88 lines
2.2 KiB
Go
88 lines
2.2 KiB
Go
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package pmocover
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import (
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"bytes"
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"image"
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"image/draw"
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"os"
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"path/filepath"
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"strconv"
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"github.com/chai2010/webp"
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xdraw "golang.org/x/image/draw"
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)
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// encodeWebP convertit une image.Image en WebP avec compression sans perte.
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func encodeWebP(img image.Image) ([]byte, error) {
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var buf bytes.Buffer
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if err := webp.Encode(&buf, img, &webp.Options{Lossless: true}); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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// ensureSquare génère une image carrée paddée transparente
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func ensureSquare(img image.Image, size int) image.Image {
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dst := image.NewRGBA(image.Rect(0, 0, size, size))
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draw.Draw(dst, dst.Bounds(), &image.Uniform{C: image.Transparent}, image.Point{}, draw.Src)
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srcBounds := img.Bounds()
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srcW, srcH := srcBounds.Dx(), srcBounds.Dy()
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var scale float64
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if srcW > srcH {
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scale = float64(size) / float64(srcW)
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} else {
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scale = float64(size) / float64(srcH)
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}
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newW, newH := int(float64(srcW)*scale), int(float64(srcH)*scale)
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// redimensionnement avec Catmull-Rom
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tmp := image.NewRGBA(image.Rect(0, 0, newW, newH))
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xdraw.CatmullRom.Scale(tmp, tmp.Bounds(), img, srcBounds, xdraw.Over, nil)
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// centrer l'image redimensionnée dans le carré
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offset := image.Pt((size-newW)/2, (size-newH)/2)
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draw.Draw(dst, tmp.Bounds().Add(offset), tmp, image.Point{}, draw.Over)
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return dst
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}
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// generateVariant génère une version carrée en WebP pour une taille donnée.
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// Si le fichier existe déjà, il est renvoyé directement.
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func (c *Cache) generateVariant(pk string, size int) ([]byte, error) {
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variantPath := filepath.Join(c.dir, pk+"."+strconv.Itoa(size)+".webp")
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// si le variant existe déjà, le renvoyer
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if data, err := os.ReadFile(variantPath); err == nil {
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return data, nil
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}
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// lire l'image originale
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origPath := filepath.Join(c.dir, pk+".orig.webp")
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data, err := os.ReadFile(origPath)
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if err != nil {
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return nil, err
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}
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img, _, err := image.Decode(bytes.NewReader(data))
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if err != nil {
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return nil, err
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}
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// générer une image carrée
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sq := ensureSquare(img, size)
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// encoder en WebP
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buf, err := encodeWebP(sq)
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if err != nil {
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return nil, err
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}
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// sauvegarder le variant
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if err := os.WriteFile(variantPath, buf, 0o644); err != nil {
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return nil, err
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}
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return buf, nil
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}
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