Initial QSfera import

Server/services/thumbnails/pkg/thumbnail/generator.go

@@ -0,0 +1,99 @@
+package thumbnail
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"image/gif"
+	"strings"
+
+	"github.com/kovidgoyal/imaging"
+	"github.com/qsfera/server/services/thumbnails/pkg/errors"
+)
+
+// Generator generates a web friendly file version.
+type Generator interface {
+	Generate(size image.Rectangle, img any) (any, error)
+	Dimensions(img any) (image.Rectangle, error)
+	ProcessorID() string
+}
+
+// GifGenerator is used to create a web friendly version of the provided gif image.
+type GifGenerator struct {
+	processor Processor
+}
+
+func NewGifGenerator(filetype, process string) (GifGenerator, error) {
+	processor, err := ProcessorFor(process, filetype)
+	if err != nil {
+		return GifGenerator{}, err
+	}
+	return GifGenerator{processor: processor}, nil
+
+}
+
+// ProcessorID returns the processor identification.
+func (g GifGenerator) ProcessorID() string {
+	return g.processor.ID()
+}
+
+// Generate generates a alternative gif version.
+func (g GifGenerator) Generate(size image.Rectangle, img any) (any, error) {
+	// Code inspired by https://github.com/willnorris/gifresize/blob/db93a7e1dcb1c279f7eeb99cc6d90b9e2e23e871/gifresize.go
+
+	m, ok := img.(*gif.GIF)
+	if !ok {
+		return nil, errors.ErrInvalidType
+	}
+	// Create a new RGBA image to hold the incremental frames.
+	srcX, srcY := m.Config.Width, m.Config.Height
+	b := image.Rect(0, 0, srcX, srcY)
+	tmp := image.NewRGBA(b)
+
+	for i, frame := range m.Image {
+		bounds := frame.Bounds()
+		prev := tmp
+		draw.Draw(tmp, bounds, frame, bounds.Min, draw.Over)
+		processed := g.processor.Process(tmp, size.Dx(), size.Dy(), imaging.Lanczos)
+		m.Image[i] = g.imageToPaletted(processed, frame.Palette)
+
+		switch m.Disposal[i] {
+		case gif.DisposalBackground:
+			tmp = image.NewRGBA(b)
+		case gif.DisposalPrevious:
+			tmp = prev
+		}
+	}
+	m.Config.Width = size.Dx()
+	m.Config.Height = size.Dy()
+
+	return m, nil
+}
+
+func (g GifGenerator) Dimensions(img any) (image.Rectangle, error) {
+	m, ok := img.(*gif.GIF)
+	if !ok {
+		return image.Rectangle{}, errors.ErrInvalidType
+	}
+	return m.Image[0].Bounds(), nil
+}
+
+func (g GifGenerator) imageToPaletted(img image.Image, p color.Palette) *image.Paletted {
+	b := img.Bounds()
+	pm := image.NewPaletted(b, p)
+	draw.FloydSteinberg.Draw(pm, b, img, image.Point{})
+	return pm
+}
+
+// GeneratorFor returns the generator for a given file type
+// or nil if the type is not supported.
+func GeneratorFor(fileType, processorID string) (Generator, error) {
+	switch strings.ToLower(fileType) {
+	case typePng, typeJpg, typeJpeg, typeGgs, typeGgp, typeWebp:
+		return NewSimpleGenerator(fileType, processorID)
+	case typeGif:
+		return NewGifGenerator(fileType, processorID)
+	default:
+		return nil, errors.ErrNoGeneratorForType
+	}
+}