simon-git: pix (master): Simon Tatham

[Commits to Tartarus CVS repository.]

TL;DR:
  c51ca22 Fix palettisation code in pngout.c.

Repository:     git://git.tartarus.org/simon/pix.git
On the web:     http://tartarus.org/~simon-git/gitweb/?p=pix.git
Branch updated: master
Committer:      Simon Tatham <anakin at pobox.com>
Date:           2016-01-23 08:58:32

commit c51ca227f04b8fe7707b0e9066cc43415bdded34
web diff http://tartarus.org/~simon-git/gitweb/?p=pix.git;a=commitdiff;h=c51ca227f04b8fe7707b0e9066cc43415bdded34;hp=6eb86fed4e78aef4b4482270e0c3b2439b7e3a8b
Author: Simon Tatham <anakin at pobox.com>
Date:   Sat Jan 23 08:55:59 2016 +0000

    Fix palettisation code in pngout.c.
    
    I had a fairly simplistic technique for buliding up a list of the
    colours used in the image, by linearly scanning an array but also
    moving the most recently seen entry to the front at every step, in the
    hope that in practice that would do better than linear time for most
    pixels. Unfortunately, it had a bug in which I was constantly just
    copying the same colour into every position of the array most of the
    time, ahem.
    
    I have to suppose that I hadn't noticed before because _most_ images
    fail the 'can we use a small palette?' test, and if the output image
    type is set to non-paletted then they never need to actually look a
    colour up in this corrupted array at output time. But if an image with
    few enough colours managed to pass the initial test somehow, then it
    would get to the runtime failure.

 pngout.c |   13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)