webpng.c

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/* Bring in the gd library functions */
#include "gd.h"
 
/* Bring in standard I/O and string manipulation functions */
#include <stdio.h>
#include <stdlib.h>     /* for atoi() */
#include <string.h>
 
#ifdef _WIN32
#include <process.h>
int
getpid ()
{
  return _getpid ();
}
#else
#include <unistd.h>     /* for getpid(), unlink() */
#endif
int
main (int argc, char **argv)
{
  FILE *in;
  FILE *out;
  char outFn[20];
  int useStdinStdout = 0;
 
  /* Declare our image pointer */
  gdImagePtr im = 0;
  int i;
  /* We'll clear 'no' once we know the user has made a
     reasonable request. */
  int no = 1;
  /* We'll set 'write' once we know the user's request
     requires that the image be written back to disk. */
  int write = 0;
  /* C programs always get at least one argument; we want at
     least one more (the image), more in practice. */
  if (argc < 2 || !strcmp (argv[1], "--help"))
    {
      no = 1;
      goto usage;
    }
 
  /* The last argument should be the image. Open the file. */
  if (strcmp ("-", argv[argc - 1]) == 0)
    {               /* - is synonymous with STDIN */
      useStdinStdout = 1;
      in = stdin;
    }
  else
    {
      in = fopen (argv[argc - 1], "rb");
    }
  if (!in)
    {
      fprintf (stderr,
           "Error: can't open file %s.\n", argv[argc - 1]);
      exit (1);
    }
  /* Now load the image. */
  im = gdImageCreateFromPng (in);
  fclose (in);
  /* If the load failed, it must not be a PNG file. */
  if (!im)
    {
      fprintf (stderr,
           "Error: %s is not a valid PNG file.\n", argv[argc - 1]);
      exit (1);
    }
  /* Consider each argument in turn. */
  for (i = 1; (i < (argc - 1)); i++)
    {
      /* -i turns on and off interlacing. */
      if (!strcmp (argv[i], "--help"))
    {
      /* Every program should use this for help! :) */
      no = 1;
      goto usage;
    }
      else if (!strcmp (argv[i], "-i"))
    {
      if (i == (argc - 2))
        {
          fprintf (stderr,
               "Error: -i specified without y or n.\n");
          no = 1;
          goto usage;
        }
      if (!strcmp (argv[i + 1], "y"))
        {
          /* Set interlace. */
          gdImageInterlace (im, 1);
        }
      else if (!strcmp (argv[i + 1], "n"))
        {
          /* Clear interlace. */
          gdImageInterlace (im, 0);
        }
      else
        {
          fprintf (stderr,
               "Error: -i specified without y or n.\n");
          no = 1;
          goto usage;
        }
      i++;
      no = 0;
      write = 1;
    }
      else if (!strcmp (argv[i], "-t"))
    {
      /* Set transparent index (or none). */
      int index;
      if (i == (argc - 2))
        {
          fprintf (stderr,
               "Error: -t specified without a color table index.\n");
          no = 1;
          goto usage;
        }
      if (!strcmp (argv[i + 1], "none"))
        {
          /* -1 means not transparent. */
          gdImageColorTransparent (im, -1);
        }
      else
        {
          /* OK, get an integer and set the index. */
          index = atoi (argv[i + 1]);
          gdImageColorTransparent (im, index);
        }
      i++;
      write = 1;
      no = 0;
    }
      else if (!strcmp (argv[i], "-l"))
    {
      /* List the colors in the color table. */
      int j;
      if (!im->trueColor)
        {
          /* Tabs used below. */
          printf ("Index  Red Green   Blue Alpha\n");
          for (j = 0; (j < gdImageColorsTotal (im)); j++)
        {
          /* Use access macros to learn colors. */
          printf ("%d %d  %d  %d  %d\n",
              j,
              gdImageRed (im, j),
              gdImageGreen (im, j),
              gdImageBlue (im, j),
              gdImageAlpha (im, j));
        }
        }
      else
        {
          printf ("Truecolor image, no palette entries to list.\n");
        }
      no = 0;
    }
      else if (!strcmp (argv[i], "-d"))
    {
      /* Output dimensions, etc. */
      int t;
      printf ("Width: %d Height: %d Colors: %d\n",
          gdImageSX (im), gdImageSY (im),
          gdImageColorsTotal (im));
      t = gdImageGetTransparent (im);
      if (t != (-1))
        {
                printf ("First 100%% transparent index: %d\n", t);
        }
      else
        {
          /* -1 means the image is not transparent. */
                printf ("First 100%% transparent index: none\n");
        }
      if (gdImageGetInterlaced (im))
        {
          printf ("Interlaced: yes\n");
        }
      else
        {
          printf ("Interlaced: no\n");
        }
      no = 0;
    }
        else if (!strcmp(argv[i], "-a"))
        {
            int maxx, maxy, x, y, alpha, pix, nalpha = 0;
 
            maxx = gdImageSX(im);
            maxy = gdImageSY(im);
 
            printf("alpha channel information:\n");
 
            if (im->trueColor) {
                for (y = 0; y < maxy; y++)  {
                    for (x = 0; x < maxx; x++)  {
                        pix = gdImageGetPixel(im, x, y);
                        alpha = gdTrueColorGetAlpha(pix);
 
                        if (alpha > gdAlphaOpaque) {
                            /* Use access macros to learn colors. */
                            printf ("%d   %d  %d  %d\n",
                                    gdTrueColorGetRed(pix),
                                    gdTrueColorGetGreen(pix),
                                    gdTrueColorGetBlue(pix),
                                    alpha);
                            nalpha++;
                        }
 
                    }
                }
            }
            else
                printf("NOT a true color image\n");
            no = 0;
            printf("%d alpha channels\n", nalpha);
 
        }
      else
    {
      fprintf (stderr, "Unknown argument: %s\n", argv[i]);
      break;
    }
    }
usage:
  if (no)
    {
      /* If the command failed, output an explanation. */
      fprintf (stderr,
      "Usage: webpng [-i y|n ] [-l] [-t index|none ] [-d] pngname.png\n"
 
           "  -i [y|n]   Turns on/off interlace\n"
           "  -l         Prints the table of color indexes\n"
           "  -t [index] Set the transparent color to the specified index (0-255 or \"none\")\n"
           "  -d         Reports the dimensions and other characteristics of the image.\n"
                "  -a         Prints all alpha channels that are not 100%% opaque.\n"
           "\n"
           "If you specify '-' as the input file, stdin/stdout will be used input/output.\n"
    );
    }
  if (write)
    {
      if (useStdinStdout)
    {
      out = stdout;
    }
      else
    {
      /* Open a temporary file. */
 
      /* "temp.tmp" is not good temporary filename. */
      snprintf (outFn, sizeof(outFn), "webpng.tmp%d", getpid ());
      out = fopen (outFn, "wb");
 
      if (!out)
        {
          fprintf (stderr,
               "Unable to write to %s -- exiting\n", outFn);
          exit (1);
        }
    }
 
      /* Write the new PNG. */
      gdImagePng (im, out);
 
      if (!useStdinStdout)
    {
      fclose (out);
      /* Erase the old PNG. */
      unlink (argv[argc - 1]);
      /* Rename the new to the old. */
      if (rename (outFn, argv[argc - 1]) != 0)
        {
          perror ("rename");
          exit (1);
        }
    }
    }
  /* Delete the image from memory. */
  if (im)
    {
      gdImageDestroy (im);
    }
  /* All's well that ends well. */
  return 0;
}