YUV4:2:2 UYVY图像旋转

最新推荐文章于 2022-07-01 20:00:00 发布

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最新推荐文章于 2022-07-01 20:00:00 发布

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本文介绍YUV4:2:2 UYVY格式图像的旋转算法实现，包括90度、180度和270度旋转，并确保旋转过程中UYVY结构不变及Y分量位置正确。

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原文：http://blog.youkuaiyun.com/zhangyonggen/article/details/48522593

YUV4:2:2 UYVY 格式在内存中的存储方式为交织类型，内存中的存储方式为：UYVY UYVY UYVY...........，Y为亮度信息，UV为色度信息，YUV4:2:2是每两个像素点共用一对UV分量，每个像素点的Y分量是独立的，UV分量是共享的，所以一幅图像的总的字节数totalBytes = width × height + width * height / 2 + width * height / 2 = width * height * 2；在进行旋转操作是必须满足UYVY的结构不变即4个字节为一组，否则会产生颜色不对、锯齿等，也必须保证Y分量在相应的位置上：

1、旋转90度

bool Rotate90(unsigned char *src, int width, int height)
{
        const int copyBytes    = 4;
        const int bytesPerLine = width << 1;
        const int step         = height  << 2;
        const int offset       = (height - 1) * bytesPerLine;
        unsigned char *dst     = new (std::nothrow)BYTE[bytesPerLine * height];
        if(NULL == dst)
        {
             return false;
        }
        unsigned char * dest       = dst;
        unsigned char * source  = src;
        unsigned char * psrc       = NULL;
        unsigned char * pdst[2]   = {NULL, NULL};

for (int i = 0; i < bytesPerLine; i += copyBytes)
{
pdst[0] = dest;
pdst[1] = dest   + (height << 1);
psrc    = source + offset;

for (int j = 0; j < height; ++j)
{
int k = j % 2;

// 拷贝4个字节
*((unsigned int *)pdst[k]) = *((unsigned int *)psrc);
            
// Y分量交换，保证每个像素点的亮度不改变否则产生锯齿
if(1 == k)
{
unsigned char temp = *(pdst[0] - 1);
*(pdst[0] - 1) = *(pdst[1] + 1);
*(pdst[1] + 1) = temp;
}
            
pdst[k] += copyBytes;
psrc    -= bytesPerLine;
}

dest   += step;
source += copyBytes;
}

        memcpy(src, dst, width * height * 2);

        delete[] dst;
        return true;
}

2、旋转180度

旋转180度相对来说较为简单，从左上角开始与右下角相互交换，由于每两个像素点共享一对UV分量，所以交换的字节数为4字节，但是还需要保证Y分量的位置正确，所以还需要交换Y分量。

bool Rotate180(unsigned char *src, int width, int height)
{
        const int copyBytes  = 4;
const int totalBytes = height * width << 1;
        const int end           = totalBytes >> 1;
unsigned char *dst   = src + totalBytes - copyBytes;

for (int i = 0; i < end; i += copyBytes)
{
                unsigned int tmp       = *((unsigned int *)dst);
*((unsigned int *)dst) = *((unsigned int *)src);
                *((unsigned int *)src) = tmp;

               // 交换Y分量
unsigned char temp = dst[1];
dst[1] = dst[3];
dst[3] = temp;

                temp   = src[1];
src[1] = src[3];
src[3] = temp;

dst -= copyBytes;
src += copyBytes;
}

    return true;
}

3、旋转270度

与旋转90度相类似

bool Rotate270(unsigned char *src, int width, int height)
{
        const int copyBytes    = 4;
const int bytesPerLine = width << 1;
const int step         = height << 2;
const int offset       = bytesPerLine - copyBytes;
        unsigned char *dst     = new (std::nothrow)BYTE[bytesPerLine * height];
        if(NULL == dst)
        {
             return false;
        }
        unsigned char *dest    = dst;
        unsigned char *source  = src;
        unsigned char *psrc    = NULL;
        unsigned char *pdst[2] = {NULL, NULL};

for (int i = 0; i < bytesPerLine; i += copyBytes)
{
pdst[1] = dest;
pdst[0] = dest + (height << 1);
psrc    = source + offset;


for (int j = 0; j < height; ++j)
{
int k = j % 2;

*((unsigned int *)pdst[k]) = *((unsigned int *)psrc);

if(1 == k)
{
unsigned char temp      = *(pdst[1] + 1);
*(pdst[1] + 1) = *(pdst[0] - 1);
*(pdst[0] - 1) = temp;
}

pdst[k] += copyBytes;
psrc    += bytesPerLine;
}

dest   += step;
source -= copyBytes;
}

        memcpy(src, dst, width * height * 2);

        delete[] dst;
        return true;
}