The pixels in the rectangle are processed exactly as if glCopyPixels had been called, but the process stops just before final conversion. The destination rectangle in the texture array may not include any texels outside the texture array as it was originally specified. It is not an error to specify a subtexture with zero width or height, but such a specification has no effect. No change is made to the internalformat, width, height, or border parameters of the specified texture array or to texel values outside the specified subregion.
Parameters target Specifies the target texture.
Level 0 is the base image level. Level n is the nth mipmap reduction image. The glCopyTexSubImage2D subroutine is available only if the GL version is 1.1 or greater. Texturing has no effect in color index mode. The glPixelTransfer mode affects texture images in exactly the way they affect glDrawPixels .