sdlgpu-filtering.cc

// g++ -Wall -O -o sdlgpu-test $(pkg-config SDL2_gpu --cflags) $(sdl2-config --cflags) sdlgpu-test.cc $(pkg-config SDL2_gpu --libs) $(sdl2-config --libs)

#include <SDL_gpu.h>

int main(int argc, char* argv[])
{
    GPU_SetDebugLevel(GPU_DEBUG_LEVEL_MAX);
    
    GPU_Target* screen = GPU_Init(400, 300, GPU_DEFAULT_INIT_FLAGS);
    if (!screen)
        return 1;

    SDL_Surface *surf = SDL_CreateRGBSurface(0, 16, 16, 32,
                                             0xFF000000,
                                             0x00FF0000,
                                             0x0000FF00,
                                             0x000000FF);
    SDL_Rect rect;

    rect.x = 0;
    rect.y = 0;
    rect.w = 16;
    rect.h = 16;
    SDL_FillRect(surf, &rect, SDL_MapRGBA(surf->format, 64, 64, 64, 255));
    
    rect.w = 4;
    rect.h = 4;

    rect.x = 4; rect.y = 4; SDL_FillRect(surf, &rect, SDL_MapRGBA(surf->format, 255, 0, 0, 255));
    rect.x = 4; rect.y = 8; SDL_FillRect(surf, &rect, SDL_MapRGBA(surf->format, 0, 255, 0, 255));
    rect.x = 8; rect.y = 4; SDL_FillRect(surf, &rect, SDL_MapRGBA(surf->format, 0, 0, 255, 255));
    rect.x = 8; rect.y = 8; SDL_FillRect(surf, &rect, SDL_MapRGBA(surf->format, 255, 255, 0, 255));

    GPU_Image *tex = GPU_CopyImageFromSurface(surf);
    SDL_FreeSurface(surf);

    GPU_SetAnchor(tex, 0, 0);
    GPU_SetBlending(tex, GPU_FALSE);
    
    bool done = false;
    while (!done) {
        SDL_Event event;

        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT)
                done = true;
            else if (event.type == SDL_KEYDOWN) {
                if(event.key.keysym.sym == SDLK_ESCAPE)
                    done = true;
            }
        
            GPU_ClearRGBA(screen, 128, 128, 128, 255);

            GPU_Rect src, dest;

            // whole texture
            src.x = 0;
            src.y = 0;
            src.w = tex->w;
            src.h = tex->h;
            dest.x = 10;
            dest.y = 10;
            dest.w = 256;
            dest.h = 256;
            GPU_SetImageFilter(tex, GPU_FILTER_NEAREST);
            GPU_BlitRect(tex, &src, screen, &dest);

            // red subtexture only:

            // NEAREST
            src.x = 4;
            src.y = 4;
            src.w = 4;
            src.h = 4;
            dest.x = 300;
            dest.y = 10;
            dest.w = 64;
            dest.h = 64;
            GPU_SetImageFilter(tex, GPU_FILTER_NEAREST);
            GPU_BlitRect(tex, &src, screen, &dest);

            // LINEAR
            src.x = 4;
            src.y = 4;
            src.w = 4;
            src.h = 4;
            dest.x = 300;
            dest.y = 84;
            dest.w = 64;
            dest.h = 64;
            GPU_SetImageFilter(tex, GPU_FILTER_LINEAR);
            GPU_BlitRect(tex, &src, screen, &dest);

            // disable snap, fix up coordinates by hand
            src.x = 4.5;
            src.y = 4.5;
            src.w = 3;
            src.h = 3;
            dest.x = 300;
            dest.y = 158;
            dest.w = 64;
            dest.h = 64;
            GPU_SetSnapMode(tex, GPU_SNAP_NONE);
            GPU_SetImageFilter(tex, GPU_FILTER_LINEAR);
            GPU_BlitRect(tex, &src, screen, &dest);

            GPU_Flip(screen);
        }
    }

    GPU_Quit();
    return 0;
}