82 lines
2 KiB
Go
82 lines
2 KiB
Go
package main
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import (
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"bytes"
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"context"
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"encoding/base64"
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"fmt"
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"image"
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"image/png"
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_ "image/gif"
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_ "image/jpeg"
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_ "github.com/biessek/golang-ico"
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_ "golang.org/x/image/webp"
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)
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// convertIconToBase64PNG downloads an icon from S3, converts it to PNG, and returns base64-encoded data.
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func convertIconToBase64PNG(ctx context.Context, s3Key string, iconsBucket string) (encoded string, width, height int, err error) {
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data, err := s3Download(ctx, iconsBucket, s3Key)
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if err != nil {
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return "", 0, 0, fmt.Errorf("s3 download: %w", err)
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}
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// Check for SVG (can't decode to raster without external deps)
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if isSVG(data) {
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return "", 0, 0, fmt.Errorf("svg not supported")
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}
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// image.Decode handles PNG, GIF, JPEG, WebP, BMP, and ICO (via registered decoders)
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img, _, err := image.Decode(bytes.NewReader(data))
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if err != nil {
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return "", 0, 0, fmt.Errorf("decode: %w", err)
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}
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// Downscale icons >128px to 32x32 to keep bundle sizes reasonable
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bounds := img.Bounds()
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w, h := bounds.Dx(), bounds.Dy()
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if w > 128 || h > 128 {
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img = resizeNearestNeighbor(img, 32, 32)
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w, h = 32, 32
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}
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// Re-encode as PNG
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var pngBuf bytes.Buffer
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if err := png.Encode(&pngBuf, img); err != nil {
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return "", 0, 0, fmt.Errorf("png encode: %w", err)
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}
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encoded = base64.StdEncoding.EncodeToString(pngBuf.Bytes())
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return encoded, w, h, nil
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}
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// resizeNearestNeighbor does a simple nearest-neighbor resize.
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func resizeNearestNeighbor(src image.Image, dstW, dstH int) image.Image {
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srcBounds := src.Bounds()
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srcW := srcBounds.Dx()
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srcH := srcBounds.Dy()
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dst := image.NewRGBA(image.Rect(0, 0, dstW, dstH))
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for y := 0; y < dstH; y++ {
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srcY := srcBounds.Min.Y + y*srcH/dstH
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for x := 0; x < dstW; x++ {
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srcX := srcBounds.Min.X + x*srcW/dstW
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dst.Set(x, y, src.At(srcX, srcY))
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}
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}
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return dst
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}
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func isSVG(data []byte) bool {
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if len(data) < 5 {
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return false
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}
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header := data[:min(256, len(data))]
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return bytes.Contains(header, []byte("<svg")) || bytes.Contains(header, []byte("<?xml"))
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}
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func min(a, b int) int {
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if a < b {
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return a
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}
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return b
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}
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