glCopyTexSubImage2D Interface to
OpenGL function glCopyTexSubImage2D
usage: glCopyTexSubImage2D( target, level, xoffset, yoffset, x, y, width, height )
C function: void glCopyTexSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint x, GLint y, GLsizei width, GLsizei height)
Psychtoolbox/PsychOpenGL/MOGL/wrap/glCopyTexSubImage2D.m