Its operation is well defined only if the entire pixel source region is within the exposed portion of the window. Results of copies from outside the window, or from regions of the window that are not exposed, are hardware-dependent and undefined. The x and y parameters specify the window coordinates of the lower left corner of the rectangular region to be copied. The Width and Height parameters specify the dimensions of the rectangular region to be copied. Both Width and Height must be nonnegative numbers.
Several parameters control the processing of the pixel data while it is being copied.
This article describes the effects on glCopyPixels of most, but not all, of the parameters specified by these three subroutines. This pixel is said to be the i th pixel in the j th row. Pixels are copied in row order from the lowest to the highest row, left to right in each row. The Type parameter specifies whether color, depth, or stencil data is to be copied. The details of the transfer for each data type are as follows.