pngdriver/read_ppm.c

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/*!
  \file lib/pngdriver/read_ppm.c

  \brief GRASS png display driver - read image (lower level functions)

  (C) 2007-2014 by Glynn Clements and the GRASS Development Team
  
  This program is free software under the GNU General Public License
  (>=v2). Read the file COPYING that comes with GRASS for details.
  
  \author Glynn Clements
*/


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

#include <grass/gis.h>
#include "pngdriver.h"

void read_ppm(void)
{
    FILE *input;
    int x, y;
    int i_width, i_height, maxval;
    unsigned int rgb_mask = png_get_color(255, 255, 255, 0);
    unsigned int *p;

    if (!png.true_color)
        G_fatal_error("PNG: cannot use PPM/PGM with indexed color");

    input = fopen(png.file_name, "rb");
    if (!input)
        G_fatal_error("PNG: couldn't open input file %s", png.file_name);

    if (fscanf(input, "P6 %d %d %d", &i_width, &i_height, &maxval) != 3)
        G_fatal_error("PNG: invalid input file %s", png.file_name);

    fgetc(input);

    if (i_width != png.width || i_height != png.height)
        G_fatal_error
            ("PNG: input file has incorrect dimensions: expected: %dx%d got: %dx%d",
             png.width, png.height, i_width, i_height);

    for (y = 0, p = png.grid; y < png.height; y++) {
        for (x = 0; x < png.width; x++, p++) {
            unsigned int c = *p;

            int r = fgetc(input);
            int g = fgetc(input);
            int b = fgetc(input);

            r = r * 255 / maxval;
            g = g * 255 / maxval;
            b = b * 255 / maxval;

            c &= ~rgb_mask;
            c |= png_get_color(r, g, b, 0);

            *p = c;
        }
    }

    fclose(input);
}

void read_pgm(void)
{
    char *mask_name = G_store(png.file_name);
    FILE *input;
    int x, y;
    int i_width, i_height, maxval;
    unsigned int rgb_mask = png_get_color(255, 255, 255, 0);
    unsigned int *p;

    if (!png.true_color)
        G_fatal_error("PNG: cannot use PPM/PGM with indexed color");

    mask_name[strlen(mask_name) - 2] = 'g';

    input = fopen(mask_name, "rb");
    if (!input)
        G_fatal_error("PNG: couldn't open input mask file %s", mask_name);

    if (fscanf(input, "P5 %d %d %d", &i_width, &i_height, &maxval) != 3)
        G_fatal_error("PNG: invalid input mask file %s", mask_name);

    fgetc(input);

    if (i_width != png.width || i_height != png.height)
        G_fatal_error
            ("PNG: input mask file has incorrect dimensions: expected: %dx%d got: %dx%d",
             png.width, png.height, i_width, i_height);

    G_free(mask_name);

    for (y = 0, p = png.grid; y < png.height; y++) {
        for (x = 0; x < png.width; x++, p++) {
            unsigned int c = *p;

            int k = fgetc(input);

            k = k * 255 / maxval;

            c &= rgb_mask;
            c |= png_get_color(0, 0, 0, 255 - k);

            *p = c;
        }
    }

    fclose(input);
}