gistfile1.c

#include "thumb.h"

gdImagePtr loadImage(char *path) {
    FILE *fp;
    gdImagePtr im; 

    fp = fopen(path, "rb");
    if (!fp) {
        assert_perror(errno);
    }   

    im = gdImageCreateFromJpeg(fp);
    fclose(fp);
    return im; 
}

void savePngImage(gdImagePtr im, char *path) {
    FILE *fp;
    fp = fopen(path, "wb");
    if (!fp)  {
        assert_perror(errno);
    }   
    gdImagePng(im, fp);
    fclose(fp);
    gdFree(im);
}

void thumbnail(char *path, char *tpath) {
        gdImagePtr src = loadImage(path);
        int w, h, tw = 100, th = 100;
        w = gdImageSX(src);
        h = gdImageSY(src);
        if ( w > h ) { 
            th = 100 * h / w;
            fflush(stdout);
        }   
        else {
            tw = 100 * w / h;
        }   
        gdImagePtr dst =  gdImageCreateTrueColor(tw, th);
        gdImageCopyResampled(dst, src, 0, 0, 0, 0, tw, th, w, h); 
        savePngImage(dst, tpath);
        gdFree(src);
}