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• 原始数据第 height - 2 行第 0 列的像素点将会变成目标数据第 1 行第 0 列的像素点

• 原始数据第 height - 2 行第 1 列的像素点将会变成目标数据第 1 行第 1 列的像素点

• …

• 原始数据第 height - 2 行第 width - 1 列的像素点将会变成目标数据第 1 行第 width - 1 列的像素点

• …

• 原始数据第 height - 1 行第 0 列的像素点将会变成目标数据第 0 行第 0 列的像素点

• 原始数据第 height - 1 行第 1 列的像素点将会变成目标数据第 0 行第 1 列的像素点

• …

• 原始数据第 height - 1 行第 width - 1 列的像素点将会变成目标数据第 0 行第 width - 1 列的像素点

二、镜像BGR24 / RGB24

由于BGR数据是3个byte作为一个像素点，因此我们在拷贝每个像素时需要每次移动3个byte。

• 水平镜像

void horizontalMirrorBgr24(char *bgr24, char *mirrorBgr24, int width, int height) {

int lineStartIndex = 0;

int lineDataSize = width * 3;

for (int h = 0; h < height; h++) {

for (int w = 0; w < lineDataSize; w += 3) {

mirrorBgr24[lineStartIndex + w] = bgr24[lineStartIndex + lineDataSize - w - 3];

mirrorBgr24[lineStartIndex + w + 1] = bgr24[lineStartIndex + lineDataSize - w - 2];

mirrorBgr24[lineStartIndex + w + 2] = bgr24[lineStartIndex + lineDataSize - w - 1];

}

lineStartIndex += lineDataSize;

}

}

• 垂直镜像

void verticalMirrorBgr24(char *bgr24, char *mirrorBgr24, int width, int height) {

int lineDataSize = width * 3
;

bgr24 += width * height * 3;

for (int h = 0; h < height; h++) {

memcpy(mirrorBgr24, bgr24, lineDataSize);

mirrorBgr24 += lineDataSize;

bgr24 -= lineDataSize;

}

}

三、镜像NV21 / NV12

由于NV21和NV12的结构只是UV数据位置相反，因此镜像NV21的代码同样适用于镜像NV12。

• 水平镜像

void horizontalMirrorNv21(char *nv21, char *mirrorNv21, int width, int height) {

int yLineStartIndex = 0;

int uvLineStartIndex = width * height;

for (int h = 0; h < height; h++) {

for (int w = 0; w < width; w += 2) {

mirrorNv21[yLineStartIndex + w] = nv21[yLineStartIndex + width - w];

mirrorNv21[yLineStartIndex + w + 1] = nv21[yLineStartIndex + width - w - 1];

if ((h & 1) == 0) {

mirrorNv21[uvLineStartIndex + w] = nv21[uvLineStartIndex + width - w];

mirrorNv21[uvLineStartIndex + w + 1] = nv21[uvLineStartIndex + width - w - 1];

}

}

yLineStartIndex += width;

if ((h & 1) == 0) {

uvLineStartIndex += width;

}

}

}

• 垂直镜像

void verticalMirrorNv21(char *nv21, char *mirrorNv21, int width, int height) {

int yLineDataSize = width;

int nv21Index = 0, mirrorNv21Index = 0;

nv21Index += width * height - yLineDataSize;

//mirror y

for (int h = 0; h < height; h++) {

memcpy(mirrorNv21 + mirrorNv21Index, nv21 + nv21Index, yLineDataSize);

mirrorNv21Index += yLineDataSize;

nv21Index -= yLineDataSize;

}

int uvLineDataSize = width;

//mirror uv

int uvHeight = height / 2;

//point to final line of uv

nv21Index += (width * height * 3 / 2 - uvLineDataSize);

for (int h = 0; h < uvHeight; h++) {

memcpy(mirrorNv21 + mirrorNv21Index, nv21 + nv21Index, uvLineDataSize);

mirrorNv21Index += uvLineDataSize;

nv21Index -= uvLineDataSize;

}

}

四、镜像I420 / YV12

由于I420 和YV12的结构只是UV数据位置相反，因此镜像I420的代码同样适用于镜像YV12。

• 水平镜像

void horizontalMirrorI420(char *i420, char *mirrorI420, int width, int height) {

int yLineStartIndex = 0;

int uLineStartIndex = width * height;

int vLineStartIndex = width * height * 5 / 4;

for (int h = 0; h < height; h++) {

for (int w = 0; w < width; w += 2) {

mirrorI420[yLineStartIndex + w] = i420[yLineStartIndex + width - w];

mirrorI420[yLineStartIndex + w + 1] = i420[yLineStartIndex + width - w - 1];

if ((h & 1) == 0) {

mirrorI420[uLineStartIndex + (w >> 1)] = i420[uLineStartIndex + ((width - w) >> 1)];

mirrorI420[vLineStartIndex + (w >> 1) + 1] = i420[vLineStartIndex +

((width - w) >> 1) - 1];

}

}

yLineStartIndex += width;

if ((h & 1) == 0) {

uLineStartIndex += width >> 1;

vLineStartIndex += width >> 1;

}

}

}

• 垂直镜像

void verticalMirrorI420(char *i420, char *mirrorI420, int width, int height) {

int halfWidth = width / 2;

int yLineDataSize = width;

int i420Index = 0, mirrorI420Index = 0;

i420Index += width * height - yLineDataSize;

//mirror y

for (int h = 0; h < height; h++) {

memcpy(mirrorI420 + mirrorI420Index, i420 + i420Index, yLineDataSize);

mirrorI420Index += yLineDataSize;

i420Index -= yLineDataSize;

}

int uvLineDataSize = halfWidth;

//mirror uv

;

i420Index += width * height - yLineDataSize;

//mirror y

for (int h = 0; h < height; h++) {

memcpy(mirrorI420 + mirrorI420Index, i420 + i420Index, yLineDataSize);

mirrorI420Index += yLineDataSize;

i420Index -= yLineDataSize;

}

int uvLineDataSize = halfWidth;

//mirror uv