mirror of https://github.com/stashapp/stash.git
47 lines
1002 B
Go
47 lines
1002 B
Go
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package image
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import (
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"bytes"
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)
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const (
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formatWebP = "webp"
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formatGif = "gif"
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)
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// https://developers.google.com/speed/webp/docs/riff_container
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func isWebPAnimated(buf []byte) bool {
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const (
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webPHeaderStart = 8
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webPHeaderEnd = 12
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webPHeader = "WEBP"
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animationHeaderLoc = 16
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minAnimSignatureIndex = 20
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maxSize = 48
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)
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// truncate the buffer to the max size
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if len(buf) > maxSize {
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buf = buf[:maxSize]
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}
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isWebp := len(buf) >= webPHeaderEnd && string(buf[webPHeaderStart:webPHeaderEnd]) == "WEBP" // is WEBP
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if isWebp {
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const animBit byte = 1 << 1
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if len(buf) > minAnimSignatureIndex {
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// Animation Bit is set and ANIM header is present
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return (buf[animationHeaderLoc]&animBit == animBit) && containsAnimSignature(buf[minAnimSignatureIndex:])
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}
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}
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return false
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}
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// https://developers.google.com/speed/webp/docs/riff_container#animation
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func containsAnimSignature(buf []byte) bool {
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index := bytes.Index(buf, []byte("ANIM"))
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return index != -1
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}
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