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. If the GL is in color index mode, each index that is read from this buffer is converted to a fixed-point format with an unspecified number of bits to the right of the binary point. Whether the lookup replacement of the index is done or not, the integer part of the index is then ANDed with 2b -1, where b is the number of bits in a color index buffer. If the GL is in RGBA mode, the red, green, blue, and alpha components of each pixel that is read are converted to an internal floating-point format with unspecified precision.