PDL image to SDL::Surface

[Tobias Leich]

Hi, Andrei asked some days ago how to load an image via PDL and but it
in a Surface to use it in SDL.

The example is here: https://gist.github.com/3772701

I'll put that in the examples folder too.

Cheers, Tobias

[Chris Marshall]

I took a look at the gist and it looks reasonable
(I can't run it because I don't have the SDL module
and lib installed on my system), however...

I would expect the performance to be *very* poor
since the image data is essentially being converted
from packed byte data to a perl list and then poked
a byte at a time into the SDL surface data.

The better approach would be to wrap a PDL object
(a.k.a. piddle) into an SDL surface. Then you could
just lock, copy the data via a PDL direct assignment,
unlock and use SDL. There is an examples/pdl.pl
that shows how to do the wrapping.

BUT, I took a look at the xs code and it appears
that your SDL_Surface objects no longer use a
packed-string representation for the SDL surface
data. If that is the case, I would be surprised if
the pdl.pl example works at all now.

If someone could verify this, I would appreciate it.
If that is the case, it should be straightforward to
modify the SDL_CreateRGBSurfaceFrom routine
to allow for a SvPV for pixel data as one alternative.

Given the power of PDL for whole-image data
manipulation, allowing for easy interoperability
with the current SDL module would benefit both
our user and developer communities.

Regards,
Chris

[Tobias Leich]

Hi Chris,

The performance is poor of course.

I tried to use the piddels pointer (->dataref or so) but it looks like
it is not pointing to a usable memory area.
It looks like there are more than 4 bytes per pixel, and libSDL can't
handle that.

The pdl.pl example is working, I see colored squares.

I think we should need to improve our examples btw, there is not a
single comment, thats bad.
In the pdl.pl is a var $ref, which is never used. Thats a bit confusing.

Cheers, Tobias

[Chris Marshall]

On Mon, Sep 24, 2012 at 10:41 AM, Tobias Leich <em...@froggs.de> wrote:
> Hi Chris,
>
> The performance is poor of course.
>

> I tried to use the piddle's pointer (->dataref or so) but it looks like

> it is not pointing to a usable memory area.

$piddle->get_dataref returns a scalar reference to a perl
PV whose string content _is_ the data block. You should
be able to get the starting location for the pixel data (i.e.,
the string) via SvPV.

> It looks like there are more than 4 bytes per pixel, and libSDL can't
> handle that.

Per the above, the get_dataref returns an RV to an Sv with
the data in the string. It is just a contiguous block of memory.
As far as I know, all the SDL memory buffers are just
contiguous blocks of memory (ignoring variations due to
stride, alignment,...)

> The pdl.pl example is working, I see colored squares.

I don't know what the output should look like. I'm
cc-ing our PDL mailing list in the hopes that someone
with access to both PDL and SDL can give it a try.

Is there a cygwin install of SDL and libSDL?

> I think we should need to improve our examples btw, there is not a
> single comment, thats bad.
> In the pdl.pl is a var $ref, which is never used. Thats a bit confusing.

I think the ref is from a previous iteration in the code
trying to get things working.

Speaking of documentation, do you have any on the
actual perl<->libSDL bindings an data structures? Trying
to read XS is not the simplest way to sort things out---
especially since I am far for an expert on some of the
tricky XS technologies.

--Chris

[Tobias Leich]

Am 24.09.2012 18:07, schrieb Chris Marshall:
> On Mon, Sep 24, 2012 at 10:41 AM, Tobias Leich <em...@froggs.de> wrote:
>> Hi Chris,
>>
>> The performance is poor of course.
>>
>> I tried to use the piddle's pointer (->dataref or so) but it looks like
>> it is not pointing to a usable memory area.
> $piddle->get_dataref returns a scalar reference to a perl
> PV whose string content _is_ the data block. You should
> be able to get the starting location for the pixel data (i.e.,
> the string) via SvPV.

Okay, so we need to change the Surface's XS code to accept that.

>
>> It looks like there are more than 4 bytes per pixel, and libSDL can't
>> handle that.
> Per the above, the get_dataref returns an RV to an Sv with
> the data in the string. It is just a contiguous block of memory.
> As far as I know, all the SDL memory buffers are just
> contiguous blocks of memory (ignoring variations due to
> stride, alignment,...)

The memory block is not the point. It matters how the pixels are stored
in that block.
LibSDL can use 1 to 4 bytes per Pixel. And we can tell it how a pixel
looks like. If it is RGB or RGBA or ABGR or whatever.
But it is important to know how the pixels are stored, since otherwise
it might use the alpha channel for the red color.

