mirror of
https://github.com/la5nta/pat
synced 2026-08-13 17:46:54 -04:00
87 lines
2.2 KiB
Go
87 lines
2.2 KiB
Go
package app
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import (
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"bytes"
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"image"
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"image/jpeg" // jpeg decoding (and encoding)
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_ "image/png" // png decoding
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"io"
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"log"
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"mime"
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"path"
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"path/filepath"
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"strings"
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"github.com/la5nta/wl2k-go/fbb"
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_ "golang.org/x/image/bmp" // bmp decoding
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"golang.org/x/image/draw"
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)
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func AddAttachment(msg *fbb.Message, filename string, contentType string, r io.Reader) error {
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p, err := io.ReadAll(r)
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if err != nil {
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return err
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}
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if ok, mediaType := isConvertableImageMediaType(filename, contentType); ok {
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log.Printf("Auto converting '%s' [%s]...", filename, mediaType)
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if converted, err := convertImage(p); err != nil {
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log.Printf("Error converting image: %s", err)
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} else if len(converted) >= len(p) {
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log.Printf("Convertion did not reduce file size, using original '%s'.", filename)
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} else {
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log.Printf("Done converting '%s'.", filename)
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ext := filepath.Ext(filename)
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filename = filename[:len(filename)-len(ext)] + ".jpg"
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p = converted
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}
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}
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msg.AddFile(fbb.NewFile(filename, p))
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return nil
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}
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func isConvertableImageMediaType(filename, contentType string) (convertable bool, mediaType string) {
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if contentType != "" {
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mediaType, _, _ = mime.ParseMediaType(contentType)
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}
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if mediaType == "" {
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mediaType = mime.TypeByExtension(path.Ext(filename))
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}
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switch mediaType {
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case "image/svg+xml":
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// This is a text file
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return false, mediaType
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default:
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return strings.HasPrefix(mediaType, "image/"), mediaType
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}
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}
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func convertImage(orig []byte) ([]byte, error) {
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img, _, err := image.Decode(bytes.NewReader(orig))
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if err != nil {
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return nil, err
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}
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// Scale to a maximum width of 600px
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if img.Bounds().Dx() > 600 {
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img = resize(img, 600)
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}
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// Re-encode as low quality jpeg
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var buf bytes.Buffer
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if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 40}); err != nil {
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return orig, err
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}
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if buf.Len() >= len(orig) {
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return orig, nil
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}
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return buf.Bytes(), nil
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}
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func resize(img image.Image, newWidth int) image.Image {
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bounds := img.Bounds()
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height := bounds.Dy() * newWidth / bounds.Dx()
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dst := image.NewRGBA(image.Rect(0, 0, newWidth, height))
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draw.NearestNeighbor.Scale(dst, dst.Bounds(), img, bounds, draw.Src, nil)
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return dst
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}
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