low quality image output

[Frank Warmerdam]

On 10/12/05, Richard Alexander <raxpl at anglesey.gov.uk> wrote:
> hi list,
> I've seen a few other entries with a similar problem relating to jpeg
> outputs...mine relates to jpeg, tif, png, bmp: when accessing a 800kbyte
> aerial image (via world file & mapscript) the output image gets
> reconstructed to a very "blocky" output with few colours - tried playing
> around with imagemodes (e.g. MS_IMAGEMODE_RGB) but no improvement  - I've
> noticed a difference  in rendering using a tif source, but it's not better,
> just slightly different. thanks for any assistance.
> (just as a check i've opened the same image using PIL on it's own and it's
> up there with the best of them !)

Richard,

I would be interested in seeing the LAYER definition you use,
as well as the gdalinfo report on the input file and your IMAGETYPE
and OUTPUTFORMAT declarations.  Can you also supply a rendered
result we could review to see the effect you mean?

Normally the poor color quality issues only come up with converting
to 8bit pseudocolored.  But if you are really rendering to jpeg or
png24 then that should not be an issue.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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