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74 lines
1.6 KiB
Go
74 lines
1.6 KiB
Go
package webp
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// https://developers.google.com/speed/webp/docs/riff_container
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import (
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"bytes"
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"github.com/wader/fq/format"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/interp"
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"github.com/wader/fq/pkg/scalar"
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)
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var vp8Frame decode.Group
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func init() {
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interp.RegisterFormat(decode.Format{
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Name: format.WEBP,
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Description: "WebP image",
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Groups: []string{format.PROBE, format.IMAGE},
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DecodeFn: webpDecode,
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Dependencies: []decode.Dependency{
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{Names: []string{format.VP8_FRAME}, Group: &vp8Frame},
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},
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})
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}
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func decodeChunk(d *decode.D, expectedChunkID string, fn func(d *decode.D)) {
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trimChunkID := d.FieldUTF8("id", 4, scalar.ActualTrimSpace)
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if expectedChunkID != "" && trimChunkID != expectedChunkID {
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return
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}
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chunkLen := int64(d.FieldU32("size"))
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if fn != nil {
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d.FramedFn(chunkLen*8, fn)
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} else {
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d.FieldRawLen("data", chunkLen*8)
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}
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}
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func webpDecode(d *decode.D, _ any) any {
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d.Endian = decode.LittleEndian
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d.FieldUTF8("riff_id", 4, d.AssertStr("RIFF"))
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riffLength := d.FieldU32("riff_length")
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d.FieldUTF8("webp_id", 4, d.AssertStr("WEBP"))
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d.FramedFn(int64(riffLength-4)*8, func(d *decode.D) {
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p := d.PeekBytes(4)
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// TODO: VP8X
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switch {
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case bytes.Equal(p, []byte("VP8 ")):
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d.FieldStruct("image", func(d *decode.D) {
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decodeChunk(d, "VP8", func(d *decode.D) {
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d.Format(vp8Frame, nil)
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})
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})
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case bytes.Equal(p, []byte("VP8L")):
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d.FieldStruct("image", func(d *decode.D) {
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decodeChunk(d, "VP8L", func(d *decode.D) {
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// TODO
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})
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})
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default:
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d.Fatalf("could not find VP8 or VP8L chunk")
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}
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})
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return nil
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}
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