I have been working on this game using SDL2.0 and C and hit a snag. As title say, I want to make image change when users press the keyboard, but it doesn't work.So I want to konw where the code is wrong.
Here is the code.
#include <stdio.h>
#include <sdl2/SDL.h>
#include <sdl2/SDL_image.h>
int main(int argc, char* args[]){
bool quit = false;
SDL_Event event;
SDL_Init(SDL_INIT_VIDEO);
SDL_Window * window = SDL_CreateWindow("SDL2 Displaying Image",
SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, 0);
SDL_Surface * image = SDL_LoadBMP("opening_ps1.bmp");
SDL_Texture * texture = SDL_CreateTextureFromSurface(renderer, image);
while (!quit){
SDL_WaitEvent(&event);
SDL_RenderCopy(renderer, texture, NULL, NULL);
SDL_RenderPresent(renderer);
while(SDL_PollEvent(&event)){
if(event.type == SDL_QUIT){
quit = true;
break;
}
if(event.type == SDL_KEYDOWN){
switch(event.key.keysym.sym){
case SDL_SCANCODE_A:
quit = false;
SDL_Renderer * renderer1 = SDL_CreateRenderer(window, -1, 0);
SDL_Surface * image1 = SDL_LoadBMP("opening_2.bmp");
SDL_Texture * texture1 = SDL_CreateTextureFromSurface(renderer1, image1);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer1, texture1, NULL, NULL);
SDL_RenderPresent(renderer1);
break;
}
}
}
}
SDL_FreeSurface(image);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
CodePudding user response：
Here is your code working perfectly, let me explain how it works! Please don't forget to change the file names, I have used pngs, but you can do the same thing with bmps.
SDL_image.h
First of all I have assumed that you might want to load other types of files than only bmps, and since you had that library in import I thought I can include that in the code!
The main loop
You had a double loop which is something you don't really need here, we can just have an infinite loop and the break condition inside.
The SDL_FreeSurface
Since after the textures have been created we no longer need surface, we can free them immediately
SDL_SCANCODE_A
This is what you were comparing the result of event.key.keysym.sym to, however the type of event.key.keysym.sym is SDL_Keycode so you had to compare it to SDLK_a in order to trigger the change of the image when the key a is pressed
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <stdbool.h>
int main(int argc, char *args[])
{
SDL_Event event;
SDL_Init(SDL_INIT_VIDEO);
IMG_Init(IMG_INIT_PNG);
SDL_Window *window = SDL_CreateWindow("SDL2 Displaying Image",
SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, 0);
SDL_Surface *image = IMG_Load("akward.png");
SDL_Texture *texture = SDL_CreateTextureFromSurface(renderer, image);
SDL_FreeSurface(image);
SDL_RenderCopy(renderer, texture, NULL, NULL);
SDL_RenderPresent(renderer);
while (1)
{
SDL_PollEvent(&event);
if (event.type == SDL_QUIT)
{
break;
}
if (event.type == SDL_KEYDOWN)
{
switch (event.key.keysym.sym)
{
case SDLK_a:
SDL_Surface *image1 = IMG_Load("output.png");
SDL_Texture *texture1 = SDL_CreateTextureFromSurface(renderer, image1);
SDL_FreeSurface(image1);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture1, NULL, NULL);
SDL_RenderPresent(renderer);
break;
}
}
}
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
EDIT:
Here is the code that will allow you to take all images from a directory and show them! I will do a brief explanation if you are interested. First of all I have written a macro that will allow you to specify the number of images in a directory, please make sure it is the correct number! I have put 5 for testing purposes!
#define IMG_NUMBER 5
I have created two more functions, the my_str_concat is just to concatenate the directory name and the file name so it can be opened by IMG_Load. The create_texture_array creates an array of textures so that they can be used by the main function afterwards
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <stdbool.h>
#include <dirent.h>
#include <errno.h>
#define IMG_NUMBER 5
char * my_str_concat(const char * input_directory, char * file_name)
{
size_t input_directory_size = strlen(input_directory);
//The 257 is for the max size of file_name
char * res = malloc(sizeof(char)*(input_directory_size 257));
strcpy(res,input_directory);
strcat(res,file_name);
return res;
}
SDL_Texture ** create_texture_array(const char * input_directory,SDL_Renderer *renderer)
{
SDL_Texture ** texture_array = malloc(sizeof(SDL_Texture *) * IMG_NUMBER);
int i = 0;
DIR *images_dir;
if (NULL == (images_dir = opendir(input_directory)))
{
fprintf(stderr, "Error : Failed to open input directory - %s\n", strerror(errno));
return NULL;
}
struct dirent * image_file;
while((image_file = readdir(images_dir)))
{
//We don't want to read current and parent directories!
if (!strcmp (image_file->d_name, "."))
{
continue;
}
if (!strcmp (image_file->d_name, ".."))
{
continue;
}
char * relative_file_path = my_str_concat(input_directory,image_file->d_name);
printf("%s\n",relative_file_path);
SDL_Surface *image = IMG_Load(relative_file_path);
free(relative_file_path);
SDL_Texture *texture = SDL_CreateTextureFromSurface(renderer, image);
SDL_FreeSurface(image);
texture_array[i] = texture;
i ;
}
return texture_array;
}
void free_array(SDL_Texture ** arr, size_t size)
{
for (size_t i = 0; i < size; i )
{
SDL_DestroyTexture(arr[i]);
}
}
int main(int argc, char *args[])
{
SDL_Event event;
int i = 0;
SDL_Init(SDL_INIT_VIDEO);
IMG_Init(IMG_INIT_PNG);
SDL_Window *window = SDL_CreateWindow("SDL2 Displaying Image",SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, 0);
SDL_Texture ** texture_array = create_texture_array("img/",renderer);
SDL_RenderCopy(renderer, texture_array[0], NULL, NULL);
SDL_RenderPresent(renderer);
while (1)
{
SDL_PollEvent(&event);
if (event.type == SDL_QUIT)
{
break;
}
if (event.type == SDL_KEYDOWN && i 1 < IMG_NUMBER)
{
switch (event.key.keysym.sym)
{
case SDLK_a:
i ;
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture_array[i], NULL, NULL);
SDL_RenderPresent(renderer);
break;
}
}
}
free_array(texture_array,IMG_NUMBER);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
I hope this will be helpful! If this does answer your question please don't hesitate to mark this answer as correct! Best regards,