/home/carolina/workspace/spvolren_cpu/ppm.c

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/*
 * Copyright (c) 2005  Institute for Visualization and Interactive
 * Systems, University of Stuttgart, Germany
 *
 * This source code is distributed as part of the single-pass volume
 * rendering project. Details about this project can be found on the
 * project web page at http://www.vis.uni-stuttgart.de/eng/research/
 * fields/current/spvolren. This file may be distributed, modified,
 * and used free of charge as long as this copyright notice is
 * included in its original form. Commercial use is strictly
 * prohibited.
 *
 * Filename: ppm.c
 * 
 */

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

#include "ppm.h"

#define MAGIC_NUMBER "P6"

static void readToken(FILE *fp, char *token)
{
        int comment = 0;
        char c;

        do {
                if (fread(&c, 1, 1, fp) != 1) {
                        perror("reading token failed");
                        exit(1);
                }
                if (c == '\n') {
                        comment = 0;
                } else if (c == '#') {
                        comment = 1;
                }
        } while (isspace(c) || comment);

        *token++ = c;

        do {
                if (fread(&c, 1, 1, fp) != 1) {
                        perror("reading token failed");
                        exit(1);
                }
                *token++ = c;
        } while (! isspace(c));

        *--token = '\0';
}

void ppmRead(char *filename, PPMFile *ppmFile)
{
        char token[100], msg[100];
        int dataSize;
        FILE *fp;
        
        if (! (fp = fopen(filename, "rb"))) {
                sprintf(msg, "opening image file \"%s\" failed", filename);
                perror(msg);
                exit(1);
        }

        /* Read magic number */
        readToken(fp, token);
        if (strcmp(MAGIC_NUMBER, token)) {
                fprintf(stderr, "invalid magic number: %s\n", token);
                exit(1);
        }

        /* Read dimensions */
        readToken(fp, token);
        if (sscanf(token, "%i", &ppmFile->width) != 1) {
                fprintf(stderr, "invalid width: %s\n", token);
                exit(1);
        }
        readToken(fp, token);
        if (sscanf(token, "%i", &ppmFile->height) != 1) {
                fprintf(stderr, "invalid height: %s\n", token);
                exit(1);
        }

        /* Allocate memory for image data */
        dataSize = ppmFile->width * ppmFile->height * 3;
        if (! (ppmFile->data = (unsigned char *)malloc(dataSize))) {
                fprintf(stderr, "not enough memory for image data\n");
                exit(1);
        }

        /* Read maximum value */
        readToken(fp, token);
        if (sscanf(token, "%i", &ppmFile->maxVal) != 1) {
                fprintf(stderr, "invalid maximum value: %s\n", token);
                exit(1);
        }

        /* Read image data */
        if (fread(ppmFile->data, dataSize, 1, fp) != 1) {
                perror("reading image data failed");
                exit(1);
        }

        fclose(fp);
}

void ppmWrite(char *filename, PPMFile *ppmFile)
{
        int i, dataSize, maxVal;
        FILE *fp;

        if (! (fp = fopen(filename, "wb")) == -1) {
                perror("opening image file failed");
                exit(1);
        }

        /* Write magic number */
        fprintf(fp, "%s\n", MAGIC_NUMBER);

        /* Write dimensions */
        fprintf(fp, "%i %i\n", ppmFile->width, ppmFile->height); 

        /* Write maximum value */
        dataSize = ppmFile->width * ppmFile->height * 3;
        maxVal = 0;
        for (i = 0; i < dataSize; i++) {
                if (ppmFile->data[i] > maxVal) {
                        maxVal = ppmFile->data[i];
                }
        }
        fprintf(fp, "%i\n", maxVal);

        /* Write image data */
        if (fwrite(ppmFile->data, dataSize, 1, fp) != 1) {
                fprintf(stderr, "writing image data failed\n");
                exit(1);
        }

        fclose(fp);
}

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