texture_select

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This extension allows for better utilization of texture memory by subdividing the internal representation of a texel into 1, 2 or 4 smaller texels.

• The user may then select a subset of those texels as the definition of a texture image.
  
  
• Example:
  a texture format of GL_QUAD_TEXTURE_SELECT_SGIS may have any of its components interpreted as a GL_LUMINANCE texture.
  
  
• This could be used for displaying separate channels of a GIS image interactively.