使用 Accelerate 缩放 Ycbcr (420f) 时的伪影

Question

我找不到任何关于如何调整 Ycbcr 双平面大小的文档或示例，根据 Apple 的说法，这应该是您应该在 iOS 上使用的主要格式。我试着像这样调整两个平面的大小：

    // resize luma
    vImage_Buffer originalYBuffer = { CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0), CVPixelBufferGetHeightOfPlane(pixelBuffer, 0), CVPixelBufferGetWidthOfPlane(pixelBuffer, 0), CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0) };
    vImage_Buffer resizedYBuffer;
    vImageBuffer_Init(&resizedYBuffer, IMAGE_HEIGHT, IMAGE_WIDTH, 8 * sizeof(Pixel_8), kvImageNoFlags);
    error = vImageScale_Planar8(&originalYBuffer, &resizedYBuffer, NULL, kvImageNoFlags);
    assert(!error);
    cv::Mat grey(IMAGE_HEIGHT, IMAGE_WIDTH, CV_8UC1, resizedYBuffer.data);

    // resize chroma
    vImage_Buffer originalUVBuffer = { CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1), CVPixelBufferGetHeightOfPlane(pixelBuffer, 1), CVPixelBufferGetWidthOfPlane(pixelBuffer, 1), CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 1) };
    vImage_Buffer resizedUVBuffer;
    vImageBuffer_Init(&resizedUVBuffer, IMAGE_HEIGHT / 2, IMAGE_WIDTH / 2, 8 * sizeof(Pixel_16U), kvImageNoFlags);
    error = vImageScale_Planar8(&originalUVBuffer, &resizedUVBuffer, NULL, kvImageNoFlags);
    assert(!error);

但是颜色完全是borked。亮度通道自己工作，所以它是色度的问题。这种格式应该使用 2 个字节的色度，虽然不完全确定。如果我使用 vImageScale_Planar8 我会得到一半的屏幕绿色，否则如果我使用 vImageScale_Planar16U 我会在整个图像中得到 blue/yellow 噪声。

Answer 1

得到苹果大佬的回答：vImageScale_Planar8不能在UV平面上操作，因为它是交错的。唯一的解决办法就是分裂成两个独立的平面。

Answer 2

您可以使用 vImageScale_CbCr8 作为 UV 缓冲区，但它只有 iOS 10+ :

// resize luma
vImage_Buffer originalYBuffer = { CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0), CVPixelBufferGetHeightOfPlane(pixelBuffer, 0), CVPixelBufferGetWidthOfPlane(pixelBuffer, 0), CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0) };
vImage_Buffer resizedYBuffer;
vImageBuffer_Init(&resizedYBuffer, IMAGE_HEIGHT, IMAGE_WIDTH, 8 * sizeof(Pixel_8), kvImageNoFlags);
error = vImageScale_Planar(&originalYBuffer, &resizedYBuffer, NULL, kvImageNoFlags);
assert(!error);
cv::Mat grey(IMAGE_HEIGHT, IMAGE_WIDTH, CV_8UC1, resizedYBuffer.data);

// resize chroma
vImage_Buffer originalUVBuffer = { CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1), CVPixelBufferGetHeightOfPlane(pixelBuffer, 1), CVPixelBufferGetWidthOfPlane(pixelBuffer, 1), CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 1) };
vImage_Buffer resizedUVBuffer;
vImageBuffer_Init(&resizedUVBuffer, IMAGE_HEIGHT / 2, IMAGE_WIDTH / 2, 8 * sizeof(Pixel_16U), kvImageNoFlags);
error = vImageScale_CbCr8(&originalUVBuffer, &resizedUVBuffer, NULL, kvImageNoFlags);
assert(!error);

使用 Accelerate 缩放 Ycbcr (420f) 时的伪影

Artifacts when scaling Ycbcr (420f) with Accelerate

ios

accelerate-framework