ppm.cpp

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

#include "pic.h"

/*
 * ppm: subroutines for reading PPM picture files
 *
 * Paul Heckbert	18 Jan 94
 *
 * Michael Garland      17 Jan 96 : Added ppm_write
 */

 /* ppm_get_token: read token from PPM file in stream fp into "char tok[len]" */
char* ppm_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;
}

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

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

/*
 * ppm_read: read a PPM 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* ppm_read(char* file, Pic* opic) {
	FILE* fp;
	char tok[20];
	int nx, ny, pvmax;
	Pic* p;

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

	/* read PPM header */
	if (strcmp(ppm_get_token(fp, tok, sizeof tok), "P6")) {
		fprintf(stderr, "%s not a valid binary PPM file, bad magic#\n", file);
		fclose(fp);
		return 0;
	}
	if (sscanf(ppm_get_token(fp, tok, sizeof tok), "%d", &nx) != 1 ||
		sscanf(ppm_get_token(fp, tok, sizeof tok), "%d", &ny) != 1 ||
		sscanf(ppm_get_token(fp, tok, sizeof tok), "%d", &pvmax) != 1) {
		fprintf(stderr, "%s is not a valid PPM 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, 3, opic);
	printf("reading PPM file %s: %dx%d pixels\n", file, p->nx, p->ny);

	if (fread(p->pix, p->nx * 3, 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 ppm_write(char* file, Pic* pic)
{
	FILE* ppm;

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

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

	/* Always write a raw PPM file */
	fprintf(ppm, "P6 %d %d 255\n", pic->nx, pic->ny);

	if (fwrite(pic->pix, pic->nx * 3, pic->ny, ppm) != pic->ny) {
		fprintf(stderr, "ppm_write: error writing %s\n", file);
		fclose(ppm);
		return FALSE;
	}

	fclose(ppm);
	return TRUE;
}