tree 9edf445ae3aae1a3c671ac7e08147f3aae035d09
parent ec5adb83dd38d31374670129851cccc729b9ce13
author Jonathan Wright <jonathan.wright@arm.com> 1557406013 +0100
committer DRC <information@libjpeg-turbo.org> 1562079324 -0500

Use bias pattern for 4:4:0 (h1v2) fancy upsampling

This commit modifies h1v2_fancy_upsample() so that it uses an ordered
dither pattern, similar to that of h2v1_fancy_upsample(), rounding up or
down the result for alternate pixels rather than always rounding down.
This ensures that the decompression error pattern for a 4:4:0 JPEG image
will be similar to the rotated decompression error pattern for a 4:2:2
JPEG image.  Thus, the final result will be similar regardless of
whether a 4:2:2 JPEG image is rotated or transposed before or after
decompression.

Closes #356