nese/v1/src/sdl_effect.c

#include "sdl_effect.h"

/*
static const uint8_t the_effect[3][3][4] = {
    {{14, 0, 216, 204}, {16, 0, 0, 217}, {21, 225, 1, 0},},
    {{81, 0,   1,   1}, {83, 1, 0,   3}, {72,   2, 0, 0},},
    {{ 5, 0, 252, 245}, { 6, 0, 0, 243}, {10, 236, 1, 0},},
};

static const int effect_w = 3;
static const int effect_h = 3;
*/

static const uint8_t the_effect[2][2][4] = {
    {{ 25, 0, 0, 0}, {  1, 0, 0, 0},},
    {{144, 0, 0, 0}, {133, 0, 0, 0},},
};

static const int effect_w = 2;
static const int effect_h = 2;


sdl_effect* effect_init(SDL_Renderer* renderer,
                        int view_w, int view_h) {
    const int tex_w = view_w * 2;
    const int tex_h = view_h * 2;

    SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "1");

    SDL_Texture* effect = SDL_CreateTexture(
            renderer, SDL_PIXELFORMAT_BGRA8888,
            SDL_TEXTUREACCESS_STREAMING, tex_w, tex_h
        );

    void* pixels = NULL;
    int pitch = 0;
    SDL_LockTexture(effect, NULL, &pixels, &pitch);

    uint8_t* dst_line = (uint8_t*)pixels;
    for (int y = 0; y < tex_h; ++y) {
        uint8_t* dst = dst_line;
        for (int x = 0; x < tex_w; ++x) {
            dst[0] = the_effect[y % effect_h][x % effect_w][0];
            dst[1] = the_effect[y % effect_h][x % effect_w][1];
            dst[2] = the_effect[y % effect_h][x % effect_w][2];
            dst[3] = the_effect[y % effect_h][x % effect_w][3];
            dst += 4;
        }
        dst_line += pitch;
    }

    SDL_UnlockTexture(effect);

    SDL_SetTextureBlendMode(effect, SDL_BLENDMODE_BLEND);

    return (sdl_effect*)effect;
}

void effect_done(sdl_effect* effect) {
    if (effect) {
        SDL_DestroyTexture((SDL_Texture*)effect);
    }
}

void effect_apply(sdl_effect* effect, SDL_Renderer* renderer,
                  const SDL_Rect* rect) {
    if (effect) {
        SDL_RenderCopy(renderer, (SDL_Texture*)effect,
                       NULL, rect);
    }
}