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.\"
.IX Title "pods::SDL::Cookbook::PDL 3pm"
.TH pods::SDL::Cookbook::PDL 3pm "2020-11-09" "perl v5.32.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
SDL::CookBook::PDL \-\- CookBook for SDL + PDL
.PP
PDL provides great number crunching capabilities to Perl and SDL provides game\-developer quality real\-time bitmapping and sound.  You can use PDL and SDL ''together'' to create real\-time, responsive animations and simulations.  In this section we will go through the pleasures and pitfalls of working with both powerhouse libraries.
.SS "\s-1CATEGORY\s0"
.IX Subsection "CATEGORY"
Cookbook
.SH "Creating a SDL Surface piddle"
.IX Header "Creating a SDL Surface piddle"
\&\s-1PDL\s0's core type is a piddle. Once a piddle is provided to \s-1PDL\s0 it can go do a numerous amounts of things. Please see the example in 'examples/cookbook/pdl.pl' that came with this module.
.SS "Creating a simple piddle"
.IX Subsection "Creating a simple piddle"
First lets get the right modules.
.PP
.Vb 5
\&  use PDL;
\&  use SDL::Rect;
\&  use SDL::Video;
\&  use SDL::Surface;
\&  use SDL::PixelFormat;
.Ve
.PP
Suppose you want a surface of size (200,400) and 32 bit (\s-1RGBA\s0).
.PP
.Vb 1
\&   my ( $bytes_per_pixel, $width, $height ) = ( 4, 200, 400 );
.Ve
.PP
Define the \f(CW$width\fR, \f(CW$height\fR and \f(CW$bytes_per_pixel\fR. Your \f(CW$bytes_per_pixel\fR is the number of bits (in this case 32) divided by 8 bits per byte. Therefore for our 32 bpp we have 4 Bpp;
.PP
.Vb 1
\&   my $piddle  = zeros( byte, $bytes_per_pixel, $width, $height );
.Ve
.PP
Create a normal \f(CW$piddle\fR with zeros, byte format and the Bpp x width x height dimensions.
.PP
.Vb 1
\&   my $pointer = $piddle\->get_dataref();
.Ve
.PP
Here is where we get the actual data the piddle is pointing to. We will have \s-1SDL\s0 create a new surface from this function.
.PP
.Vb 2
\&   my $surface = SDL::Surface\->new_from( $pointer, $width, $height, 32,
\&        $width * $bytes_per_pixel );
.Ve
.PP
Using the same dimensions we create the surface using new_form. The width *  Bpp is the scanline (pitch) of the surface in bytes.
.PP
.Vb 2
\&   warn "Made surface of $width, $height and ". $surface\->format\->BytesPerPixel;
\&   return ( $piddle, $surface );
.Ve
.PP
Finally make sure that the surface actually has the correct dimensions we gave.
.PP
\&\fB\s-1NOTE:\s0\fR \f(CW$surface\fR\->format\->BytesPerPixel must return 1,2,3,4. !!
.PP
Now you can blit and use the surface as needed; and do \s-1PDL\s0 operations as required.
.SS "Operating on the Surface safely"
.IX Subsection "Operating on the Surface safely"
To make sure \s-1SDL\s0 is in sync with the data. You must call SDL::Video::lock \fBbefore\fR doing \s-1PDL\s0 operations on the piddle.
.PP
.Vb 1
\&    SDL::Video::lock_surface($surface);
\&
\&    $piddle\->mslice( \*(AqX\*(Aq, [ rand(400), rand(400), 1 ], [ rand(200), rand(200), 1 ] )
\&        .= pdl( rand(225), rand(225), rand(255), 255 );
.Ve
.PP
After that you can unlock the surface to blit.
.PP
.Vb 1
\&    SDL::Video::unlock_surface($surface);
.Ve
.SS "Error due to \s-1BPP\s0 at blitting"
.IX Subsection "Error due to BPP at blitting"
When blitting the new surface check for the return value to see if there has been a problem.
.PP
.Vb 4
\&    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 );
.Ve
.PP
If the error message is 'Blit combination not supported' that means that the \s-1BPP\s0 is incorrect or inconsistent with the dimensions.
After that a simple update_rect will so your new surface on the screen.
.SH "AUTHORS"
.IX Header "AUTHORS"
See \*(L"\s-1AUTHORS\*(R"\s0 in \s-1SDL\s0.