X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pages%2Fblog-0013.html-inc;h=2e202e79e222745e30148733ba74569908ecbd32;hb=6855e5615bff699e656bdd67be71ac965fc77f54;hp=1cfd8aee1ddc458167812a4f7f93e0d308534f72;hpb=65a973147068b3edbbb232aa50fd53a79d7daaef;p=sdlgit%2FSDL-Site.git diff --git a/pages/blog-0013.html-inc b/pages/blog-0013.html-inc index 1cfd8ae..2e202e7 100644 --- a/pages/blog-0013.html-inc +++ b/pages/blog-0013.html-inc @@ -1,14 +1,81 @@

-SDL_perl 2.3_5 is out! +Providing direct memory access to SDL_Surface's pixels

-
We keep on rolling,
-rolling,
-waiting on the world to turn.
-

-So a new alpha is out on CPAN, after a bit of a break. We are trying to pick up our speed again. Hopefully we can get back to the weekly updates. This week I am going to try to get Mixer and TTF bindings test, redesigned and doc'd. Hopefully soon we can start working on Frozen Bubble, as things are starting to come together. This alpha release has finally given us a good implementation of SDL Timers. Also Daniel Ruoso has also started a series blog posts of making games with SDL Perl. Hopefully this can get more people in SDL, cause we can sure use the help!
+

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:



-More to come --yapgh
-


-

\ 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.

+


+

\ No newline at end of file