>> The pdl.pl example is working, I see colored squares.
> I don't know what the output should look like. I'm
> cc-ing our PDL mailing list in the hopes that someone
> with access to both PDL and SDL can give it a try.
>
> Is there a cygwin install of SDL and libSDL?

I'm afraid that cygwin support is currently half-broken. If you would
install only the libSDL core components and no SDL_ttf stuff you might
get a chance to install SDL-perl.

>
>> I think we should need to improve our examples btw, there is not a
>> single comment, thats bad.
>> In the pdl.pl is a var $ref, which is never used. Thats a bit confusing.
> I think the ref is from a previous iteration in the code
> trying to get things working.
>
> Speaking of documentation, do you have any on the
> actual perl<->libSDL bindings an data structures? Trying
> to read XS is not the simplest way to sort things out---
> especially since I am far for an expert on some of the
> tricky XS technologies.

Of course. for example:
http://sdl.perl.org/documentation.html
http://search.cpan.org/~jtpalmer/SDL-2.540/
https://github.com/PerlGameDev/SDL/tree/master/lib/pods

[Chris Marshall]

Looking back through the code to the original SDL_Perl
I found version 2.0.5 which allows one to actually create
an SDL surface from pixel data. More recent versions
appear to copy the data and as far as I can tell, there is
no way to directly create an SDL surface from external
data.

If that is the case (that SDL_CreateRGBSurfaceFrom is
not accessible from the perl API), have you implemented
another approach to achieve this?

Regards,
Chris

[Kartik Thakore]

Whats wrong with
https://github.com/PerlGameDev/SDL_Manual/blob/master/code_listings/pdl.pl ?

[Chris Marshall]

PDL supports arbitrary numbers of dimensions of
data. All that we need to know is how SDL is treating
the data so that an equivalent mapping is set up for
processing on the PDL side.

>> Speaking of documentation, do you have any on the
>> actual perl<->libSDL bindings an data structures? Trying
>> to read XS is not the simplest way to sort things out---
>> especially since I am far for an expert on some of the
>> tricky XS technologies.

Thanks for the refs. --Chris

[Chris Marshall]

Hi Kartik-

I don't have a working SDL module install that I could
check things out on. The posted gist seemed like a
regression of using direct PDL manipulation to read and
copy the image data to an SDL surface.

The pdl.pl example seemed ok to me until I tried looking
at the latest XS code where it seemed that the SDL module
doesn't not accept a packed string data as input to the
"surface from" routines.

--Chris

[Sisyphus]

----- Original Message -----
From: "Chris Marshall" <devel....@gmail.com>
To: "Kartik Thakore" <thakore...@gmail.com>
Cc: "Tobias Leich" <em...@froggs.de>; "sdl-devel" <sdl-...@perl.org>
Sent: Tuesday, September 25, 2012 2:46 AM
Subject: Re: [Perldl] PDL image to SDL::Surface


> Hi Kartik-
>
> I don't have a working SDL module install that I could
> check things out on.

Hi guys,

Chris, 'cpan -fi SDL' should install SDL-2.54 on your SPP. (You need force
because a couple of the SDL tests fail.)
During the 'perl build.pl' stage of Alien::SDL you'll be prompted to select
which library package to install. I took option 1 because it was
"RECOMMENDED", though option 2 is probably more recent.

I've run the demo at https://gist.github.com/3772701 but that just produces:

C:\_32\pscrpt\pdl>perl pdl2surface.pl
No available video device at C:/_32/strawberry516/perl/site/lib/SDLx/App.pm
line 123, <DATA> line 206.
SDLx::App::new('SDLx::App', 'title', 'PDL and SDL aplication', 'width', 640,
'height', 640, 'eoq', 1, ...) called at pdl2surface.pl line 12

And same error for
https://github.com/PerlGameDev/SDL_Manual/blob/master/code_listings/pdl.pl

I don't know what needs to be done in order that a "video device" becomes
available. (I'm probably not the sharpest tool in the shed to be using for
this ;-)

Cheers,
Rob

[Kartik Thakore]

Can you select a videodriver for SDL by exporting SDL_VIDEODRIVER
either fbcon or x11 may fix this. If not then your SDL were not compiled
with X11 libs. Install those.

