示一点顶点，其中最后一个顶点必须与第一个顶点相同。
-func pointInPolygon(x, y int, points []int) bool {
-	if len(points) < 8 { // 只有2个以上的点，才能组成闭合多边形
-		return false
-	}
-
-	// 大致算法如下：
-	// 把整个平面以给定的测试点为原点分两部分:
-	// - y>0，包含(x>0 && y==0)
-	// - y<0，包含(x<0 && y==0)
-	// 依次扫描每一个点，当该点与前一个点处于不同部分时（即一个在 y>0 区，一个在 y<0 区），
-	// 则判断从前一点到当前点是顺时针还是逆时针（以给定的测试点为原点），如果是顺时针 r++，否则 r--。
-	// 结果为：2==abs(r)。
-
-	r := 0
-	x1, y1 := points[0], points[1]
-	prev := (y1 > y) || ((x1 > x) && (y1 == y))
-	for i := 2; i < len(points); i += 2 {
-		x2, y2 := points[i], points[i+1]
-		curr := (y2 > y) || ((x2 > x) && (y2 == y))
-
-		if curr == prev {
-			x1, y1 = x2, y2
-			continue
-		}
-
-		if mul := (x1-x)*(y2-y) - (x2-x)*(y1-y); mul >= 0 {
-			r++
-		} else if mul < 0 {
-			r--
-		}
-		x1, y1 = x2, y2
-		prev = curr
-	}
-
-	return r == 2 || r == -2
-}
diff --git a/vendor/modules.txt b/vendor/modules.txt
index b34531f259..77a624c4b6 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -507,9 +507,6 @@ github.com/hashicorp/hcl/json/token
 github.com/huandu/xstrings
 # github.com/imdario/mergo v0.3.12
 github.com/imdario/mergo
-# github.com/issue9/identicon v1.2.0
-## explicit
-github.com/issue9/identicon
 # github.com/jaytaylor/html2text v0.0.0-20200412013138-3577fbdbcff7
 ## explicit
 github.com/jaytaylor/html2text