c++ - Get Pixel color fastest way?

Question

I'm trying to make an auto-cliker for an windows app. It works well, but it's incredibly slow! I'm currently using the method "getPixel" which reloads an array everytime it's called.

Here is my current code:

hdc = GetDC(HWND_DESKTOP);
bx = GetSystemMetrics(SM_CXSCREEN);
by = GetSystemMetrics(SM_CYSCREEN);
start_bx = (bx/2) - (MAX_WIDTH/2);
start_by = (by/2) - (MAX_HEIGHT/2);
end_bx = (bx/2) + (MAX_WIDTH/2);
end_by = (by/2) + (MAX_HEIGHT/2);

for(y=start_by; y<end_by; y+=10)
{   
    for(x=start_bx; x<end_bx; x+=10)
    {
        pixel = GetPixel(*hdc, x, y);
        if(pixel==RGB(255, 0, 0))
        {
            SetCursorPos(x,y);
            mouse_event(MOUSEEVENTF_LEFTDOWN, 0, 0, 0, 0);
            Sleep(50);
            mouse_event(MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
            Sleep(25);
        }
    }
}

So basically, it just scan a range of pixel in the screen and starts a mouse event if it detects a red button.

I know there are other ways to get the pixel color, such as bitblt. But I've made some researches, and I don't understand how I'm supposed to do, in order to scan a color array. I need something which scans screen very fast in order to catch the button.

Could you please help me?

Thanks.

Answer 1

I found a perfect way which is clearly faster than the GetPixel one:

HDC hdc, hdcTemp;
RECT rect;
BYTE* bitPointer;
int x, y;
int red, green, blue, alpha;

while(true)
{
    hdc = GetDC(HWND_DESKTOP);
    GetWindowRect(hWND_Desktop, &rect);
            int MAX_WIDTH = rect.right;
        int MAX_HEIGHT = rect.bottom;

    hdcTemp = CreateCompatibleDC(hdc);
    BITMAPINFO bitmap;
    bitmap.bmiHeader.biSize = sizeof(bitmap.bmiHeader);
    bitmap.bmiHeader.biWidth = MAX_WIDTH;
    bitmap.bmiHeader.biHeight = MAX_HEIGHT;
    bitmap.bmiHeader.biPlanes = 1;
    bitmap.bmiHeader.biBitCount = 32;
    bitmap.bmiHeader.biCompression = BI_RGB;
    bitmap.bmiHeader.biSizeImage = MAX_WIDTH * 4 * MAX_HEIGHT;
    bitmap.bmiHeader.biClrUsed = 0;
    bitmap.bmiHeader.biClrImportant = 0;
    HBITMAP hBitmap2 = CreateDIBSection(hdcTemp, &bitmap, DIB_RGB_COLORS, (void**)(&bitPointer), NULL, NULL);
    SelectObject(hdcTemp, hBitmap2);
    BitBlt(hdcTemp, 0, 0, MAX_WIDTH, MAX_HEIGHT, hdc, 0, 0, SRCCOPY);

    for (int i=0; i<(MAX_WIDTH * 4 * MAX_HEIGHT); i+=4)
    {
        red = (int)bitPointer[i];
        green = (int)bitPointer[i+1];
        blue = (int)bitPointer[i+2];
        alpha = (int)bitPointer[i+3];

        x = i / (4 * MAX_HEIGHT);
        y = i / (4 * MAX_WIDTH);

        if (red == 255 && green == 0 && blue == 0)
        {
            SetCursorPos(x,y);
            mouse_event(MOUSEEVENTF_LEFTDOWN, 0, 0, 0, 0);
            Sleep(50);
            mouse_event(MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
            Sleep(25);
        }
    }
}

I hope this could help someone else.