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提供維基 的內容：

OpenGL 2.1 was released on August 2, 2006 and is backward compatible with all prior OpenGL versions.[13] OpenGL 2.1 incorporates the following functionality:

* OpenGL Shading Language revision 1.20 (GLSL)
* Commands to specify and query non-square matrix uniforms for use with the OpenGL Shading Language
* Pixel buffer objects for efficient image transfers to and from buffer objects for commands such as glTexImage2D and glReadPixels.

This functionality corresponds to the ARB_pixel_buffer_object extension.

* sRGB texture formats.

This functionality corresponds to the EXT_texture_sRGB extension.