>> JPEG is lossy and intended as such. GIF and PNG are nor lossy
>> but do not
>> provide the compression ratios possible with JPEG.
> This is not strictly true. JPEG only provides good lossy compression if the
> image is of a photographic origin. Also, certain photographs do not
> compress well with JPEG.
I think the term 'compress well' needs clarification.
1. JPEG will successfully reduce file-size to specification... This is not
significantly
affected by image content.
2. JPEG will provide differing image-qualities at the same compression levels for
images of different content.
3. JPEG can compress image drawn from a paint program equally well as
photo-realistic images although the pixel structure that cause artifacting are
considerably more common in hand-drawn low palette-size images (number of colours
in images, NOT whether or not a palette is stored since JPEG does not work on
pallete based images).
> GIF and PNG on the other hand provides much better
> compression that JPEG with images drawn with a paint type program.
Where small palette sizes or large contiguous areas of the same (or similar) color are
evident... Usage of more powerful image manipulation software that handle smoothing,
antialiasing, alphablending and colour shifting for you will soon generate images that
do
not compress well in PNG and can't be stored in GIF... I would however suggest that PNG
is the best portable format to invest in for Loss-less and work-in-progress formats
(other
than the native format of your image software (eg PSD))...
--
Aaron Scott-Boddendijk
Jump Productions
(07) 838-3371 Voice
(07) 838-3372 Fax
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