NV12截图_js 截图

//裁剪的坐标X和Y必须是偶数，否则UV和Y会有偏差, 注意点，linesize对其为1
int NV12CropTo420P(uint8_t *nv12data, int width, int height, int cropx,
int cropy, uint8_t *yuv420pdata, int dscw, int dsch) { 

uint8_t *ptry = yuv420pdata, *ptru, *ptrv;
uint8_t *nvptr = nv12data + width * height;
ptry = yuv420pdata;
ptru = yuv420pdata + dscw * dsch; //u
ptrv = yuv420pdata + dscw * dsch + (dscw * dsch) / 4; //v
for (int y = cropy; y < dsch + cropy /*pFrame->height*/; y++) { 

memcpy(ptry, nv12data + y * width + cropx, dscw);
ptry += dscw;
}
for (int nvy = cropy / 2; nvy < dsch / 2 + cropy / 2 /*height / 2*/;
nvy++) { 

//-----w-----
//Y Y Y Y
//Y Y Y Y
//Y Y Y Y
//Y Y Y Y
//U V U V
//U V U V
for (int nvx = cropx; nvx < dscw + cropx; nvx++) { 

//如果目标是ffmpeg的avframe则需要注意的是linesize
if (nvx % 2 == 0) { 

*ptru++ = nvptr[nvy * width + nvx]; //u
} else { 

*ptrv++ = nvptr[nvy * width + nvx]; //v
}
}
}
return 0;
}