pixman-image: Added enable-gnuplot config to view filters in gnuplot
If enable-gnuplot is configured, then you can pipe the output of a
pixman-using program to gnuplot and get a continuously-updated plot of
the horizontal filter. This works well with demos/scale to test the
filter generation.
The plot is all the different subposition filters shuffled
together. This is misleading in a few cases:
IMPULSE.BOX - goes up and down as the subfilters have different
numbers of non-zero samples
IMPULSE.TRIANGLE - somewhat crooked for the same reason
1-wide filters - looks triangular, but a 1-wide box would be more
accurate
Changes by Søren: Rewrote the pixman-filter.c part to
- make it generate correct coordinates
- add a comment on how coordinates are generated
- in rounding.txt, add a ceil() variant of the first-sample
formula
- make the gnuplot output slightly prettier
v7: First time this ability was included
v8: Use config option
Moved code to the filter generator
Modified scale demo to not call filter generator a second time.
v10: Only print if successful generation of plots
Use #ifdef, not #if
v11: small whitespace fixes
v12: output range from -width/2 to width/2 and include y==0, to avoid misleading plots
for subsample_bits==0 and for box filters which may have no small values.
Signed-off-by: Bill Spitzak <spitzak@gmail.com>
3 files changed
