3 <h3 id="TOP">Index</h3>
5 <ul><li><a href="#NAME">NAME</a>
6 <ul><li><a href="#CATEGORY">CATEGORY</a></li>
9 <li><a href="#Creating_a_SDL_Surface_piddle">Creating a SDL Surface piddle</a>
10 <ul><li><a href="#Creating_a_simple_piddle">Creating a simple piddle</a></li>
11 <li><a href="#Operating_on_the_Surface_safely">Operating on the Surface safely</a></li>
12 <li><a href="#Error_due_to_BPP_at_blitting">Error due to BPP at blitting</a>
19 <h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>
20 <div id="NAME_CONTENT">
21 <p>SDL::CookBook::PDL -- CookBook for SDL + PDL</p>
22 <p>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.</p>
29 <h2 id="CATEGORY">CATEGORY</h2>
30 <div id="CATEGORY_CONTENT">
34 <h1 id="Creating_a_SDL_Surface_piddle">Creating a SDL Surface piddle</h1><p><a href="#TOP" class="toplink">Top</a></p>
35 <div id="Creating_a_SDL_Surface_piddle_CONTEN">
36 <p>PDL's core type is a piddle. Once a piddle is provided to PDL it can go do a numerous amounts of things. Please see the example in 'examples/cookbook/pdl.pl' that came with this module.</p>
39 <h2 id="Creating_a_simple_piddle">Creating a simple piddle</h2>
40 <div id="Creating_a_simple_piddle_CONTENT">
41 <p>First lets get the right modules.</p>
49 <p>Suppose you want a surface of size (200,400) and 32 bit (RGBA).</p>
50 <pre> my ( $bytes_per_pixel, $width, $height ) = ( 4, 200, 400 );
53 <p>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;</p>
54 <pre> my $piddle = zeros( byte, $bytes_per_pixel, $width, $height );
57 <p>Create a normal $piddle with zeros, byte format and the Bpp x width x height dimensions.</p>
58 <pre> my $pointer = $piddle->get_dataref();
61 <p>Here is where we get the acutal data the piddle is pointing to. We will have SDL create a new surface from this function.</p>
62 <pre> my $surface = SDL::Surface->new_from( $pointer, $width, $height, 32,
63 $width * $bytes_per_pixel );
66 <p>Using the same dimensions we create the surface using new_form. The width * Bpp is the scanline (pitch) of the surface in bytes.</p>
67 <pre> warn "Made surface of $width, $height and ". $surface->format->BytesPerPixel;
68 return ( $piddle, $surface );
71 <p>Finally make sure that the surface acutally has the correct dimensions we gave.</p>
72 <p><strong>NOTE:</strong> $surface->format->BytesPerPixel must return 1,2,3,4. !!</p>
73 <p>Now you can blit and use the surface as needed; and do PDL operations as required.</p>
80 <h2 id="Operating_on_the_Surface_safely">Operating on the Surface safely</h2>
81 <div id="Operating_on_the_Surface_safely_CONT">
82 <p>To make sure SDL is in sync with the data. You must call SDL::Video::lock <strong>before</strong> doing PDL operations on the piddle.</p>
83 <pre> SDL::Video::lock_surface($surface);
85 $piddle ( :, 0 : rand(400), 0 : rand(200) ) .= pdl( rand(225), rand(225), rand(255), 255 );
88 <p>After that you can unlock the surface to blit.</p>
89 <pre> SDL::Video::unlock_surface($surface);
94 <h2 id="Error_due_to_BPP_at_blitting">Error due to BPP at blitting</h2>
95 <div id="Error_due_to_BPP_at_blitting_CONTENT">
96 <p>When blitting the new surface check for the return value to see if there has been a problem.</p>
97 <pre> my $b = SDL::Video::blit_surface(
98 $surface, SDL::Rect->new( 0, 0, $surface->w, $surface->h ),
99 $app, SDL::Rect->new( ( $app->w - $surface->w ) / 2, ( $app->h - $surface->h ) / 2, $app->w, $app->h )
102 die "Could not blit: " . SDL::get_error() if ( $b == -1 );
105 <p>If the error message is 'Blit combination not supported' that means that the BPP is incorrect or incosistent with the dimensions.
106 After that a simple update_rect will so your new surface on the screen.</p>