On Mon, Sep 24, 2012 at 6:36 PM, Sisyphus <sisy...@optusnet.com.au> wrote:

>
> ----- Original Message ----- From: "Chris Marshall" <
> devel....@gmail.com>
> To: "Kartik Thakore" <thakore...@gmail.com>
> Cc: "Tobias Leich" <em...@froggs.de>; "sdl-devel" <sdl-...@perl.org>
> Sent: Tuesday, September 25, 2012 2:46 AM
> Subject: Re: [Perldl] PDL image to SDL::Surface
>
>
>
> Hi Kartik-
>>
>> I don't have a working SDL module install that I could
>> check things out on.
>>
>
> Hi guys,
>
> Chris, 'cpan -fi SDL' should install SDL-2.54 on your SPP. (You need force
> because a couple of the SDL tests fail.)
> During the 'perl build.pl' stage of Alien::SDL you'll be prompted to
> select which library package to install. I took option 1 because it was
> "RECOMMENDED", though option 2 is probably more recent.
>

> I've run the demo at https://gist.github.com/**3772701<https://gist.github.com/3772701>but that just produces:

>
> C:\_32\pscrpt\pdl>perl pdl2surface.pl

> No available video device at C:/_32/strawberry516/perl/**site/lib/SDLx/App.pm

> line 123, <DATA> line 206.
> SDLx::App::new('SDLx::App', 'title', 'PDL and SDL aplication', 'width',
> 640, 'height', 640, 'eoq', 1, ...) called at pdl2surface.pl line 12
>
> And same error for

> https://github.com/**PerlGameDev/SDL_Manual/blob/**
> master/code_listings/pdl.pl<https://github.com/PerlGameDev/SDL_Manual/blob/master/code_listings/pdl.pl>

[Chris Marshall]

This was for Strawberry Perl on windows so the
device should be whatever the default is for windows.
If it needs X11, then the build probably did not
configure correctly for the platform. It looks like
libSDL does support windows and MinGW and
the docs do not indicate that X11 is a prerequisite
for that.

--Chris

On Mon, Sep 24, 2012 at 7:03 PM, Kartik Thakore
<thakore...@gmail.com> wrote:
> Can you select a videodriver for SDL by exporting SDL_VIDEODRIVER
> either fbcon or x11 may fix this. If not then your SDL were not compiled
> with X11 libs. Install those.
>
>
> On Mon, Sep 24, 2012 at 6:36 PM, Sisyphus <sisy...@optusnet.com.au> wrote:
>>
>>
>> ----- Original Message ----- From: "Chris Marshall"
>> <devel....@gmail.com>
>> To: "Kartik Thakore" <thakore...@gmail.com>
>> Cc: "Tobias Leich" <em...@froggs.de>; "sdl-devel" <sdl-...@perl.org>
>> Sent: Tuesday, September 25, 2012 2:46 AM
>> Subject: Re: [Perldl] PDL image to SDL::Surface
>>
>>
>>
>>> Hi Kartik-
>>>
>>> I don't have a working SDL module install that I could
>>> check things out on.
>>
>>
>> Hi guys,
>>
>> Chris, 'cpan -fi SDL' should install SDL-2.54 on your SPP. (You need force
>> because a couple of the SDL tests fail.)
>> During the 'perl build.pl' stage of Alien::SDL you'll be prompted to
>> select which library package to install. I took option 1 because it was
>> "RECOMMENDED", though option 2 is probably more recent.
>>

>> I've run the demo at https://gist.github.com/3772701 but that just

>> produces:
>>
>> C:\_32\pscrpt\pdl>perl pdl2surface.pl
>> No available video device at

>> C:/_32/strawberry516/perl/site/lib/SDLx/App.pm line 123, <DATA> line 206.

>> SDLx::App::new('SDLx::App', 'title', 'PDL and SDL aplication', 'width',
>> 640, 'height', 640, 'eoq', 1, ...) called at pdl2surface.pl line 12
>>
>> And same error for

[Tobias Leich]

There prebuilt binaries for windows that you can choose when installing
Alien::SDL. There is no choice to build libsdl yourself on that platform.
And I never heard of that error before.

On what type of windows are you exactly? WinXP 32bit?

[Chris Marshall]

On Mon, Sep 24, 2012 at 12:46 PM, Chris Marshall <devel....@gmail.com> wrote:
> Hi Kartik-
>
> I don't have a working SDL module install that I could
> check things out on. The posted gist seemed like a
> regression of using direct PDL manipulation to read and
> copy the image data to an SDL surface.
>
> The pdl.pl example seemed ok to me until I tried looking
> at the latest XS code where it seemed that the SDL module
> doesn't not accept a packed string data as input to the
> "surface from" routines.

Still don't have an SDL install but reviewing objects/Surface.xs
a bit more it appears that the ->get_pixels_ptr() does return a
scalar perl reference to a PV with the string pointer being the
pointer to the pixel data.

However, the ->new_from() method appears to assume the
pixel pointer is actually poked into the RV slot of the dereferenced
SV rather than the PV string. This seems inconsistent.