How to read the screen pixels?

Question

I want to read a rectangular area, or whole screen pixels. As if screenshot button was pressed.

How i do this?

Edit: Working code:

Answer 1

Rereading your question, it sounds like we may have gotten off on a tangent with the screen capture. If you just want to check some pixels on the screen, you can use GetPixel.

HDC hdcScreen = ::GetDC(NULL);
COLORREF pixel = ::GetPixel(hdcScreen, x, y);
ReleaseDC(NULL, hdcScreen);
if (pixel != CLR_INVALID) {
  int red = GetRValue(pixel);
  int green = GetGValue(pixel);
  int blue = GetBValue(pixel);
  ...
} else {
  // Error, x and y were outside the clipping region.
}

If you're going to read a lot of pixels, then you're better off with a screen capture and then using GetDIBits. Calling GetPixel zillions of times will be slow.