   16-bit (565) with glTexImage2D
  Does anyone know the correct parameters to use with glTexImage2D to get a 16-bit (565) texture?  I always get a GL_INVALID_ENUM error with whatever I try.  Thanks.   
  Well, you can't reliably get a 16 bit RGB565 texture. The closest you can get is setting the internal format to GL_RGB5, which would request the texture to be stored with 5 bits for each channel, that is, not 6 for the green one. But the internal formats are only hints and the driver is free to pick any sized format it wants to, as long as the number of requested components doesn't change.However, if would make more sense to give a 16-bit 565 image to OpenGL, which I assume is what you mean. Then you would have to find the proper conbination for the third and second last parameter. Depending on how the pixels are packed into the 16 bits, you have to find the correct combination of the third last parameter (GL_RGB in this case) and the second last parameter (either GL_UNSIGNED_SHORT_5_6_5 or GL_UNSIGNED_SHORT_5_6_5_REV). Try and see which one works.   