hello4_animation.c

/**
 * hello4_animation.c - Animates hello.png scrolling up the window
 */

#include <stdio.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_timer.h>
#include <SDL2/SDL_image.h>

#define WINDOW_WIDTH (640)
#define WINDOW_HEIGHT (480)

// speed in pixels/second
#define SCROLL_SPEED (300)

int main(void)
{
    // attempt to initialize graphics and timer system
    if (SDL_Init(SDL_INIT_VIDEO|SDL_INIT_TIMER) != 0)
    {
        printf("error initializing SDL: %s\n", SDL_GetError());
        return 1;
    }

    SDL_Window* win = SDL_CreateWindow("Hello, CS50!",
                                       SDL_WINDOWPOS_CENTERED,
                                       SDL_WINDOWPOS_CENTERED,
                                       WINDOW_WIDTH, WINDOW_HEIGHT,0);
    if (!win)
    {
        printf("error creating window: %s\n", SDL_GetError());
        SDL_Quit();
	    return 1;
    }

    // create a renderer, which sets up the graphics hardware
    Uint32 render_flags = SDL_RENDERER_ACCELERATED;
    SDL_Renderer* rend = SDL_CreateRenderer(win, -1, render_flags);
    if (!rend)
    {
      printf("error creating renderer: %s\n", SDL_GetError());
      SDL_DestroyWindow(win);
      SDL_Quit();
      return 1;
    }

    // load the image into memory using SDL_image library function
    SDL_Surface* surface = IMG_Load("resources/hello.png");
    if (!surface)
    {
        printf("error creating surface\n");
        SDL_DestroyRenderer(rend);
        SDL_DestroyWindow(win);
        SDL_Quit();
        return 1;
    }

    // load the image data into the graphics hardware's memory
    SDL_Texture* tex = SDL_CreateTextureFromSurface(rend, surface);
    SDL_FreeSurface(surface);
    if (!tex)
    {
        printf("error creating texture: %s\n", SDL_GetError());
        SDL_DestroyRenderer(rend);
        SDL_DestroyWindow(win);
        SDL_Quit();
        return 1;
    }

    // struct to hold the position and size of the sprite
    SDL_Rect dest;

    // get the dimensions of texture
    SDL_QueryTexture(tex, NULL, NULL, &dest.w, &dest.h);

    // position the sprite at the bottom center of the window
    // origin is the top left corner, positive y is down
    dest.x = (WINDOW_WIDTH - dest.w) / 2;

    // require float resolution for y position
    float y_pos = WINDOW_HEIGHT;

    // animation loop
    while (dest.y >= -dest.h)
    {
        // clear the window
        SDL_RenderClear(rend);

        // set the y position in the struct
        dest.y = (int) y_pos;
    
        // draw the image to the window
        SDL_RenderCopy(rend, tex, NULL, &dest);
        SDL_RenderPresent(rend);

        // update sprite position
        y_pos -= (float) SCROLL_SPEED / 60;

        // wait 1/60th of a second
        SDL_Delay(1000/60);
    }
    
    // clean up resources before exiting
    SDL_DestroyTexture(tex);
    SDL_DestroyRenderer(rend);
    SDL_DestroyWindow(win);
    SDL_Quit();
}