从 HBITMAP 获取特定像素的 RGB 值

Question

如何从HBITMAP中获取一个特定的像素RGB值？我尝试在StackOverflow上阅读类似的帖子，但没有一个真正适合这个问题。下面的代码似乎在HBITMAP中获得了另一个位置（不是想要的位置）的RGB值。

    int width = rc.right - rc.left;
    int height = rc.bottom - rc.top;
    HDC hdcSource = hdc; // the source device context
    HBITMAP hSource = hbmp; // the bitmap selected into the device context
    BITMAPINFO MyBMInfo = {0};
    MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
    // Get the BITMAPINFO structure from the bitmap
    if(0 == GetDIBits(hdcSource, hSource, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS))
    {
        // error handling
    }
    // create the pixel buffer
    BYTE* Pixels = new BYTE[MyBMInfo.bmiHeader.biSizeImage];
    // We'll change the received BITMAPINFOHEADER to request the data in a
    // 32 bit RGB format (and not upside-down) so that we can iterate over
    // the pixels easily. 
    // requesting a 32 bit image means that no stride/padding will be necessary,
    // although it always contains an (possibly unused) alpha channel
    MyBMInfo.bmiHeader.biBitCount = 32;
    MyBMInfo.bmiHeader.biCompression = BI_RGB;  // no compression -> easier to use
    // correct the bottom-up ordering of lines (abs is in cstdblib and stdlib.h)
    MyBMInfo.bmiHeader.biHeight = abs(MyBMInfo.bmiHeader.biHeight);
    // Call GetDIBits a second time, this time to (format and) store the actual
    // bitmap data (the "pixels") in the buffer lpPixels
    if(0 == GetDIBits(hdcSource, hSource, 0, MyBMInfo.bmiHeader.biHeight,
                      Pixels, &MyBMInfo, DIB_RGB_COLORS))
    {
        // error handling
    }
    int PixelX = 221;
    int PixelY = 14;
    cout << "R: " << (int)Pixels[4*((PixelX-1)+(PixelY-1)*width)] << " | G: " << (int)Pixels[4*((PixelX-1)+(PixelY-1)*width)+1] << " | B: " << (int)Pixels[4*((PixelX-1)+(PixelY-1)*width)+2] << endl;

编辑（使用用户1118321的解决方案）

height-1，因为 y 从 0 而不是 1 开始。

cout << "R: " << (int)Pixels[4*((PixelX)+(height-1-(PixelY))*width)] << " | G: " << (int)Pixels[4*((PixelX)+(height-1-(PixelY))*width)+1] << " | B: " << (int)Pixels[4*((PixelX)+(height-1-(PixelY))*width)+2] << endl;

Answer 1

Windows 位图从左下角开始存储其像素，Y 向上增加。尝试使用((height - 1) - PixelY)而不仅仅是PixelY，看看是否有帮助。