2011/4/29 Juan Vuletich juan@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@16 depth: sourceDepth.   f fillWhite.   f2 := Form extent: 16@16 depth: 32.   f2 fillColor: Color blue.   blt := BitBlt new.   blt setDestForm: f2 sourceForm: f fillColor: nil combinationRule: Form paint destOrigin: 0@0 sourceOrigin: 0@0 extent: 16@16 clipRect: f boundingBox.   blt copyBits.   f2 colorAt: 0@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

Anyway, it's an old and known bug with known workaround, see senders of #fixAlpha

Nicolas

2011/4/29 Nicolas Cellier nicolas.cellier.aka.nice@gmail.com:

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@gmail.com:

...

2011/4/29 Juan Vuletich juan@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@16 depth: sourceDepth.   f fillWhite.   f2 := Form extent: 16@16 depth: 32.   f2 fillColor: Color blue.   blt := BitBlt new.   blt setDestForm: f2 sourceForm: f fillColor: nil combinationRule: Form paint destOrigin: 0@0 sourceOrigin: 0@0 extent: 16@16 clipRect: f boundingBox.   blt copyBits.   f2 colorAt: 0@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