win32截屏並rgb24轉yuv420

//最終f的內存布局為BGRA格式，需要保證buf長度足夠(>w*h*4)
void ScreenCap(void* buf, int w, int h)
{

HWND hDesk = GetDesktopWindow();
HDC hScreen = GetDC(hDesk);
int width = w;//GetDeviceCaps(hScreen, HORZRES);
int height = h;//GetDeviceCaps(hScreen, VERTRES);

// if (w != 0)
// *w = width;
// if (h != 0)
// *h = height;

HDC hdcMem = CreateCompatibleDC(hScreen);
HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, width, height);

BITMAPINFOHEADER bmi = { 0 };
bmi.biSize = sizeof(BITMAPINFOHEADER);
bmi.biPlanes = 1;
bmi.biBitCount = 24;
bmi.biWidth = width;
bmi.biHeight = height;
bmi.biCompression = BI_RGB;
bmi.biSizeImage = width*height;

SelectObject(hdcMem, hBitmap);
BitBlt(hdcMem, 0, 0, width, height, hScreen, 0, 0, SRCCOPY);

GetDIBits(hdcMem, hBitmap, 0, height, buf, (BITMAPINFO*)&bmi, DIB_RGB_COLORS);

DeleteDC(hdcMem);
ReleaseDC(hDesk, hScreen);
CloseWindow(hDesk);
DeleteObject(hBitmap);
}

//////////////////////////////////////////////////////////////////////////
// rgb轉yuv420
//////////////////////////////////////////////////////////////////////////
bool RGB2YUV(unsigned char* RgbBuf,UINT nWidth,UINT nHeight,LPBYTE yuvBuf,unsigned long len)
{
int i, j;
unsigned char*bufY, *bufU, *bufV, *bufRGB,*bufYuv;
memset(yuvBuf,0,nWidth*nHeight*1.5);
bufY = yuvBuf;
bufV = yuvBuf + nWidth * nHeight;
bufU = bufV + (nWidth * nHeight* 1/4);

unsigned char y, u, v, r, g, b,testu,testv;
unsigned int ylen = nWidth * nHeight;
unsigned int ulen = (nWidth * nHeight)/4;
unsigned int vlen = (nWidth * nHeight)/4;
for (j = 0; j<nHeight;j++)
{
bufRGB = RgbBuf + nWidth * (nHeight - 1 - j) * 3 ;
for (i = 0;i<nWidth;i++)
{
int pos = nWidth * i + j;
r = *(bufRGB++);
g = *(bufRGB++);
b = *(bufRGB++);
y = (unsigned char)( ( 66 * r + 129 * g + 25 * b + 128) >> 8) + 16 ;
u = (unsigned char)( ( -38 * r - 74 * g + 112 * b + 128) >> 8) + 128 ;
v = (unsigned char)( ( 112 * r - 94 * g - 18 * b + 128) >> 8) + 128 ;
*(bufY++) = max( 0, min(y, 255 ));
if (j%2==0&&i%2 ==0)
{
if (u>255)
{
u=255;
}
if (u<0)
{
u = 0;
}
*(bufU++) =u;
//存u分量
}
else
{
//存v分量
if (i%2==0)
{
if (v>255)
{
v = 255;
}
if (v<0)
{
v = 0;
}
*(bufV++) =v;
}
}
}
}
//len = nWidth * nHeight+(nWidth * nHeight)/2;
return true;
}

char*rgb=new char[width*height*3];
ScreenCap(rgb,width,height);
RGB2YUV((unsigned char*)rgb,width,height, yuv_buffer,0);

這樣獲得的yuv420 可以直接x264 encode 壓縮成視頻。即屏幕錄像或者屏幕直播

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