xcf (decode)

internal/builtins/xcf.go

@@ -0,0 +1,8 @@
+//go:build xcf || full
+// +build xcf full
+
+package builtins
+
+import (
+	_ "github.com/coalaura/ffwebp/internal/codec/xcf"
+)

internal/codec/xcf/xcf.go

@@ -0,0 +1,119 @@
+package xcf
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/color"
+	"image/draw"
+	"io"
+
+	"github.com/gonutz/xcf"
+
+	"github.com/coalaura/ffwebp/internal/codec"
+	"github.com/coalaura/ffwebp/internal/opts"
+	"github.com/urfave/cli/v3"
+)
+
+func init() {
+	codec.Register(impl{})
+}
+
+type impl struct{}
+
+func (impl) String() string {
+	return "xcf"
+}
+
+func (impl) Extensions() []string {
+	return []string{"xcf"}
+}
+
+func (impl) CanEncode() bool {
+	return false
+}
+
+func (impl) Flags(flags []cli.Flag) []cli.Flag {
+	return flags
+}
+
+func (impl) Sniff(reader io.ReaderAt) (int, []byte, error) {
+	magic := []byte("gimp xcf ")
+
+	buf := make([]byte, len(magic))
+	if _, err := reader.ReadAt(buf, 0); err != nil {
+		return 0, nil, err
+	}
+
+	if bytes.Equal(buf, magic) {
+		return 100, magic, nil
+	}
+
+	return 0, nil, nil
+}
+
+func (impl) Decode(r io.Reader) (image.Image, error) {
+	buf, err := io.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+
+	reader := bytes.NewReader(buf)
+
+	canvas, err := xcf.Decode(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	dst := image.NewNRGBA(image.Rect(0, 0, int(canvas.Width), int(canvas.Height)))
+
+	for i := len(canvas.Layers) - 1; i >= 0; i-- {
+		layer := canvas.Layers[i]
+		if !layer.Visible {
+			continue
+		}
+
+		var src image.Image = layer.RGBA
+
+		if layer.Opacity < 255 {
+			src = applyOpacity(src, layer.Opacity)
+		}
+
+		dr := src.Bounds().Intersect(dst.Bounds())
+		if dr.Empty() {
+			continue
+		}
+
+		draw.Draw(dst, dr, src, dr.Min, draw.Over)
+	}
+
+	return dst, nil
+}
+
+func (impl) Encode(w io.Writer, img image.Image, _ opts.Common) error {
+	return fmt.Errorf("xcf: encoding not supported")
+}
+
+func applyOpacity(img image.Image, opacity uint8) *image.NRGBA {
+	bounds := img.Bounds()
+	out := image.NewNRGBA(bounds)
+
+	opa := int(opacity)
+
+	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+		for x := bounds.Min.X; x < bounds.Max.X; x++ {
+			r16, g16, b16, a16 := img.At(x, y).RGBA()
+
+			r := uint8(r16 >> 8)
+			g := uint8(g16 >> 8)
+			b := uint8(b16 >> 8)
+			a := int(uint8(a16 >> 8))
+
+			a = (a*opa + 127) / 255
+
+			out.Set(x, y, color.NRGBA{R: r, G: g, B: b, A: uint8(a)})
+		}
+	}
+
+	return out
+}