SDL图像添加模糊过滤器以C编码

Question

我有使用SDL libary的代码。代码加载图片。我们可以保存新图像并添加一些过滤器，这是我的问题。

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "SDL.h"
#include "SDL_image.h"

void Filter(unsigned char * buf, int width,int height,int size,char bpp) ;


SDL_Surface* Load_image(char *file_name)
{
        /* Open the image file */
        SDL_Surface* tmp = IMG_Load(file_name);
        if ( tmp == NULL ) {
            fprintf(stderr, "Couldn't load %s: %s\n",
                    file_name, SDL_GetError());
                exit(0);
        }
        return tmp; 
}

void Paint(SDL_Surface* image, SDL_Surface* screen)
{
        SDL_BlitSurface(image, NULL, screen, NULL);
        SDL_UpdateRect(screen, 0, 0, 0, 0);
};





int main(int argc, char *argv[])
{
    Uint32 flags;
    SDL_Surface *screen, *image;
    int depth, done;
    SDL_Event event;

    /* Check command line usage */
    if ( ! argv[1] ) {
        fprintf(stderr, "Usage: %s <image_file>, (int) size\n", argv[0]);
        return(1);
    }

    if ( ! argv[2] ) {
        fprintf(stderr, "Usage: %s <image_file>, (int) size\n", argv[0]);
        return(1);
    }

    /* Initialize the SDL library */
    if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
        fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
        return(255);
    }

    flags = SDL_SWSURFACE;
    image = Load_image( argv[1] );
    printf( "\n\nImage properts:\n" );
    printf( "BitsPerPixel = %i \n", image->format->BitsPerPixel );
    printf( "BytesPerPixel = %i \n", image->format->BytesPerPixel );
    printf( "width %d ,height %d \n\n", image->w, image->h );       

    SDL_WM_SetCaption(argv[1], "showimage");

    /* Create a display for the image */
    depth = SDL_VideoModeOK(image->w, image->h, 32, flags);
    /* Use the deepest native mode, except that we emulate 32bpp
       for viewing non-indexed images on 8bpp screens */
    if ( depth == 0 ) {
        if ( image->format->BytesPerPixel > 1 ) {
            depth = 32;
        } else {
            depth = 8;
        }
    } else
    if ( (image->format->BytesPerPixel > 1) && (depth == 8) ) {
            depth = 32;
    }
    if(depth == 8)
        flags |= SDL_HWPALETTE;
    screen = SDL_SetVideoMode(image->w, image->h, depth, flags);
    if ( screen == NULL ) {
        fprintf(stderr,"Couldn't set %dx%dx%d video mode: %s\n",
            image->w, image->h, depth, SDL_GetError());
    }

    /* Set the palette, if one exists */
    if ( image->format->palette ) {
        SDL_SetColors(screen, image->format->palette->colors,
                  0, image->format->palette->ncolors);
    }


    /* Display the image */
    Paint(image, screen);

    done = 0;
    int size =atoi( argv[2] );
    printf("Actual size is: %d\n", size);
    while ( ! done ) {
        if ( SDL_PollEvent(&event) ) {
            switch (event.type) {
                case SDL_KEYUP:
                switch (event.key.keysym.sym) {
                    case SDLK_ESCAPE:
                    case SDLK_TAB:
                    case SDLK_q:
                    done = 1;
                    break;
                    case SDLK_SPACE:
                    case SDLK_f:
                    SDL_LockSurface(image);

                    printf("Start filtering...  ");
                    Filter(image->pixels,image->w,image->h, size, image->format->BytesPerPixel );
                    printf("Done.\n");

                    SDL_UnlockSurface(image);

                    printf("Repainting after filtered...  ");
                    Paint(image, screen);
                    printf("Done.\n");

                    break;
                    case SDLK_r:
                    printf("Reloading image...  ");
                    image = Load_image( argv[1] );
                    Paint(image,screen);
                    printf("Done.\n");
                    break;
                    case SDLK_PAGEDOWN:
                    case SDLK_DOWN:
                    case SDLK_KP_MINUS:
                    size--;
                    if (size==0) size--;
                    printf("Actual size is: %d\n", size);
                        break;
                    case SDLK_PAGEUP:
                    case SDLK_UP:
                    case SDLK_KP_PLUS:
                    size++;
                    if (size==0) size++;
                    printf("Actual size is: %d\n", size);
                    break;      
                   case SDLK_s:
                    printf("Saving surface at nowy.bmp ...");
                    SDL_SaveBMP(image, "nowy.bmp" ); 
                    printf("Done.\n");
                    default:
                    break; 

          printf("Done.\n");



          break;

            case SDLK_r:

          printf("Reloading image...  ");

          image = Load_image( argv[1] );

          Paint(image,screen);

          printf("Done.\n");

          break;

            case SDLK_PAGEDOWN:

            case SDLK_DOWN:

            case SDLK_KP_MINUS:

          size--;

          if (size==0) size--;

          printf("Actual size is: %d\n", size);

                break;

            case SDLK_PAGEUP:

            case SDLK_UP:

            case SDLK_KP_PLUS:

          size++;

          if (size==0) size++;

          printf("Actual size is: %d\n", size);

          break;    

           case SDLK_s:

          printf("Saving surface at nowy.bmp ...");

          SDL_SaveBMP(image, "new.bmp" ); 

          printf("Done.\n");
                }
                break;
//              case  SDL_MOUSEBUTTONDOWN:
//              done = 1;
//              break;
                            case SDL_QUIT:
                done = 1;
                break;
                default:
                break;
            }
        } else {
            SDL_Delay(10);
        }
    }
    SDL_FreeSurface(image);
    /* We're done! */
    SDL_Quit();
    return(0);
}

我需要在void Filter中实现blur函数。我对此一无所知。我知道我们需要使用两个for循环。首先是高度，第二个是宽度。