[VM][BUG] losing alpha channel
Lex Spoon
lex at cc.gatech.edu
Mon Jun 2 08:31:50 UTC 2003
asFormOfDepth: doesn't fixup the alpha chanel on conversion from 16 bits
to 32 bits. Similarly, drawing a 16-bit form onto a Form using a
FormCanvas has the same problem. Conversion from 8 bits to 32 bits has
no trouble.
What's up? I notice a method called fixAlpha:with: with a very
suggestive comment, but I don't know how to use it. I post this in the
hopes someone can suggest a one-line fix, before I delve deeper.
My image is 3.5-5174 , though non-standard changes may well have crept
in
My VM is Ian's 3.4 release
Lex
=====
form0 := ImageReadWriter formFromStream: 'http://www.squeakland.org/images/logo.jpg' asUrl retrieveContents contentStream.
form32 := form0 asFormOfDepth: 32.
form32 colorAt: 50 at 50 "transparent!!"
form32 := (Form extent: form0 extent depth: 32).
(FormCanvas on: form32) drawImage: form0 at: 1 at 1.
form32 colorAt: 50 at 50 "also transparent"
form32 := (form0 asFormOfDepth: 8) asFormOfDepth: 32.
form32 colorAt: 50 at 50 "this is fine -- the problem seems peculiar to 16->32 conversions"
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