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PixelPeeker plugin

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timrowledge

PixelPeeker plugin

One of the issues with doing Squeak/Scratch for the Pi is the rather dismal bitblt performance. I'm working on that with another colleague in the UK, but one interesting common case I've found in my tracing runs of Scratch is alot of use of pixelValueAt:, which builds a bitblt and runs it to move a single pixel and then look at it. That adds up to a lot of work for not much result so I've written a little plugin with (so far) a single prim to read a single pixel with rather less fiddling.

So far it only deals with Squeak internal format bitmps (ie demented spawn of satan big-endian not-at-all-like-RISC-OS structure) but does cope with 1/2/4/8/16/32 bpp ok. I could probably make it handle LSB (which is closer to convenient for almost all machines these days) and probably even external bitmaps if there is any real need.

Currently the code is all on its lonesome but I suppose it could be added to the bitblt plugin if that's a popular idea.
Included is a copy for anyone interested to try out and find bugs -

tim
--
tim Rowledge; [hidden email]; http://www.rowledge.org/tim
Strange OpCodes: IA: Illogical And

pixelpeeker.2.cs (6K) Download Attachment

Karl Ramberg

Re: PixelPeeker plugin

Cool

I have wished for something like this a long time

Karl

On Fri, Mar 15, 2013 at 7:27 PM, tim Rowledge <[hidden email]> wrote:

One of the issues with doing Squeak/Scratch for the Pi is the rather dismal bitblt performance. I'm working on that with another colleague in the UK, but one interesting common case I've found in my tracing runs of Scratch is alot of use of pixelValueAt:, which builds a bitblt and runs it to move a single pixel and then look at it. That adds up to a lot of work for not much result so I've written a little plugin with (so far) a single prim to read a single pixel with rather less fiddling.

So far it only deals with Squeak internal format bitmps (ie demented spawn of satan big-endian not-at-all-like-RISC-OS structure) but does cope with 1/2/4/8/16/32 bpp ok. I could probably make it handle LSB (which is closer to convenient for almost all machines these days) and probably even external bitmaps if there is any real need.

Currently the code is all on its lonesome but I suppose it could be added to the bitblt plugin if that's a popular idea.
Included is a copy for anyone interested to try out and find bugs -

tim
--
tim Rowledge; [hidden email]; http://www.rowledge.org/tim
Strange OpCodes: IA: Illogical And

Bert Freudenberg

Re: PixelPeeker plugin

In reply to this post by timrowledge

On 2013-03-15, at 19:27, tim Rowledge <[hidden email]> wrote:

> One of the issues with doing Squeak/Scratch for the Pi is the rather dismal bitblt performance. I'm working on that with another colleague in the UK, but one interesting common case I've found in my tracing runs of Scratch is alot of use of pixelValueAt:, which builds a bitblt and runs it to move a single pixel and then look at it. That adds up to a lot of work for not much result so I've written a little plugin with (so far) a single prim to read a single pixel with rather less fiddling.
>
> So far it only deals with Squeak internal format bitmps (ie demented spawn of satan big-endian not-at-all-like-RISC-OS structure) but does cope with 1/2/4/8/16/32 bpp ok.

BitBlt does do endian conversion for a while now, no? The platform code simply needs to answer negative depths for its supported displays.

> I could probably make it handle LSB (which is closer to convenient for almost all machines these days) and probably even external bitmaps if there is any real need.

Yes, it should be as general as BitBlt itself.

> Currently the code is all on its lonesome but I suppose it could be added to the bitblt plugin if that's a popular idea.

Makes sense to add to the bitblt plugin, yes.

- Bert -

David T. Lewis

Re: PixelPeeker plugin

On Fri, Mar 15, 2013 at 10:16:32PM +0100, Bert Freudenberg wrote:

>
> On 2013-03-15, at 19:27, tim Rowledge <[hidden email]> wrote:
>
> > One of the issues with doing Squeak/Scratch for the Pi is the rather dismal bitblt performance. I'm working on that with another colleague in the UK, but one interesting common case I've found in my tracing runs of Scratch is alot of use of pixelValueAt:, which builds a bitblt and runs it to move a single pixel and then look at it. That adds up to a lot of work for not much result so I've written a little plugin with (so far) a single prim to read a single pixel with rather less fiddling.
> >
> > So far it only deals with Squeak internal format bitmps (ie demented spawn of satan big-endian not-at-all-like-RISC-OS structure) but does cope with 1/2/4/8/16/32 bpp ok.
>
> BitBlt does do endian conversion for a while now, no? The platform code simply needs to answer negative depths for its supported displays.
>
> > I could probably make it handle LSB (which is closer to convenient for almost all machines these days) and probably even external bitmaps if there is any real need.
>
> Yes, it should be as general as BitBlt itself.
>
> > Currently the code is all on its lonesome but I suppose it could be added to the bitblt plugin if that's a popular idea.
>
>
> Makes sense to add to the bitblt plugin, yes.
>
> - Bert -

+1

Dave