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Re: SDL Surfaces and Rectangles

by PodMaster (Abbot)
on Jan 31, 2006 at 11:08 UTC ( #526709=note: print w/replies, xml ) Need Help??


in reply to SDL Surfaces and Rectangles

I'd expect from the documentation that it would work the same way, but apparently it doesn't. It appears to be blitting on itself.
Works fine for me :/ as I expect it should (SDL_Rect -- Defines a rectangular area)
Perl v5.8.4 WinXP
SDL 2.1.0 built against libsdl 1.2.7.0

update: to clarify, in my tests both behave the same.
SDL_BlitSurface

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
** The third rule of perl club is a statement of fact: pod is sexy.

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Re^2: SDL Surfaces and Rectangles
by shotgunefx (Parson) on Jan 31, 2006 at 11:44 UTC
    There is something I'm missing here. I did another example and it does indeed work. Here's a cut down version that illustrates the problem.

    There is an image here to test with. Note that this GIF image was saved with cropping. So the frame will jitter. My orginal code dealt with this but to keep it to the point, I've hacked it out.

    The load_sprites function if not passed a -tmpfile parameter, will try and create a temporary image at
    "/tmp/sprite-im.gif"

    What happens for me is that with the src and dst rectangles the same, it will run through the animation once and only once. You'll just keep seeing the what appears to be the last frame. If you change the blit to use the seperate but identical dimensionally $sprite->{-dst_rect}, it works as expected.

    I'm really at a loss here.
    #!/usr/bin/perl use strict; use warnings; use Image::Magick; use SDL; use SDL::App; use SDL::Surface; use SDL::Color; use SDL::Rect; use Data::Dumper; my $app = SDL::App->new( -title=>"Sprite Test", -width =>100, -height => 100, -depth => 24, ); my $sprite = load_sprites(-file=>"testlight-a.gif"); my $app_rect = SDL::Rect->new( -height => 480, -width => 600, -x => 0, + -y => 0 ) or die "Couldn't create SDL::Rect !"; for (0..100){ for my $im ( @{ $sprite->{-frames} } ){ $im->blit( $sprite->{-src_rect} ,$app, $sprite->{-src_rect}); #s +rc = src = not work. #$im->blit( $sprite->{-src_rect} ,$app, $sprite->{-dst_rect}); # +src = dst = works $app->update($sprite->{-src_rect}); $app->delay(200); } } #------------------------------------------------------------- # # Oddities: # If Surface not initialized via graphic file, blits will not take. # Image::Magick->Write is succeeding but not returning count of images + written. sub load_sprites { my %args = ( -file => undef, -tmpfile => '/tmp/sprite-im.gif', @_, ); die "File [$args{-file}] doesn't exist!" unless -e $args{-file}; my ($src_rect,$dst_rect, $magick, @frames, $x ); $magick = Image::Magick->new() or die "Couldn't create Image::Ma +gick object!: $!"; $magick->Read($args{-file}) ; my ($iw,$ih) = $magick->Get( qw /width height/) ; # Get the height + and width of image $src_rect = SDL::Rect->new( -height => $ih, -width => $iw, -x => 0 +, -y => 0 ) or die "Couldn't create SDL::Rect !"; $dst_rect = SDL::Rect->new( -height => $ih, -width => $iw, -x => 0 +, -y => 0 ) or die "Couldn't create SDL::Rect !"; foreach my $im (@$magick) { my ($w,$h,$ws,$hs); # Width, height, start of bounding box, # don't know if this returns valid info fo +r all formats. if ($im->Get( qw /width height bounding-box/ )=~m/^(\d+)x(\d+) +\+(\d+)\+(\d)/){ ($w,$h,$ws,$hs) = ($1,$2,$3,$4); warn join(", ",($w,$h,$ws,$hs)); }else{ die "Error retrieving image properties!"; } # For newer perls, could probably skip the tmp file altogther +and read/write a scalar $im->Write( filename => $args{-tmpfile}); # Isn't returning the count. According to the docs, should be +number of images written so can't error check. push @frames, SDL::Surface->new( -name => $args{-tmpfile}) ; } return { -frames=>\@frames, -x=>0, -y=>0, -src_rect=>$src_rect,-ds +t_rect=>$dst_rect}; }


    -Lee

    perl digital dash (in progress)
Re^2: SDL Surfaces and Rectangles
by shotgunefx (Parson) on Jan 31, 2006 at 11:48 UTC
    Looking at your link again, it does explain it.

    The final blit rectangle is saved in dstrect after all clipping is performed (srcrect is not modified)

    That's a huge gotcha that I've not come across in any of the SDL Perl documents I've found.

    Thanks++


    -Lee

    perl digital dash (in progress)
      No prob. This is what bothers me with SDL and Tk. They bother to include documentation, but its horribly incomplete. Whereas wxPerl forces you to always refer to the external wxWidgets documentation (granted its annotated).

      Hope you send in a bug report :)

      MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
      I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
      ** The third rule of perl club is a statement of fact: pod is sexy.

        Yes, horrible. I'd like to start working on that myself. That's why I'm trying to get the latest version working. I don't want to be submitting bugs for things that have been fixed.

        I'm going to take a guess that when the src = dst, it doesn't think it needs to copy. The few tests I've tried seem to confirm it.

        -Lee

        perl digital dash (in progress)

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