Question

Name
glCopyTexImage2D — copy pixels into a 2D texture image

C Specification
void glCopyTexImage2D(GLenum  target,  GLint  level,  GLenum  internalformat,  GLint  x,  GLint  y,  GLsizei  width,  GLsizei  height,  GLint  border);

Apparently, the pixels must be stored somewhere, but where? The function returns void and does not use a pointer parameter.

SO, where does glCopyTexImage2D save its pixels to?

Answer 1

Into a texture you specify as target (e.g. GL_TEXTURE_2D, which would mean currently bound 2D texture). After using that you can use glGetTexImage to fetch the pixels from the texture to your own buffer.