analysis

C/ssvep_4.c

+#include <stdio.h>
+#include <stdbool.h>
+#include <SDL2/SDL.h>
+
+const int WINDOW_WIDTH = 1920;
+const int WINDOW_HEIGHT = 1080;
+
+int main(int argc, char *argv[]) {
+    
+    if (argc != 5) {
+        printf("Usage: %s <freq1> <freq2> <freq3> <freq4>\n", argv[0]);
+        return 1;
+    }
+
+    int frequencies[4];
+
+    for (int i = 0; i < 4; i++) {
+        frequencies[i] = atoi(argv[i + 1]);
+        if (frequencies[i] <= 0) {
+            printf("Invalid frequency. Please provide positive integer values.\n");
+            return 1;
+        }
+    }
+
+    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+        printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
+        return 1;
+    }
+
+    SDL_Window *window = SDL_CreateWindow("Multi Flicker",
+                                          SDL_WINDOWPOS_CENTERED,
+                                          SDL_WINDOWPOS_CENTERED,
+                                          WINDOW_WIDTH, WINDOW_HEIGHT,
+                                          SDL_WINDOW_SHOWN);
+    if (window == NULL) {
+        printf("Window could not be created! SDL_Error: %s\n", SDL_GetError());
+        SDL_Quit();
+        return 1;
+    }
+
+    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
+    if (renderer == NULL) {
+        printf("Renderer could not be created! SDL_Error: %s\n", SDL_GetError());
+        SDL_DestroyWindow(window);
+        SDL_Quit();
+        return 1;
+    }
+
+
+    Uint32 intervals[4];
+    Uint32 next_flicker[4];
+    bool white[4] = {false, false, false, false};
+
+    for (int i = 0; i < 4; i++) {
+        intervals[i] = (Uint32)(1000.0 / (2* frequencies[i]));
+        next_flicker[i] = SDL_GetTicks() + intervals[i];
+    }
+
+    bool quit = false;
+    SDL_Event event;
+
+    while (!quit) {
+        while (SDL_PollEvent(&event)) {
+            if (event.type == SDL_QUIT || (event.type == SDL_KEYDOWN && event.key.keysym.sym == SDLK_ESCAPE)) {
+                quit = true;
+            }
+        }
+
+        for (int i = 0; i < 4; i++) {
+            if (SDL_GetTicks() >= next_flicker[i]) {
+                white[i] = !white[i];
+                next_flicker[i] += intervals[i];
+            }
+        }
+
+        SDL_SetRenderDrawColor(renderer, 128, 128, 128, 255);
+        SDL_RenderClear(renderer);
+
+        for (int i = 0; i < 4; i++) {
+            SDL_Rect segment;
+            segment.w = WINDOW_WIDTH / 2;
+            segment.h = WINDOW_HEIGHT / 2;
+            segment.x = (i % 2) * segment.w;
+            segment.y = (i / 2) * segment.h;
+
+            SDL_SetRenderDrawColor(renderer, white[i] ? 255 : 0, white[i] ? 255 : 0, white[i] ? 255 : 0, 255);
+            SDL_RenderFillRect(renderer, &segment);
+        }
+
+        SDL_RenderPresent(renderer);
+    }
+
+    SDL_DestroyRenderer(renderer);
+    SDL_DestroyWindow(window);
+    SDL_Quit();
+    return 0;
+}
+