rename folder extensions -> services

Signed-off-by: Christian Richter <crichter@owncloud.com>

services/thumbnails/pkg/thumbnail/generator.go

@@ -0,0 +1,88 @@
+package thumbnail
+
+import (
+	"errors"
+	"image"
+	"image/color"
+	"image/draw"
+	"image/gif"
+	"strings"
+
+	"github.com/disintegration/imaging"
+)
+
+var (
+	// ErrInvalidType represents the error when a type can't be encoded.
+	ErrInvalidType2 = errors.New("can't encode this type")
+	// ErrNoGeneratorForType represents the error when no generator could be found for a type.
+	ErrNoGeneratorForType = errors.New("no generator for this type found")
+)
+
+type Generator interface {
+	GenerateThumbnail(image.Rectangle, interface{}) (interface{}, error)
+}
+
+type SimpleGenerator struct{}
+
+func (g SimpleGenerator) GenerateThumbnail(size image.Rectangle, img interface{}) (interface{}, error) {
+	m, ok := img.(image.Image)
+	if !ok {
+		return nil, ErrInvalidType2
+	}
+
+	return imaging.Thumbnail(m, size.Dx(), size.Dy(), imaging.Lanczos), nil
+}
+
+type GifGenerator struct{}
+
+func (g GifGenerator) GenerateThumbnail(size image.Rectangle, img interface{}) (interface{}, error) {
+	// Code inspired by https://github.com/willnorris/gifresize/blob/db93a7e1dcb1c279f7eeb99cc6d90b9e2e23e871/gifresize.go
+
+	m, ok := img.(*gif.GIF)
+	if !ok {
+		return nil, ErrInvalidType2
+	}
+	// 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)
+		scaled := imaging.Resize(tmp, size.Dx(), size.Dy(), imaging.Lanczos)
+		m.Image[i] = g.imageToPaletted(scaled, 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) 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
+}
+
+// GeneratorForType returns the generator for a given file type
+// or nil if the type is not supported.
+func GeneratorForType(fileType string) (Generator, error) {
+	switch strings.ToLower(fileType) {
+	case typePng, typeJpg, typeJpeg:
+		return SimpleGenerator{}, nil
+	case typeGif:
+		return GifGenerator{}, nil
+	default:
+		return nil, ErrNoEncoderForType
+	}
+}