Support for loading 32bit images (convert alpha to transparent)

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Basically need to :
Have a settable threshhold for alpha, for example 128: less transparent is 
kept, more transparent is ignored (color won't count when determining target 
palette).
Palette needs be reduced to 255 (not 256), and transparent pixels must be set 
to the reserved index.
A sample image is attached : ratimbum.png by Jinn 
(http://www.pixeljoint.com/pixelart/53309.htm)
It has large colored areas 'hidden' by alpha=0. The card figures also have an 
alpha level of about 50%.

Original issue reported on code.google.com by yrizoud on 16 Jun 2010 at 2:57

Attachments:

• ratimbum.png

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Original comment by pulkoma...@gmail.com on 9 Aug 2010 at 9:46

• Added labels: Component-Files

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Original comment by pulkoma...@gmail.com on 10 Apr 2011 at 8:43

• Added labels: Milestone-2.4

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Arbitering issues that make it to v2.4

Original comment by yrizoud on 8 Mar 2012 at 7:18

• Added labels: Milestone-2.5