[udig-devel] export map to image bug

[Graham Davis <gdavis@xxxxxxxxxxxxxxx>]

I'm working on fixing a bug where exporting a map to image to a 
non-alpha image format (ie: jpeg) results in an image with a weird 
background colour.  I've narrowed down the problem to the creation of 
the bufferedImage creation in ExportMapToImageWizard.java:

BufferedImage image = new BufferedImage(width, height, 
BufferedImage.TYPE_INT_ARGB);

This line works fine for images being exported to formats that support 
alpha (like png).  If I change the type in the above line to 
TYPE_INT_RGB it works for all image formats.  I'm assuming it is alright 
to fix this bug by simply changing that?  Are there any reasons that a 
png or other format would need to be saved from a bufferedImage with 
alpha support?  The resulting image (as far as I can tell) is always 
just a composite built up from all the map layers into a single image 
anyways.

Initially I was trying to determine a way to use a different 
bufferedImage type depending on if the image format it will eventually 
be saved to supports alpha, but I couldn't figure out a way to easily 
determine that short of making my own long list of all known formats and 
if they support alpha.  I didn't think this was the best solution since 
that list could change or need updating.  Is there any system built into 
uDig that can already tell what image formats support alpha or not?  If 
not, is simply changing the above type to RGB instead of ARGB an 
acceptable fix for this bug?  Thanks,

--
Graham Davis
Refractions Research Inc.
gdavis@xxxxxxxxxxxxxxx