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:
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.