我正在搞乱SDL,我决定制作一个程序,打开图像作为主屏幕的背景,并使其动态化,因此不同大小的图像将导致不同大小的屏幕。问题是,我无法弄清楚为什么它不让我。我可以编译,但是当我尝试创建屏幕时程序会出错,因为背景图像由于某种未知原因而被取消。知道为什么吗?
该计划非常小:
#include <iostream>
#include "SDL/SDL.h"
#define bpp 32
int init(){
if (SDL_Init(SDL_INIT_EVERYTHING) == -1)
return 1;
// will init ttf later
return 0;
}
SDL_Surface * open_image(std::string image_name){
SDL_Surface * loaded_image = SDL_LoadBMP(image_name.c_str());
if (loaded_image){
SDL_Surface * optimized_image = SDL_DisplayFormat(loaded_image); // becomes NULL
SDL_FreeSurface(loaded_image);
return optimized_image;
}
return loaded_image;
}
int main(int argc, char * argv[]){
if (init())
return 1;
SDL_Surface * background = open_image("hello.bmp");
SDL_Surface * screen = SDL_SetVideoMode(background -> w, background -> h, bpp, SDL_SWSURFACE); // erroring here
SDL_BlitSurface(background, NULL, screen, NULL);
if (SDL_Flip(screen) == -1)
return 1;
bool quit = false;
SDL_Event event;
while (!quit)
while (SDL_PollEvent(&event))
if (event.type == SDL_QUIT)
quit = true;
return 0;
}
我收到错误3,显然是访问不存在的值。在这种情况下,它是w和h来自背景,因为background是NULL,即使它不应该是
答案 0 :(得分:2)
您无法在不调用SDL_SetVideoMode之前调用SDL_DisplayFormat。
我修复了你的代码:
SDL_Surface * screen = SDL_SetVideoMode(512, 512, bpp, SDL_SWSURFACE);
SDL_Surface * background = open_image("hello.bmp");
screen = SDL_SetVideoMode(background -> w, background -> h, bpp, SDL_SWSURFACE);