/*
 * Generate gif file to visualize the microstructure
 */

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

/* gd library */
#include <gd.h>
#include <gdfontl.h>

void generate_snapshot(const char *filename, const char *label, int nx, int ny, double *c)
{

    FILE *fp;
    int i, j;
    int inten;
    gdImagePtr im;   /* Declare the image */
    int gray[256];   /* array of gray shades */
    int red;

    /* Allocate the image: nx pixels across by ny pixels tall */
    im = gdImageCreate(nx, ny);

    /* Allocate the color red. */
    red = gdImageColorAllocate(im, 255, 0, 0);  

    /* Allocate gray colors */
    for (i = 0; i < 256; i++) {
        gray[i] = gdImageColorAllocate(im, i, i, i);  
    }

    for (i = 0; i < nx; ++i) {
        for (j = 0; j < ny; ++j) {
            inten = (int) (255.0 * c[j + ny * i]);
            if (inten < 0)
                inten = 0;
            else if (inten > 255)
                inten = 255;

            /* Set a pixel */
            gdImageSetPixel(im, i, j, gray[inten]);
        }
    }

    /* Horizontally centered label at the bottom of the picture */
    gdImageString(im, gdFontGetLarge(), im->sx/2 - (strlen(label)*gdFontGetLarge()->w/2), 
      im->sy - gdFontGetLarge()->h, (unsigned char *)label, red);

    /* Open the graphics file. "wb" means "write binary", important
    under MSDOS, harmless under Unix. */

    if ((fp = fopen(filename, "wb")) == NULL) {
        printf("Unable to open the snapshot file %s for write. Exiting\n", filename);
        exit(0);
    } 

    /* Output the image to the disk file in gif format. */
    gdImageGif(im, fp);

    /* Destroy the image in memory. */
    gdImageDestroy(im);

    (void) fclose(fp);

}