The destination in the texture array may not include any texels outside the texture array as it was originally specified. The pixels in the row are processed exactly as if glCopyPixels had been called, but the process stops just before final conversion. It is not an error to specify a subtexture with zero width, but such a specification has no effect. No change is made to the internalFormat , width , 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 glCopyTexSubImage1D 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 .