我正在嘗試使用 libswscale 在使用 cgo 編碼為 h264 之前縮放圖像。這里我寫了一個(gè)簡(jiǎn)單的demo（抱歉代碼風(fēng)格不好，我只是想快速驗(yàn)證一下）：func scale(img []byte, scaleFactor int) { input, _, _ := image.Decode(bytes.NewReader(img)) if a, ok := input.(*image.YCbCr); ok { width, height := a.Rect.Dx(), a.Rect.Dy() var format C.enum_AVPixelFormat = C.AV_PIX_FMT_YUV420P context := C.sws_getContext(C.int(width), C.int(height), format, C.int(width/scaleFactor), C.int(height/scaleFactor), 0, C.int(0x10), nil, nil, nil) in := make([]uint8, 0) in = append(in, a.Y...) in = append(in, a.Cb...) in = append(in, a.Cr...) stride := []C.int{C.int(width), C.int(width / 2), C.int(width / 2), 0} outstride := []C.int{C.int(width / scaleFactor), C.int(width / scaleFactor / 2), C.int(width / scaleFactor / 2), 0} out := make([]uint8, width*height/scaleFactor/scaleFactor*3/2) C.sws_scale(context, (**C.uint8_t)(unsafe.Pointer(&in[0])), (*C.int)(&stride[0]), 0, C.int(height), (**C.uint8_t)(unsafe.Pointer(&out[0])), (*C.int)(&outstride[0])) min := image.Point{0, 0} max := image.Point{width / scaleFactor, height / scaleFactor} output := image.NewYCbCr(image.Rectangle{Min: min, Max: max}, image.YCbCrSubsampleRatio420) paneSize := width * height / scaleFactor / scaleFactor output.Y = out[:paneSize] output.Cb = out[paneSize : paneSize*5/4] output.Cr = out[paneSize*5/4:] opt := jpeg.Options{ Quality: 90, } f, _ := os.Create("img.jpeg") jpeg.Encode(f, output, &opt) }}每次我運(yùn)行代碼片段時(shí)，我都會(huì)收到一條錯(cuò)誤消息bad dst image pointers，說我的代碼有什么問題。我是cgo的新手，所以代碼對(duì)你來說可能很愚蠢，我為此道歉。如果您有更優(yōu)雅的方式來實(shí)現(xiàn)功能，我會(huì)全力以赴。任何建議將不勝感激。
2 回答
qq_花開花謝_0
TA貢獻(xiàn)1835條經(jīng)驗(yàn) 獲得超7個(gè)贊
swscale 需要一個(gè)二維數(shù)組。那是指向指針數(shù)組的指針。每個(gè)指針指向圖像的不同平面 (y,u,v)。您正在制作一個(gè)緩沖區(qū)并將指針傳遞給該緩沖區(qū)的指針。沒有指向 swscale 的 U 和 V 平面的指針。因此，不好的指針。
倚天杖
TA貢獻(xiàn)1828條經(jīng)驗(yàn) 獲得超3個(gè)贊
事實(shí)證明，我的輸入和輸出緩沖區(qū)都是錯(cuò)誤的，它們都需要是@szatmary 提到的二維數(shù)組。這是工作代碼
func Scale(img []byte, outw, outh int) []byte {
input, _, _ := image.Decode(bytes.NewReader(img))
if a, ok := input.(*image.YCbCr); ok {
width, height := a.Rect.Dx(), a.Rect.Dy()
var format C.enum_AVPixelFormat = C.AV_PIX_FMT_YUV420P
context := C.sws_getContext(C.int(width), C.int(height), format, C.int(outw), C.int(outh), 0, C.int(0x10), nil, nil, nil)
y := (*C.uint8_t)(C.malloc(C.ulong(len(a.Y))))
C.memcpy(unsafe.Pointer(y), unsafe.Pointer(&a.Y[0]), (C.size_t)(len(a.Y)))
cb := (*C.uint8_t)(C.malloc(C.ulong(len(a.Cb))))
C.memcpy(unsafe.Pointer(cb), unsafe.Pointer(&a.Cb[0]), (C.size_t)(len(a.Cb)))
cr := (*C.uint8_t)(C.malloc(C.ulong(len(a.Cr))))
C.memcpy(unsafe.Pointer(cr), unsafe.Pointer(&a.Cr[0]), (C.size_t)(len(a.Cr)))
in := []*C.uint8_t{y, cb, cr}
stride := []C.int{C.int(a.YStride), C.int(a.CStride), C.int(a.CStride), 0}
outstride := []C.int{C.int(outw), C.int(outw / 2), C.int(outw / 2), 0}
paneSize := outw * outh
a := (*C.uint8_t)(C.malloc(C.ulong(paneSize)))
b := (*C.uint8_t)(C.malloc(C.ulong(paneSize >> 2)))
c := (*C.uint8_t)(C.malloc(C.ulong(paneSize >> 2)))
out := []*C.uint8_t{a, b, c}
C.sws_scale(context, (**C.uint8_t)(unsafe.Pointer(&in[0])), (*C.int)(&stride[0]), 0,
C.int(height), (**C.uint8_t)(unsafe.Pointer(&out[0])), (*C.int)(&outstride[0]))
min := image.Point{0, 0}
max := image.Point{outw, outh}
output := image.NewYCbCr(image.Rectangle{Min: min, Max: max}, image.YCbCrSubsampleRatio420)
C.memcpy(unsafe.Pointer(&output.Y[0]), unsafe.Pointer(a), (C.size_t)(paneSize))
C.memcpy(unsafe.Pointer(&output.Cb[0]), unsafe.Pointer(b), (C.size_t)(paneSize>>2))
C.memcpy(unsafe.Pointer(&output.Cr[0]), unsafe.Pointer(c), (C.size_t)(paneSize>>2))
opt := jpeg.Options{
Quality: 75,
}
var buf bytes.Buffer
w := bufio.NewWriter(&buf)
jpeg.Encode(w, output, &opt)
return buf.Bytes()
}
return nil
}
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