go-libwebp

Experimental translation from libwebp to Go source.
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lib.go (1788B)

      1 package webp
      2 
      3 import (
      4 	"image"
      5 	"io"
      6 
      7 	"git.sr.ht/~jackmordaunt/go-libwebp/v2/lib/common"
      8 	"modernc.org/libc"
      9 )
     10 
     11 func DecodeImpl(buf []byte) (image.Image, error) {
     12 	disableVP8GetCPUInfo()
     13 	tls := libc.NewTLS()
     14 	defer tls.Close()
     15 	return common.Decode(buf, makeDecodeImpl(tls), makeFreeImpl(tls))
     16 }
     17 
     18 func EncodeImpl(w io.Writer, m *image.NRGBA, quality float32) error {
     19 	tls := libc.NewTLS()
     20 	defer tls.Close()
     21 	return common.Encode(w, m, quality, makeEncodeImpl(tls), makeFreeImpl(tls))
     22 }
     23 
     24 func makeDecodeImpl(tls *libc.TLS) common.DecoderFunc {
     25 	return func(data uintptr, data_size uint64, width, height uintptr) uintptr {
     26 		return WebPDecodeRGBA(tls, data, data_size, width, height)
     27 	}
     28 }
     29 
     30 func makeEncodeImpl(tls *libc.TLS) common.EncodeFunc {
     31 	return func(in uintptr, w, h, bps int32, q float32, out uintptr) uint64 {
     32 		if q >= 1.0 {
     33 			return WebPEncodeLosslessRGBA(tls, in, w, h, bps, out)
     34 		}
     35 		return WebPEncodeRGBA(tls, in, w, h, bps, q*100, out)
     36 	}
     37 }
     38 
     39 func makeFreeImpl(tls *libc.TLS) common.FreeFunc {
     40 	return func(p uintptr) {
     41 		WebPFree(tls, p)
     42 	}
     43 }
     44 
     45 func disableVP8GetCPUInfo() {
     46 	// HACK: Avoid panic when decoding lossy webp data.
     47 	//
     48 	// Inline asm is used for CPU feature detection; ccgo doesn't support inline asm.
     49 	//
     50 	// libwebp uses this function pointer to check for any specialized CPU instructions.
     51 	// If not nil (which it is for well supported platforms, like amd64, and arm64), it will try
     52 	// to check CPU features using inline asm. ccgo inserts a panic for inline asm, thus using
     53 	// this will panic.
     54 	//
     55 	// To avoid this terrible fate, we must manually turn off the CPU feature detection by
     56 	// nil'ing out this function pointer. This must be done after package init since that is
     57 	// is when this value is set by the transpiled code.
     58 	VP8GetCPUInfo = 0
     59 }