mirror of
https://git.code.sf.net/p/libpng/code.git
synced 2025-07-10 18:04:09 +02:00
bdbbcaa457
Improve and modernize png2pnm.c: * Remove the explicit reading of the input PNG file signature. Libpng is now able to read it, check it, and issue an appropriate error message in case of magic number mismatch or file corruption. (See the function `png_read_sig`.) * Remove the explicit allocation and dealocation of the image data. Libpng is now able to manage all the image data automatically. (See the function `png_read_png`.) * Specify the needed image transformations without a-priori checking the image type for applicability. * Use the `png_set_expand_gray_1_2_4_to_8` transformation. Since libpng version 1.2.9, this transformation (if needed) must be enabled separately from `png_set_expand`. Improve and modernize pnm2png.c: * Modify the allocation of image data, in order to match libpng's internal allocation model. * Transfer the ownership of the image data from the `pnm2png` function to libpng, which will manage and dealocate it at the right time. (See the functions `png_set_image_rows` and `png_data_freer`.) Refactor, clean up, etc.
374 lines
9.7 KiB
C
374 lines
9.7 KiB
C
/*
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* png2pnm.c --- conversion from PNG-file to PGM/PPM-file
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* copyright (C) 1999-2019 by Willem van Schaik <willem at schaik dot com>
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*
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* This software is released under the MIT license. For conditions of
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* distribution and use, see the LICENSE file part of this package.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#ifndef BOOL
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#define BOOL unsigned char
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#endif
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#ifndef TRUE
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#define TRUE ((BOOL) 1)
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#endif
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#ifndef FALSE
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#define FALSE ((BOOL) 0)
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#endif
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#include "png.h"
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/* function prototypes */
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int main (int argc, char *argv[]);
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void usage ();
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BOOL png2pnm (FILE *png_file, FILE *pnm_file, FILE *alpha_file,
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BOOL raw, BOOL alpha);
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BOOL png2pnm_internal (png_struct *png_ptr, png_info *info_ptr,
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FILE *pnm_file, FILE *alpha_file,
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BOOL raw, BOOL alpha);
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/*
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* main
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*/
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int main (int argc, char *argv[])
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{
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FILE *fp_rd = stdin;
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FILE *fp_wr = stdout;
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FILE *fp_al = NULL;
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BOOL raw = TRUE;
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BOOL alpha = FALSE;
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int argi;
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for (argi = 1; argi < argc; argi++)
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{
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if (argv[argi][0] == '-')
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{
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switch (argv[argi][1])
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{
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case 'n':
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raw = FALSE;
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break;
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case 'r':
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raw = TRUE;
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break;
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case 'a':
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alpha = TRUE;
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argi++;
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if ((fp_al = fopen (argv[argi], "wb")) == NULL)
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{
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fprintf (stderr, "PNM2PNG\n");
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fprintf (stderr, "Error: cannot create alpha-channel file %s\n",
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argv[argi]);
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exit (1);
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}
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break;
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case 'h':
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case '?':
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usage ();
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exit (0);
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break;
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default:
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fprintf (stderr, "PNG2PNM\n");
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fprintf (stderr, "Error: unknown option %s\n", argv[argi]);
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usage ();
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exit (1);
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break;
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} /* end switch */
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}
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else if (fp_rd == stdin)
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{
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if ((fp_rd = fopen (argv[argi], "rb")) == NULL)
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{
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fprintf (stderr, "PNG2PNM\n");
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fprintf (stderr, "Error: file %s does not exist\n", argv[argi]);
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exit (1);
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}
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}
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else if (fp_wr == stdout)
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{
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if ((fp_wr = fopen (argv[argi], "wb")) == NULL)
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{
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fprintf (stderr, "PNG2PNM\n");
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fprintf (stderr, "Error: cannot create file %s\n", argv[argi]);
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exit (1);
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}
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}
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else
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{
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fprintf (stderr, "PNG2PNM\n");
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fprintf (stderr, "Error: too many parameters\n");
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usage ();
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exit (1);
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}
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} /* end for */
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#if defined(O_BINARY) && (O_BINARY != 0)
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/* set stdin/stdout if required to binary */
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if (fp_rd == stdin)
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setmode (fileno (stdin), O_BINARY);
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if ((raw) && (fp_wr == stdout))
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setmode (fileno (stdout), O_BINARY);
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#endif
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/* call the conversion program itself */
