Each element is a single value, a color index. The GL converts it to fixed point (with an unspecified number of zero bits to the right of the binary point), shifted left or right depending on the value and sign of
GL_INDEX_SHIFT, and added to
glPixelTransfer). The resulting index is converted to a set of color components using the
GL_PIXEL_MAP_I_TO_A tables, and clamped to the range [0,1].
Each element is a single red component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for green and blue, and 1 for alpha. Each component is then multiplied by the signed scale factor
GL_c_SCALE, added to ...