SDL:Tutorials:2D Graphics
-- Work In Progress --
- include <cstdlib> // For some useful functions such as atexit :)
- include "SDL.h" // main SDL header
- define SCREEN_WIDTH 640
- define SCREEN_HEIGHT 480
- define true 1
- define false 0 //You might have to declare True and False.
- define COLORKEY 255, 0, 255 //Your Transparent colour
SDL_Surface *screen; //This pointer will reference the backbuffer
int InitVideo(Uint32 flags = SDL_DOUBLEBUF | SDL_FULLSCREEN) {
// Load SDL
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
fprintf(stderr, "Unable to initialize SDL: %s\n", SDL_GetError());
return false;
}
atexit(SDL_Quit); // Clean it up nicely :)
// fullscreen can be toggled at run time :) any you might want to change the flags with params?
//set the main screen to SCREEN_WIDTHxSCREEN_HEIGHT with a colour depth of 16:
screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 16, flags);
if (!screen) {
fprintf(stderr, "Unable to set video mode: %s\n", SDL_GetError());
return false;
}
return true;
}
Loading an Image: (Bitmap)
SDL_Surface* LoadImage(char *file, int &exitstate) {
SDL_Surface *tmp; tmp = SDL_LoadBMP(file);
if (!tmp) {
fprintf(stderr, "Error: '%s' could not be opened: %s\n", file, SDL_GetError());
exitstate = false;
return NULL;
} else {
if(SDL_SetColorKey(tmp, SDL_SRCCOLORKEY | SDL_RLEACCEL, SDL_MapRGB(tmp->format, COLORKEY)) == -1)
fprintf(stderr, "Warning: colorkey will not be used, reason: %s\n", SDL_GetError());
}
exitstate = true;
return tmp;
}
Loading an Image: (bmp,pnm,xpm,xcf,pcx,gif,jpg,tif,png,tga,lbm) in order to use these images in your program you must include the SDL_image library.
NB: This library converts the images into a SDL_Surface layer, where as the bitmap one above just copies the data across to a SDL_Surface. It is also NOT advised putting a LoadImage into a eventloop, and to precache your images you're going to use.
- include "SDL_image.h"
SDL_Surface* LoadImage(char *file, int &exitstate) {
SDL_Surface *tmp; tmp = IMG_Load(file);
if (!tmp) {
fprintf(stderr, "Error: '%s' could not be opened: %s\n", file, IMG_GetError());
exitstate = false;
return NULL;
} else {
if(SDL_SetColorKey(tmp, SDL_SRCCOLORKEY | SDL_RLEACCEL, SDL_MapRGB(tmp->format, COLORKEY)) == -1)
fprintf(stderr, "Warning: colorkey will not be used, reason: %s\n", SDL_GetError());
}
exitstate = true;
return tmp;
}
Drawing An Image:
void DrawImage(SDL_Surface *srcimg, int sx, int sy, int sw, int sh, SDL_Surface *dstimg, int dx, int dy, int alpha = 255) {
if ((!srcimg) || (alpha == 0)) return; //If theres no image, or its 100% transparent. SDL_Rect src, dst; src.x = sx; src.y = sy; src.w = sw; src.h = sh; dst.x = dx; dst.y = dy; dst.w = src.w; dst.h = src.h; //if (alpha != 255) SDL_SetAlpha(srcimg, SDL_SRCALPHA, alpha); // - This is incorrect, if alpha is 10, then set to 255, the image alpha will still be 10. SDL_SetAlpha(srcimg, SDL_SRCALPHA, alpha); SDL_BlitSurface(srcimg, &src, dstimg, &dst);
}
Clean Up Your Image:
...
SDL_FreeSurface(img_name);
...
It's that simple! Want it easier? Well, you can just copy everything below into a file:
// SDL_Functions: Copied from gpwiki.org.
- include <cstdlib> // For some useful functions such as atexit :)
- include "SDL.h" // main SDL header
- include "SDL_image.h" // image library, if your only using BMP's, get ride of this.
- define SCREEN_WIDTH 640
- define SCREEN_HEIGHT 480
- define true 1
- define false 0 //You might have to declaire True and False.
- define COLORKEY 255, 0, 255 //Your Transparent colour
SDL_Surface *screen; //This pointer will reference the backbuffer
//I have set the flag SDL_SWSURFACE for a window :) int InitVideo(Uint32 flags = SDL_DOUBLEBUF | SDL_SWSURFACE) {
// Load SDL
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
fprintf(stderr, "Unable to initialize SDL: %s\n", SDL_GetError());
return false;
}
atexit(SDL_Quit); // Clean it up nicely :)
// fullscreen can be toggled at run time :) any you might want to change the flags with params?
//set the main screen to SCREEN_WIDTHxSCREEN_HEIGHT with a colour depth of 16:
screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 16, flags);
if (screen == NULL) {
fprintf(stderr, "Unable to set video mode: %s\n", SDL_GetError());
return false;
}
return true;
}
//--------------------------- Drawing Stuff ------------------------- SDL_Surface* LoadImage(char *file, int &exitstate) {
SDL_Surface *tmp;
tmp = IMG_Load(file);
exitstate = false;
if (tmp == NULL) {
fprintf(stderr, "Error: '%s' could not be opened: %s\n", file, IMG_GetError());
} else {
if(SDL_SetColorKey(tmp, SDL_SRCCOLORKEY | SDL_RLEACCEL, SDL_MapRGB(tmp->format, COLORKEY)) == -1)
fprintf(stderr, "Warning: colorkey will not be used, reason: %s\n", SDL_GetError());
exitstate = true;
}
return tmp;
}
void DrawImage(SDL_Surface *srcimg, int sx, int sy, int sw, int sh, SDL_Surface *dstimg, int dx, int dy, int alpha = 255) {
if ((srcimg == NULL) || (alpha == 0)) return; //If theres no image, or its 100% transparent. SDL_Rect src, dst; src.x = sx; src.y = sy; src.w = sw; src.h = sh; dst.x = dx; dst.y = dy; dst.w = src.w; dst.h = src.h; if (alpha != 255) SDL_SetAlpha(srcimg, SDL_SRCALPHA, alpha); SDL_BlitSurface(srcimg, &src, dstimg, &dst);
} //------------------------ The Game -----------------------
int main(int argc, char *argv[]) {
int res = 0; //Results
if (InitVideo() == false) return 1;
SDL_Surface *tux = LoadImage("tux.bmp",res);
if (res == false) return 1;
DrawImage(tux, 0,0, tux->w, tux->h, screen, 10, 10, 128);
SDL_Flip(screen); //Refresh the screen
SDL_Delay(2500); //Wait a bit :)
//cleanup SDL_FreeSurface(tux); return 0;
} //Remember the blank line at the end! gcc always bugs me about it :)
