On Thu, 24 Jun 2010 06:04:57 am Branko Vukelic wrote:
> On Wed, Jun 23, Philip Rhoades wrote:
>> What is going on with these size increases?
> It may be that after rotation, pixels that were
> otherwise the same color got anti-aliased and were
> slightly different color. This would increase the
> image size.

Branco, that may account for the increased size of a
_rotated_ image, but Phil also increased the size simply
during a re-save of an unchanged image.

Phil, I suspect that when re-saving that image, you may
wish to check the Advanced Settings popup to ensure that
the PNG compression ratio is set to maximum at the time.

WRT the rotated image, it wouldn't so much be anti-
aliasing as that the rotation is unlikely to be precisely
right-angled, so pixels along edges would be partially
coloured, which would make the PNG compression process
less efficient.

If the image is text or something else essentially
monochrome, Phil might try desaturating, then (regardless
of desat) Auto/Stretch Contrast. This should minimise
colour-gradient effects somewhat, so provide for more
effective compression.

If minute details are not so important, saving as JPeG
will reduce the size massively without serious loss of
visual quality. Loss of quality can be adjusted to a
reasonable compromise level within the JPeG settings
during SaveAs.

Cheers; Leon
Gimp-user mailing list

Reply via email to