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if (png2pnm (fp_rd, fp_wr, fp_al, raw, alpha) == FALSE)
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{
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fprintf (stderr, "PNG2PNM\n");
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fprintf (stderr, "Error: unsuccessful conversion of PNG-image\n");
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exit (1);
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}
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/* close input file */
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fclose (fp_rd);
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/* close output file */
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fclose (fp_wr);
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/* close alpha file */
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if (alpha)
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fclose (fp_al);
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return 0;
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}
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/*
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* usage
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*/
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void usage ()
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{
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fprintf (stderr, "PNG2PNM\n");
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fprintf (stderr, " by Willem van Schaik, 1999\n");
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fprintf (stderr, "Usage: png2pnm [options] <file>.png [<file>.pnm]\n");
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fprintf (stderr, " or: ... | png2pnm [options]\n");
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fprintf (stderr, "Options:\n");
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fprintf (stderr,
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" -r[aw] write pnm-file in binary format (P4/P5/P6) (default)\n");
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fprintf (stderr, " -n[oraw] write pnm-file in ascii format (P1/P2/P3)\n");
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fprintf (stderr,
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" -a[lpha] <file>.pgm write PNG alpha channel as pgm-file\n");
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fprintf (stderr, " -h | -? print this help-information\n");
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}
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/*
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* png2pnm
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*/
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BOOL png2pnm (FILE *png_file, FILE *pnm_file, FILE *alpha_file,
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BOOL raw, BOOL alpha)
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{
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png_struct *png_ptr;
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png_info *info_ptr;
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BOOL ret;
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/* initialize the libpng structures for reading from png_file */
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png_ptr = png_create_read_struct (png_get_libpng_ver(NULL),
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NULL, NULL, NULL);
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if (!png_ptr)
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return FALSE; /* out of memory */
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info_ptr = png_create_info_struct (png_ptr);
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if (!info_ptr)
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{
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png_destroy_read_struct (&png_ptr, NULL, NULL);
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return FALSE; /* out of memory */
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}
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if (setjmp (png_jmpbuf (png_ptr)))
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{
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png_destroy_read_struct (&png_ptr, &info_ptr, NULL);
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return FALSE; /* generic libpng error */
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}
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png_init_io (png_ptr, png_file);
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/* do the actual conversion */
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ret = png2pnm_internal (png_ptr, info_ptr, pnm_file, alpha_file, raw, alpha);
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/* clean up the libpng structures and their internally-managed data */
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png_destroy_read_struct (&png_ptr, &info_ptr, NULL);
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return ret;
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}
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/*
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* png2pnm_internal
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*/
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BOOL png2pnm_internal (png_struct *png_ptr, png_info *info_ptr,
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FILE *pnm_file, FILE *alpha_file,
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BOOL raw, BOOL alpha)
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{
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png_byte **row_pointers;
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png_byte *pix_ptr;
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png_uint_32 width;
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png_uint_32 height;
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int bit_depth;
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int channels;
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int color_type;
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int alpha_present;
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png_uint_32 row, col, i;
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long dep_16;
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/* set up the image transformations that are necessary for the PNM format */
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/* set up (if applicable) the expansion of paletted images to full-color rgb,
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* and the expansion of transparency maps to full alpha-channel */
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png_set_expand (png_ptr);
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/* set up (if applicable) the expansion of grayscale images to bit-depth 8 */
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png_set_expand_gray_1_2_4_to_8 (png_ptr);
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#ifdef NJET /* FIXME */
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/* downgrade 16-bit images to 8-bit */
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if (bit_depth == 16)
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png_set_strip_16 (png_ptr);
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/* transform grayscale images into full-color */
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if (color_type == PNG_COLOR_TYPE_GRAY ||
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color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
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png_set_gray_to_rgb (png_ptr);
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/* only if file has a file gamma, we do a correction */
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if (png_get_gAMA (png_ptr, info_ptr, &file_gamma))
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png_set_gamma (png_ptr, (double) 2.2, file_gamma);
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#endif
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/* read the image file, with all of the above image transforms applied */
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png_read_png (png_ptr, info_ptr, 0, NULL);
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/* get the image size, bit-depth and color-type */
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png_get_IHDR (png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
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NULL, NULL, NULL);
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/* calculate the number of channels and store alpha-presence */
