First lets get the right modules.
Suppose you want a surface of size (200,400) and 32 bit (RGBA).
my ( $bytes_per_pixel, $width, $height ) = ( 4, 200, 400 );
Define the $width, $height and $bytes_per_pixel. Your $bytes_per_pixel is the number of bits (in this case 32) divided by 8 bits per byte. Therefore for our 32 bpp we have 4 Bpp;
my $piddle = zeros( byte, $bytes_per_pixel, $width, $height );
Create a normal $piddle with zeros, byte format and the Bpp x width x height dimensions.
my $pointer = $piddle->get_dataref();
Here is where we get the actual data the piddle is pointing to. We will have SDL create a new surface from this function.
my $surface = SDL::Surface->new_from( $pointer, $width, $height, 32,
$width * $bytes_per_pixel );
Using the same dimensions we create the surface using new_form. The width * Bpp is the scanline (pitch) of the surface in bytes.
warn "Made surface of $width, $height and ". $surface->format->BytesPerPixel;
return ( $piddle, $surface );
Finally make sure that the surface actually has the correct dimensions we gave.
<B>NOTE:B> $surface->format->BytesPerPixel must return 1,2,3,4. !!
Now you can blit and use the surface as needed; and do PDL operations as required.
To make sure SDL is in sync with the data. You must call SDL::Video::lock <B>beforeB> doing PDL operations on the piddle.
$piddle->mslice( X, [ rand(400), rand(400), 1 ], [ rand(200), rand(200), 1 ] )
.= pdl( rand(225), rand(225), rand(255), 255 );
After that you can unlock the surface to blit.
When blitting the new surface check for the return value to see if there has been a problem.
my $b = SDL::Video::blit_surface(
$surface, SDL::Rect->new( 0, 0, $surface->w, $surface->h ),
$app, SDL::Rect->new( ( $app->w - $surface->w ) / 2, ( $app->h - $surface->h ) / 2, $app->w, $app->h )
die "Could not blit: " . SDL::get_error() if ( $b == -1 );
If the error message is Blit combination not supported that means that the BPP is incorrect or inconsistent with the dimensions.
After that a simple update_rect will so your new surface on the screen.