X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pages%2Fblog-0015.html-inc;h=2e202e79e222745e30148733ba74569908ecbd32;hb=e785862422f3e827a242fc244bd57b23443887ce;hp=8978342f5d6ba01117e1a0dda5f9dbe8d8a5a674;hpb=a05e5d4499fb58198e463162d0385e8a156e1f03;p=sdlgit%2FSDL-Site.git diff --git a/pages/blog-0015.html-inc b/pages/blog-0015.html-inc index 8978342..2e202e7 100644 --- a/pages/blog-0015.html-inc +++ b/pages/blog-0015.html-inc @@ -1,36 +1,81 @@

-SDL Perl Showcase +Providing direct memory access to SDL_Surface's pixels

-
-SDL_Mixer and Effects
+

In an attempt to make pixel access easier on SDL_Surface pixels. I have started work on SDLx::Surface. So far I have only start on the 32 bpp surfaces.


+

The general idea is to make Pointer Values (PV) of each pixel in the surface and place them into a 2D matrix. First I make pointer values like this:


+
SV * get_pixel32 (SDL_Surface *surface, int x, int y)
+{
+ //Convert the pixels to 32 bit 
+ Uint32 *pixels = (Uint32 *)surface->pixels; 
+
+ //Get the requested pixel  
+ Uint32* u_ptr =  pixels + ( y * surface->w ) + x ; 
+
+        SV* sv = newSVpv("a",1); //Make a temp SV* value on the go
+        SvCUR_set(sv, sizeof(Uint32)); //Specify the new CUR length
+ SvLEN_set(sv, sizeof(Uint32)); //Specify the LEN length
+        SvPV_set(sv,(char*)u_ptr); // set the actual pixel's pointer as the memory space to use
+
+ return sv; //make a modifiable reference using u_ptr's place as the memory :)
+
+}
+

+

Next I loop through all the pixels and put them in a 2D array format, shown below: 

AV * construct_p_matrix ( SDL_Surface *surface )
+{
+    AV * matrix = newAV();
+     int i, j;
+     for(  i =0 ; i < surface->w; i++)
+      {
+        AV * matrix_row = newAV();
+        for( j =0 ; j < surface->h; j++)
+        {
+           av_push(matrix_row, get_pixel32(surface, i,j) );
+        }
+        av_push(matrix, newRV_noinc((SV*) matrix_row) );
+      }
+
+ return matrix;
+}
+

+

You can see the complete here.


+

In Perl I can do a get access on this pixel using:



-

-This demo shows the new work we have finished for SDL_Mixer support in SDL_perl . (FROGGS++)
-
-
-
-
-Get it at: playlist.pl, you need some .ogg files to play in the same directory. Use the down key to go through them.
-
-
-SDL_TTF support
-
-
-

-
-This shows the current work on SDL_TTF support. UTF8 and Uncicode are supported.
-
-See the t/ttf.t test in github SDL_perl.
-
-
-
-Spinner (Destiny Swirl) Arcade Game
-

-
And finally as a proof of concept we have been working a simple arcade game to test our bugs, and scope out our high level bindings. You can get it at the Spinner repo. This wiki page will help you set up for your platforms. 
-


-

\ No newline at end of file +
my $surf32_matrix = SDLx::Surface::pixel_array($screen_surface);
+   print unpack 'b*', $surf32_matrix->[0][0]; # pixel value at x = 0 and y =0
+#OUTPUT:
+# 11111111000000000000000000000000
+

+

The structure of the PV is using Devel::Peek is :


+
print Dump $surf32_matrix->[0][0];
+#OUTPUT:
+#SV = PV(0xed0dbc) at 0xeb5344
+#  REFCNT = 1
+#  FLAGS = (POK,pPOK)
+#  PV = 0x9e04ac "\0\0\377\0"
+#  CUR = 4
+#  LEN = 4
+

+

The problem is in setting the value of this pointer value. I have tried the following things with no success:


+
if ( SDL::Video::MUSTLOCK($screen_surface) ) {
+    return if ( SDL::Video::lock_surface($screen_surface) < 0 ); #required for pixel operations
+}
+
+#USING pack
+
+my $green = pack 'b*', '11111111000000000000000000000000';
+substr( $surf32_matrix->[0][0], 0, 8 * 4, $green); #no change
+#substr( $surf32_matrix->[0][0], 0, 8 * 4, 0xFF000000); segfault
+substr( ${$surf32_matrix->[0][0]}, 0, 8 * 4, 0xFF000000); #no change
+#$surf32_matrix->[0][0] = $green; SEGFAULT's cannot write to memory
+${$surf32_matrix->[0][0]} = $green; #no change
+
+
+SDL::Video::unlock_surface($screen_surface)
+  if ( SDL::Video::MUSTLOCK($screen_surface) );
+

+

You can see an example here.


+

Any help will be greatly appreciated.

+


+

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