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if (color_type == PNG_COLOR_TYPE_GRAY)
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channels = 1;
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else if (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
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channels = 2;
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else if (color_type == PNG_COLOR_TYPE_RGB)
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channels = 3;
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else if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
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channels = 4;
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else
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channels = 0; /* should never happen */
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alpha_present = (channels - 1) % 2;
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/* check if alpha is expected to be present in file */
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if (alpha && !alpha_present)
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{
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fprintf (stderr, "PNG2PNM\n");
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fprintf (stderr, "Warning: no alpha channel in PNG file\n");
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return FALSE;
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}
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/* get address of internally-allocated image data */
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row_pointers = png_get_rows (png_ptr, info_ptr);
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/* write header of PNM file */
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if ((color_type == PNG_COLOR_TYPE_GRAY) ||
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(color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
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{
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fprintf (pnm_file, "%s\n", (raw) ? "P5" : "P2");
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fprintf (pnm_file, "%d %d\n", (int) width, (int) height);
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fprintf (pnm_file, "%ld\n", ((1L << (int) bit_depth) - 1L));
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}
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else if ((color_type == PNG_COLOR_TYPE_RGB) ||
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(color_type == PNG_COLOR_TYPE_RGB_ALPHA))
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{
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fprintf (pnm_file, "%s\n", (raw) ? "P6" : "P3");
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fprintf (pnm_file, "%d %d\n", (int) width, (int) height);
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fprintf (pnm_file, "%ld\n", ((1L << (int) bit_depth) - 1L));
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}
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/* write header of PGM file with alpha channel */
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if ((alpha) &&
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((color_type == PNG_COLOR_TYPE_GRAY_ALPHA) ||
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(color_type == PNG_COLOR_TYPE_RGB_ALPHA)))
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{
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fprintf (alpha_file, "%s\n", (raw) ? "P5" : "P2");
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fprintf (alpha_file, "%d %d\n", (int) width, (int) height);
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fprintf (alpha_file, "%ld\n", ((1L << (int) bit_depth) - 1L));
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}
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/* write data to PNM file */
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for (row = 0; row < height; row++)
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{
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pix_ptr = row_pointers[row];
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for (col = 0; col < width; col++)
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{
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for (i = 0; i < (png_uint_32) (channels - alpha_present); i++)
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{
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if (raw)
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{
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fputc ((int) *pix_ptr++, pnm_file);
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if (bit_depth == 16)
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fputc ((int) *pix_ptr++, pnm_file);
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}
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else
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{
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if (bit_depth == 16)
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{
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dep_16 = ((long) *pix_ptr++) << 8;
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dep_16 += ((long) *pix_ptr++);
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fprintf (pnm_file, "%ld ", dep_16);
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}
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else
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{
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fprintf (pnm_file, "%ld ", (long) *pix_ptr++);
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}
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}
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}
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if (alpha_present)
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{
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if (!alpha)
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{
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/* skip the alpha-channel */
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pix_ptr++;
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if (bit_depth == 16)
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pix_ptr++;
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}
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else
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{
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/* output the alpha-channel as pgm file */
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if (raw)
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{
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fputc ((int) *pix_ptr++, alpha_file);
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if (bit_depth == 16)
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fputc ((int) *pix_ptr++, alpha_file);
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}
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else
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{
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if (bit_depth == 16)
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{
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dep_16 = ((long) *pix_ptr++) << 8;
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dep_16 += ((long) *pix_ptr++);
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fprintf (alpha_file, "%ld ", dep_16);
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}
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else
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{
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fprintf (alpha_file, "%ld ", (long) *pix_ptr++);
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}
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}
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}
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} /* end if alpha_present */
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if (!raw)
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if (col % 4 == 3)
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fprintf (pnm_file, "\n");
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} /* end for col */
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if (!raw)
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if (col % 4 != 0)
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fprintf (pnm_file, "\n");
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} /* end for row */
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return TRUE;
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} /* end of source */
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