mirror of
https://github.com/wader/fq.git
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114 lines
3.1 KiB
Go
114 lines
3.1 KiB
Go
package riff
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// https://developers.google.com/speed/webp/docs/riff_container
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import (
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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 exifGroup decode.Group
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var iccpGroup decode.Group
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var vp8FrameGroup decode.Group
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var xmlGroup decode.Group
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func init() {
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interp.RegisterFormat(
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format.WebP,
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&decode.Format{
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Description: "WebP image",
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Groups: []*decode.Group{format.Probe, format.Image},
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DecodeFn: webpDecode,
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Dependencies: []decode.Dependency{
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{Groups: []*decode.Group{format.Exif}, Out: &exifGroup},
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{Groups: []*decode.Group{format.VP8_Frame}, Out: &vp8FrameGroup},
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{Groups: []*decode.Group{format.ICC_Profile}, Out: &iccpGroup},
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{Groups: []*decode.Group{format.XML}, Out: &xmlGroup},
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},
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})
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}
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const webpRiffType = "WEBP"
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func webpDecode(d *decode.D) any {
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d.Endian = decode.LittleEndian
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var riffType string
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riffDecode(
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d,
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nil,
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func(d *decode.D, path path) (string, int64) {
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id := d.FieldUTF8("id", 4, scalar.ActualTrimSpace, chunkIDDescriptions)
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size := d.FieldU32("size")
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return id, int64(size)
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},
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func(d *decode.D, id string, path path) (bool, any) {
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switch id {
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case "RIFF":
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riffType = d.FieldUTF8("format", 4, d.StrAssert(webpRiffType))
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return true, nil
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case "VP8":
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d.Format(&vp8FrameGroup, nil)
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return false, nil
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case "VP8L":
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d.FieldU8("signature", d.UintAssert(0x2f), scalar.UintHex)
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n := d.FieldU32("width_height_flags")
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// TODO: replace with "bit endian" decoding
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b0 := (n >> 24) & 0xff
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b1 := (n >> 16) & 0xff
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b2 := (n >> 8) & 0xff
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b3 := (n >> 0) & 0xf
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width := b3 | (b2&0b0011_111)<<8
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width += 1
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height := (b2&0b1100_0000)>>6 | b1<<8 | (b0&0b0000_1111)<<16
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height += 1
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alphaIsUsed := b3&0b0001_0000 != 0
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versionNumber := (b3 & 0b1110_0000) >> 5
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d.FieldValueUint("width", width)
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d.FieldValueUint("height", height)
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d.FieldValueBool("alpha_is_used", alphaIsUsed)
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d.FieldValueUint("version_number", versionNumber)
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d.FieldRawLen("data", d.BitsLeft())
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return false, nil
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case "VP8X":
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d.FieldU2("reserved0")
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d.FieldBool("icc_profile")
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d.FieldBool("alpha")
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d.FieldBool("exif_metadata")
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d.FieldBool("xml_metadata")
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d.FieldBool("animation")
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d.FieldBool("reserved1")
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d.FieldU24("reserved2")
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d.FieldU24("width", scalar.UintActualAdd(1))
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d.FieldU24("height", scalar.UintActualAdd(1))
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return false, nil
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case "EXIF":
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// TODO: where is this documented? both exif in jpeg and webp has this prefix sometimes
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var exifPrefix = []byte("Exif\x00\x00")
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hasExifPrefix := d.TryHasBytes(exifPrefix)
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if hasExifPrefix {
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d.FieldUTF8("exif_prefix", len(exifPrefix))
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}
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d.Format(&exifGroup, nil)
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return false, nil
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case "ICCP":
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d.Format(&iccpGroup, nil)
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return false, nil
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case "XMP":
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d.FieldFormatOrRawLen("data", d.BitsLeft(), &xmlGroup, nil)
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return false, nil
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default:
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d.FieldRawLen("data", d.BitsLeft())
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return false, nil
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}
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})
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if riffType != webpRiffType {
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d.Errorf("wrong or no WEBP riff type found (%s)", riffType)
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}
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return nil
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}
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