1 files changed, 139 insertions, 0 deletions
diff --git a/modules/avatar/avatar.go b/modules/avatar/avatar.go
new file mode 100644
index 0000000..106215e
--- /dev/null
+++ b/modules/avatar/avatar.go
@@ -0,0 +1,139 @@
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package avatar
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"image"
+	"image/color"
+	"image/png"
+
+	_ "image/gif"  // for processing gif images
+	_ "image/jpeg" // for processing jpeg images
+
+	"code.gitea.io/gitea/modules/avatar/identicon"
+	"code.gitea.io/gitea/modules/setting"
+
+	"golang.org/x/image/draw"
+
+	_ "golang.org/x/image/webp" // for processing webp images
+)
+
+// DefaultAvatarSize is the target CSS pixel size for avatar generation. It is
+// multiplied by setting.Avatar.RenderedSizeFactor and the resulting size is the
+// usual size of avatar image saved on server, unless the original file is smaller
+// than the size after resizing.
+const DefaultAvatarSize = 256
+
+// 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) {
+	// 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: %w", err)
+	}
+	return imgMaker.Make(data), nil
+}
+
+// RandomImage generates and returns a random avatar image unique to input data
+// in default size (height and width).
+func RandomImage(data []byte) (image.Image, error) {
+	return RandomImageSize(DefaultAvatarSize*setting.Avatar.RenderedSizeFactor, data)
+}
+
+// processAvatarImage process the avatar image data, crop and resize it if necessary.
+// the returned data could be the original image if no processing is needed.
+func processAvatarImage(data []byte, maxOriginSize int64) ([]byte, error) {
+	imgCfg, imgType, err := image.DecodeConfig(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("image.DecodeConfig: %w", err)
+	}
+
+	// for safety, only accept known types explicitly
+	if imgType != "png" && imgType != "jpeg" && imgType != "gif" && imgType != "webp" {
+		return nil, errors.New("unsupported avatar image type")
+	}
+
+	// do not process image which is too large, it would consume too much memory
+	if imgCfg.Width > setting.Avatar.MaxWidth {
+		return nil, fmt.Errorf("image width is too large: %d > %d", imgCfg.Width, setting.Avatar.MaxWidth)
+	}
+	if imgCfg.Height > setting.Avatar.MaxHeight {
+		return nil, fmt.Errorf("image height is too large: %d > %d", imgCfg.Height, setting.Avatar.MaxHeight)
+	}
+
+	// If the origin is small enough, just use it, then APNG could be supported,
+	// otherwise, if the image is processed later, APNG loses animation.
+	// And one more thing, webp is not fully supported, for animated webp, image.DecodeConfig works but Decode fails.
+	// So for animated webp, if the uploaded file is smaller than maxOriginSize, it will be used, if it's larger, there will be an error.
+	if len(data) < int(maxOriginSize) {
+		return data, nil
+	}
+
+	img, _, err := image.Decode(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("image.Decode: %w", err)
+	}
+
+	// try to crop and resize the origin image if necessary
+	img = cropSquare(img)
+
+	targetSize := DefaultAvatarSize * setting.Avatar.RenderedSizeFactor
+	img = scale(img, targetSize, targetSize, draw.BiLinear)
+
+	// try to encode the cropped/resized image to png
+	bs := bytes.Buffer{}
+	if err = png.Encode(&bs, img); err != nil {
+		return nil, err
+	}
+	resized := bs.Bytes()
+
+	// usually the png compression is not good enough, use the original image (no cropping/resizing) if the origin is smaller
+	if len(data) <= len(resized) {
+		return data, nil
+	}
+
+	return resized, nil
+}
+
+// ProcessAvatarImage process the avatar image data, crop and resize it if necessary.
+// the returned data could be the original image if no processing is needed.
+func ProcessAvatarImage(data []byte) ([]byte, error) {
+	return processAvatarImage(data, setting.Avatar.MaxOriginSize)
+}
+
+// scale resizes the image to width x height using the given scaler.
+func scale(src image.Image, width, height int, scale draw.Scaler) image.Image {
+	rect := image.Rect(0, 0, width, height)
+	dst := image.NewRGBA(rect)
+	scale.Scale(dst, rect, src, src.Bounds(), draw.Over, nil)
+	return dst
+}
+
+// cropSquare crops the largest square image from the center of the image.
+// If the image is already square, it is returned unchanged.
+func cropSquare(src image.Image) image.Image {
+	bounds := src.Bounds()
+	if bounds.Dx() == bounds.Dy() {
+		return src
+	}
+
+	var rect image.Rectangle
+	if bounds.Dx() > bounds.Dy() {
+		// width > height
+		size := bounds.Dy()
+		rect = image.Rect((bounds.Dx()-size)/2, 0, (bounds.Dx()+size)/2, size)
+	} else {
+		// width < height
+		size := bounds.Dx()
+		rect = image.Rect(0, (bounds.Dy()-size)/2, size, (bounds.Dy()+size)/2)
+	}
+
+	dst := image.NewRGBA(rect)
+	draw.Draw(dst, rect, src, rect.Min, draw.Src)
+	return dst
+}