Bad colors with mapserver

[Trond Michelsen]

On Thu, Nov 24, 2005 at 12:37:14PM -0700, Sean Gillies wrote:
> On Nov 24, 2005, at 11:36 AM, Trond Michelsen wrote:
>> On Thu, Nov 24, 2005 at 09:08:54AM -0800, Tyler Mitchell wrote:
>>>>  name           klimawms
>>>>  imagetype      png
>>> Hi Trond,
>>> Trying changing imagetype to PNG24...
>> Hmm. I've tried setting imagetype to "png24" without success. But I
>> can try "PNG24" as well.  It'll have to wait until tomorrow, though.
> Sounds like you've used up all 256 colors in the standard 8-bit PNG  
> palette. If JPEG looks OK, then 24-bit PNG should be OK too.

> One of the most common causes is anti-aliased freetype fonts. Your  
> font color may be black, so you figure one color, right? Well, if you  
> look at your image closely, you'll see that black text rendered with  
> anti aliasing over a blue polygon actually uses 12+ colors. In the  
> same map, you'll also have text over green polygons, red polygons,  
> with another 12+ colors for each. It adds up quick. Using pixmap  
> symbols can also eat up big chunks of color space in your output image.

Doh!

I can't believe I forgot about anti-aliasing. The text and logoes
aren't even supposed to be there. I was thinking of just creating a
shape-file which covers all tekst and logoes, but I suppose it's
better to ask for a set of pictures with nothing but the map.

I'll have a look at that tomorrow. Thanks.
 
> If you have to use an 8-bit indexed color PNG, you can reserve  
> important colors by drawing layers with that color early. All you  
> have to do is draw a single point or line.

Nice to know. Thanks.

-- 
Trond Michelsen