Color distortion still

[Abe Gillespie]

Thanks Bart.  Increasing the output quality not only fixed the coloring
issue but another one I was having.  Thanks for the tip!  And I'll get
to filing the bug sometime today.

-Abe

On Jan 3, 2005, at 9:29 AM, Bart van den Eijnden wrote:

> Hi Abe,
>
>> 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?
>
> Filing a bug is done through the Mapserver bugzilla.
>
> http://mapserver.gis.umn.edu/bugs/
>
> First you need to register in order to being able to file a bug, you
> can
> do this by following the link: "Open a new Bugzilla account".
>
> The bugzilla system is quite easy to follow, so I am sure you will
> manage.
> One of the most important things is to add an attachment to the bug,
> which
> can only be done after the bug has been submitted (there is a link then
> called "create an attachment" or something similar).
>
>> Also, what do I need to do to change my image to a higher quality?
>
> You have to use RGBA imagemode instead of PC256, for instance for png
> use:
>
>   OUTPUTFORMAT
>     NAME png
>     MIMETYPE image/png
>     DRIVER GD/PNG
>     EXTENSION png
>     IMAGEMODE RGBA
>     TRANSPARENT TRUE
>   END
>
> Please note this will increase color depth to 24 bit instead of 8 bit,
> which will make the file size of the images larger.
>
> Best regards,
> Bart
>
>>
>> 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
>>>
>>
>