Color distortion still

[Abe Gillespie]

I have yet to file a bug but would be happy to do so.  Would you mind
pointing me to some info on how to get started?

Also, what do I need to do to change my image to a higher quality?

Thanks.
-Abe

On Jan 3, 2005, at 9:07 AM, Frank Warmerdam wrote:

> On Mon, 3 Jan 2005 09:01:44 -0500, Abe Gillespie <agillesp at vt.edu>
> wrote:
>> I'm using the latest version but am still getting color changing
>> problems.  Now, however, it only happens when I have a layer with
>> transparency.  You can see the problems here:
>>
>> layer w/o transparency:
>> http://141.152.79.120/temp/color.png
>>
>> layer w/ transparency:
>> http://141.152.79.120/temp/grey.png
>>
>> The layer with the transparency I change is the one that goes from a
>> pinkish color to grey.
>
> Abe,
>
> I have reviewed the gdImageCopyMerge() used by mapserver
> to apply transparent layers to the master copy, and the problem
> seems to be there.  It appears it deliberately uses only a greyscale
> value from the layer being overlaid on the master, presumably to
> moderate the number of colors used.
>
> Generally speaking I would advise against using transparent
> layers in 8bit mode anyways due to the difficult to predict number
> of colors that will be needed.
>
> The gdImageCopyMerge() function is a part of the GD library and
> so not under out (the mapserver developers) direct control.
> However, if you want to file a bug on the problem we could try
> and incorporate a special case in our higher level logic to handle
> transparency with 8bit (pseudocolored) images.  If you file a bug on
> this issue please include this email so we don't have to re-discover
> what is going on.
>
> Best regards,
> --
> ---------------------------------------
> +--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>