In other words, this has nothing to do with PNG

This one seems to work OK:
((TextStyle defaultFont characterFormAt: $T) magnifyBy: 16) asMorph openInWorld

This one is transparent:
((TextStyle defaultFont characterFormAt: $T) magnifyBy: 16) asMorph
imageForm asMorph openInWorld

Nicolas

2011/4/29 Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:
> 2011/4/29 Juan Vuletich <juan at jvuletich.org>:
>> Nicolas Cellier wrote:
>>>
>>> This code seems to work:
>>>    PNGReadWriter
>>>        putForm: ((TextStyle defaultFont characterFormAt: $T) magnifyBy:
>>> 16)
>>>        onFileNamed: 'T1.png'.
>>>
>>> This one produces a fully transparent image (at least in mac finder
>>> and firefox renderers):
>>>    PNGReadWriter
>>>        putForm: ((TextStyle defaultFont characterFormAt: $T)
>>> magnifyBy: 16) asMorph imageForm
>>>        onFileNamed: 'T2.png'.
>>>
>>> Though a FileList is able to display a preview of the image for both
>>> files,
>>> importing with:
>>>    Form openImageInWindow: (FileDirectory default / 'T2.png') fullName.
>>> just leave a transparent image in upper corner...
>>>
>>> While
>>>    Form openImageInWindow: (FileDirectory default / 'T1.png') fullName.
>>> works as expected...
>>>
>>> Any clue ?
>>>
>>> Nicolas
>>>
>>
>> Hi Nicolas,
>>
>> It is a bug in BitBlt. For instance:
>>
>>   | f f2 blt sourceDepth |
>>   sourceDepth := 16.
>>   f := Form extent: 16 at 16 depth: sourceDepth.
>>   f fillWhite.
>>   f2 := Form extent: 16 at 16 depth: 32.
>>   f2 fillColor: Color blue.
>>   blt := BitBlt new.
>>   blt setDestForm: f2 sourceForm: f fillColor: nil combinationRule: Form
>> paint destOrigin: 0 at 0 sourceOrigin: 0 at 0 extent: 16 at 16 clipRect: f
>> boundingBox.
>>   blt copyBits.
>>   f2 colorAt: 0 at 0
>>
>> prints 'Color transparent' if sourceDepth = 16, but 'Color white' if
>> sourceDepth = 32.
>>
>> The problem seems to be in BitBltSimulation>>#rgbMapPixel:flags:, if I
>> replace the last line with
>>
>>   val :=val bitOr: ((255) bitShift: (24)).
>>   ^val
>>
>> and call #copyBitsSimulated (with VMMaker loaded) It seems to work ok. This
>> is just a hack for testing, as it doesn't take into account actual source
>> and destination depths...
>>
>> Cheers,
>> Juan Vuletich
>>
>>
>
> Hi Juan,
> this was hard to understand because I didn't noticed that imageFrom
> was doing the 16bits -> 32bits copy...
> But now I get it, thanks.
>
> Nicolas
>