new PNGReadWriter with libpng support

Andreas Raab andreas.raab at
Wed Nov 22 17:59:20 UTC 2006

Jens Lincke wrote:
> I made a PNGReadWriter2 and a PNGReadWriter2Plugin with libpng support 
> for fast png reading, which is needed in Sophie and future versions of 
> Plopp.
> Currently it can only read a png file and returns only 32bit forms.
> The repository for this is

All I find in there is

PNGReadWriter2>>primPNGReadImageFromByteArray: source onForm: form
	self primitiveFailed

PNGReadWriter2>>primPNGReadInfoFromByteArray: source onForm: form
	self primitiveFailed

> and I build it with vmaker 3.8b6, squeak 3.9 and the squeak 3.9-8 unix 
> sources.

I'm a little confused to see statements like here in the plugin:

    formPix isNil ifTrue: [formPix := 1].

this should be translated to isNil(formPix) and as far as I am aware 
there is no such function available anywhere. Also, it seems as if there 
are some serious hazards for decoding the PNG data - the code doesn't 
set a limit for the source of input when decoding so I presume libpng 
will simply fall over and break (possibly corrupting Squeak memory) if 
you give it partial input?

   - Andreas

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