libsegl/sdlfuncs.cpp

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2008-02-09 13:43:23 +01:00
#include "sdlfuncs.h"
Uint32 getPixel(SDL_Surface *surface, int x, int y)
{
int bpp = surface->format->BytesPerPixel;
/* Here p is the address to the pixel we want to retrieve */
Uint8 *p = (Uint8 *)surface->pixels + y * surface->pitch + x * bpp;
switch(bpp) {
case 1:
return *p;
case 2:
return *(Uint16 *)p;
case 3:
if(SDL_BYTEORDER == SDL_BIG_ENDIAN)
return p[0] << 16 | p[1] << 8 | p[2];
else
return p[0] | p[1] << 8 | p[2] << 16;
case 4:
return *(Uint32 *)p;
default:
return 0; /* shouldn't happen, but avoids warnings */
}
}
void setPixel(SDL_Surface *surface, int x, int y, Uint32 pixel)
{
int bpp = surface->format->BytesPerPixel;
/* Here p is the address to the pixel we want to set */
Uint8 *p = (Uint8 *)surface->pixels + y * surface->pitch + x * bpp;
switch(bpp) {
case 1:
*p = pixel;
break;
case 2:
*(Uint16 *)p = pixel;
break;
case 3:
if(SDL_BYTEORDER == SDL_BIG_ENDIAN) {
p[0] = (pixel >> 16) & 0xff;
p[1] = (pixel >> 8) & 0xff;
p[2] = pixel & 0xff;
} else {
p[0] = pixel & 0xff;
p[1] = (pixel >> 8) & 0xff;
p[2] = (pixel >> 16) & 0xff;
}
break;
case 4:
*(Uint32 *)p = pixel;
break;
}
}
void swapPixel(SDL_Surface *surface, int x1, int y1, int x2, int y2) {
Uint32 a,b;
a = getPixel(surface, x1, y1);
b = getPixel(surface, x2, y2);
setPixel(surface, x1, y1, b);
setPixel(surface, x2, y2, a);
}
void mirrorSurfaceMiddleX(SDL_Surface *surface) {
SDL_LockSurface(surface);
int upto = surface->h / 2;
for(int i=0; i<upto; i++) {
for(int x=0; x<surface->w; x++) {
swapPixel(surface, x, i, x, surface->h-1-i);
}
}
SDL_UnlockSurface(surface);
}