png

internal/codec/png/png.go

@@ -0,0 +1,88 @@
+package png
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/png"
+	"io"
+
+	"github.com/coalaura/ffwebp/internal/codec"
+	"github.com/coalaura/ffwebp/internal/opts"
+	"github.com/urfave/cli/v3"
+)
+
+var (
+	compression int
+)
+
+type impl struct{}
+
+func init() {
+	codec.Register(impl{})
+}
+
+func (impl) Name() string {
+	return "png"
+}
+
+func (impl) Extensions() []string {
+	return []string{"png"}
+}
+
+func (impl) Flags(flags []cli.Flag) []cli.Flag {
+	return append(flags, &cli.IntFlag{
+		Name:        "png.compression",
+		Usage:       "PNG: compression level (0=default, 1=none, 2=speed, 3=best)",
+		Value:       0,
+		Destination: &compression,
+		Validator: func(value int) error {
+			if value < 0 || value > 4 {
+				return fmt.Errorf("invalid compression level: %q", value)
+			}
+
+			return nil
+		},
+	})
+}
+
+func (impl) Sniff(reader io.ReaderAt) (int, error) {
+	magic := []byte{0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A}
+
+	buf := make([]byte, len(magic))
+
+	if _, err := reader.ReadAt(buf, 0); err != nil {
+		return 0, err
+	}
+
+	if bytes.Equal(buf, magic) {
+		return 100, nil
+	}
+
+	return 0, nil
+}
+
+func (impl) Decode(reader io.Reader) (image.Image, error) {
+	return png.Decode(reader)
+}
+
+func (impl) Encode(writer io.Writer, img image.Image, _ opts.Common) error {
+	encoder := png.Encoder{
+		CompressionLevel: compressionLevel(compression),
+	}
+
+	return encoder.Encode(writer, img)
+}
+
+func compressionLevel(level int) png.CompressionLevel {
+	switch level {
+	case 1:
+		return png.NoCompression
+	case 2:
+		return png.BestSpeed
+	case 3:
+		return png.BestCompression
+	default:
+		return png.DefaultCompression
+	}
+}