Histogram Conformance Test
David Yu, SGI (dyu@engr.sgi.com)

Clear the color buffer
Setup histogram RGBA width == 32 sink == TRUE	- test sink
Get histogram parameters			- test parameters
    format, width, sink, RGBA size
Create a 32x32 RGBA,FLOAT test image

     ------
    |	  .|	Pixels along diagonal have RGBA value
    |	 . |	with distinct component values
    |	.  |
    |  .   |
    | .    |
    |.	   |
     ------

Enable HISTOGRAM
DrawPixels using test image
Get histogram RGBA and reset == TRUE		- test get & reset
TexImage2D using test image
Get histogram RGB and reset == FALSE		- test get
Get histogram A and reset == FALSE
Test that color buffer is still clear		- test sink
Setup histogram RGBA width==32 sink == FALSE	- test reset on redefinition
DrawPixels using test image			- test draw w/o sink
Test that color buffer was updated		- test draw w/o sink
ResetHistogram
ReadPixels using test image			- test read pixels
Get histogram RGBA and reset == TRUE		- test read


Histogram Proxy Conformance Test
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Find largest LUMINANCE histogram
Setup histogram
Check parameters