resize.h

//resize.c - has all you need to get high-quality interpolated image scaling - up & down!
//please see resize.c for more information about who has contributed to this library

#ifndef __RESIZE_FILTERS__
#define __RESIZE_FILTERS__

#include <SDL/SDL.h>

//Here are the only 2 functions you need:
//NULL will be returned if the passed in surface "image" is invalid
SDL_Surface* SDL_ResizeFactor(SDL_Surface *image, float scalefactor,    int filter);
SDL_Surface* SDL_ResizeXY    (SDL_Surface *image, int new_w, int new_h, int filter);

//Here are overloaded C++ versions, with filter default as high quality.
#ifdef __cplusplus
SDL_Surface* SDL_Resize(SDL_Surface *image, float scalefactor,    int filter = 7);
SDL_Surface* SDL_Resize(SDL_Surface *image, int new_w, int new_h, int filter = 7);
#endif

/*The passed-in surface is freed by SDL_Resize, so it works nicely to pass in surfaces
  as themselves:
  e.g. pic = SDL_ResizeFactor(pic, 0.75, 7); (or pic = SDL_Resize(pic, 0.75);)
  This will shrink pic to 75% of original size. No other cleanup necessary.
  Another good way to use it is on initialization:
  e.g. SDL_Surface *pic = SDL_ResizeXY(SDL_LoadBMP("mypic.bmp"),50,50,7);
  This will give you mypic.png at size 50x50(regardless of original dimensions)
  if mypic.bmp did not load correctly, pic will be NULL.
*/

/*
Filters are as follows:
1 = box filter - fastest/ugliest.
2 =        triangle filter - possible visual anomalies
3 = bell filter - possible visual anomalies
4 = B_spline filter - here is where it starts to get good.
5 =        hermite filter - relatively fast, good quality
6 =        Mitchell filter - also speedy, good quality
7 = Lanczos3 filter - slowest, but by far best quality. Very sharp!
If filter is not specified, Lanczos3 will be selected by default
*/

/*The code should compile as either C or C++, without any fuss, except maybe you specifying
  which kind to compile it as... -Dave Olsen
*/

#endif