/*
 * pnm: subroutines for reading PNM picture files (PPM or PGM)
 *
 * Paul Heckbert	18 Jan 94
 *
 * Michael Garland      17 Jan 96 : Added ppm_write
 *
 * Paul Heckbert	27 Oct 98 : added PGM support, renamed ppm->pnm
 */

#include <stdio.h>
#include <sys/types.h>
#include <ctype.h>

#include "pic.h"

/* pnm_get_token: read token from PNM file in stream fp into "char tok[len]" */
char *pnm_get_token(FILE *fp, char *tok, int len) {
    char *t;
    int c;

    for (;;) {			/* skip over whitespace and comments */
	while (isspace(c = getc(fp)));
	if (c!='#') break;
	do c = getc(fp); while (c!='\n' && c!=EOF);	/* gobble comment */
	if (c==EOF) break;
    }

    t = tok;
    if (c!=EOF) {
	do {
	    *t++ = c;
	    c = getc(fp);
	} while (!isspace(c) && c!='#' && c!=EOF && t-tok<len-1);
	if (c=='#') ungetc(c, fp);	/* put '#' back for next time */
    }
    *t = 0;
    return tok;
}

/* pnm_get_size: get size in pixels of PNM picture file */
int pnm_get_size(char *file, int *nx, int *ny) {
    char tok[20];
    FILE *fp;

    if ((fp = fopen(file, "r")) == NULL) {
	fprintf(stderr, "can't read PNM file %s\n", file);
	return 0;
    }
    pnm_get_token(fp, tok, sizeof tok);
    if (strcmp(tok, "P5") && strcmp(tok, "P6")) {
	fprintf(stderr,
	    "%s is not a valid binary PGM or PPM file, bad magic#\n", file);
	fclose(fp);
	return 0;
    }
    if (sscanf(pnm_get_token(fp, tok, sizeof tok), "%d", nx) != 1 ||
	sscanf(pnm_get_token(fp, tok, sizeof tok), "%d", ny) != 1) {
	    fprintf(stderr, "%s is not a valid PNM file: bad size\n", file);
	    fclose(fp);
	    return 0;
    }
    fclose(fp);
    return 1;
}

/*
 * pnm_read: read a PNM file into memory.
 * If opic!=0, then picture is read into opic->pix (after checking that
 * size is sufficient), else a new Pic is allocated.
 * Returns Pic pointer on success, 0 on failure.
 */
Pic *pnm_read(char *file, Pic *opic) {
    FILE *fp;
    char tok[20];
    int nx, ny, bpp, pvmax;
    Pic *p;

    /* open PNM file */
    if ((fp = fopen(file, "r")) == NULL) {
	fprintf(stderr, "can't read PNM file %s\n", file);
	return 0;
    }

    /* read PNM header */
    pnm_get_token(fp, tok, sizeof tok);
    if (strcmp(tok, "P5") && strcmp(tok, "P6")) {
	fprintf(stderr,
	    "%s is not a valid binary PGM or PPM file, bad magic#\n", file);
	fclose(fp);
	return 0;
    }
    bpp = strcmp(tok, "P6") ? 1 : 3;
	/* set bytes per pixel
	 * "P5" is header for PGM (grayscale), "P6" is header for PPM (color)*/
    if (sscanf(pnm_get_token(fp, tok, sizeof tok), "%d", &nx) != 1 ||
	sscanf(pnm_get_token(fp, tok, sizeof tok), "%d", &ny) != 1 ||
	sscanf(pnm_get_token(fp, tok, sizeof tok), "%d", &pvmax) != 1) {
	    fprintf(stderr, "%s is not a valid PNM file: bad size\n", file);
	    fclose(fp);
	    return 0;
    }

    if (pvmax!=255) {
	fprintf(stderr, "%s does not have 8-bit components: pvmax=%d\n",
	    file, pvmax);
	fclose(fp);
	return 0;
    }

    p = pic_alloc(nx, ny, bpp, opic);
    printf("reading PNM file %s: %dx%d pixels, %d byte per pixel\n",
	file, p->nx, p->ny, p->bpp);

    if (fread(p->pix, p->nx*p->bpp, p->ny, fp) != p->ny) {  /* read pixels */
	fprintf(stderr, "premature EOF on file %s\n", file);
	free(p);
	fclose(fp);
	return 0;
    }
    fclose(fp);
    return p;
}

int pnm_write(char *file, Pic *pic)
{
    FILE *pnm;

    if (pic->bpp!=1 && pic->bpp!=3) {
	fprintf(stderr, "pnm_write: can't write %d byte per pixel Pic\n",
	    pic->bpp);
	return FALSE;
    }

    /* Open the file for output */
    pnm = fopen(file, "w");
    if( !pnm )
	return FALSE;

    /* Always write a binary PNM file */
    fprintf(pnm, "P%c %d %d 255\n", pic->bpp==1 ? '5' : '6', pic->nx, pic->ny);
    /* "P5" is header for PGM (grayscale), "P6" is header for PPM (color) */
    
    if (fwrite(pic->pix, pic->nx*pic->bpp, pic->ny, pnm) != pic->ny) {
	fprintf(stderr, "pnm_write: error writing %s\n", file);
	fclose(pnm);
	return FALSE;
    }

    fclose(pnm);
    return TRUE;
}