[Vm-dev] JPEGReadWriter2Plugin

[David T. Lewis]

I think that John made some changes that would have entered the VMMaker updates
as of VMMaker-JMM.166 (March 2010). In addition, three methods are different
between the Cog branch and the main branch:

	#primJPEGReadHeader:fromByteArray:errorMgr:
	#primJPEGReadImage:fromByteArray:onForm:doDithering:errorMgr:
	#primJPEGWriteImage:onByteArray:form:quality:progressiveJPEG:errorMgr:

Looking at the method time stamps I'm guessing that there was some fix
made by Andreas in 2006 that is present in the Cog code base but not
the main VMMaker. My guess would be that we should be using the Cog
versions, and merging John's March 2010 updates into this.

I just happen to be part way through converting the plugins to use
pragmas to match Cog. The updates for primitives should be done in
a couple of days, after which it will be easier to spot differences
like this.

Dave


On Mon, Sep 27, 2010 at 05:22:43PM +0200, Bert Freudenberg wrote:
> 
> Hi,
> 
> have there been changes lately to the jpeg plugin?
> 
> On a Mac 4.2.4 VM I see an off-by-one error, all pixels are moved to the right, the first pixel is transparent. On a Mac 5.8.1 Cog VM it works as expected though.
> 
> Here's my little test:
> 
> (JPEGReadWriter2 formFromStream: #[16rFF 16rD8 16rFF 16rE0 16r00 16r10 16r4A 16r46 16r49 16r46 16r00 16r01 16r01 16r01 16r00 16r48 16r00 16r48 16r00 16r00 16rFF 16rDB 16r00 16r43 16r00 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rC2 16r00 16r0B 16r08 16r00 16r01 16r00 16r01 16r01 16r01 16r11 16r00 16rFF 16rC4 16r00 16r14 16r10 16r01 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16r00 16rFF 16rDA 16r00 16r08 16r01 16r01 16r00 16r01 16r3F 16r10] readStream) bits first hex
> 
> On 5.8.11 I get 16rFF808080 as expected, on 4.2.4 I get 0.
> 
> - Bert -
>