[Pixman] [PATCH 0/7] Tolerance based test program check-formats

[Søren Sandmann]

The following patches add a new program check-formats to the test
directory that takes an operator and two formats and then uses the
reference composite function from composite.c to verify that all
pixels where the red and blue channels are zero composite correctly.

This reveals that in many cases the 8 bit pipeline can't currently
meet the acceptable deviation of 0.004 set in utils.c. Some of the
failing pixels are captured in a new regression test called
pixel-test, which is then made to pass by increasing DEVIATION to
0.0064.

This is all part of a plan to eventually get the test suite to be
based on tolerances instead of bit-exactness so that we have more
flexibility in how to implement fast paths.

However, 0.0064 corresponds to a deviation of 1.64 for an 8-bit
channel, which is more than I'd like, so I'm interested in ideas on
how to improve this (there are some notes in patch 7/7).


Thanks,
Soren