rpng-x.c

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/*---------------------------------------------------------------------------

   rpng - simple PNG display program                               rpng-x.c

   This program decodes and displays PNG images, with gamma correction and
   optionally with a user-specified background color (in case the image has
   transparency).  It is very nearly the most basic PNG viewer possible.
   This version is for the X Window System (tested by author under Unix and
   by Martin Zinser under OpenVMS; may work under OS/2 with some tweaking).

   to do:
    - 8-bit (colormapped) X support
    - use %.1023s to simplify truncation of title-bar string?

  ---------------------------------------------------------------------------

   Changelog:
    - 1.01:  initial public release
    - 1.02:  modified to allow abbreviated options; fixed long/ulong mis-
              match; switched to png_jmpbuf() macro
    - 1.10:  added support for non-default visuals; fixed X pixel-conversion
    - 1.11:  added extra set of parentheses to png_jmpbuf() macro; fixed
              command-line parsing bug
    - 1.12:  fixed some small X memory leaks (thanks to Fran鏾is Petitjean)
    - 1.13:  fixed XFreeGC() crash bug (thanks to Patrick Welche)
    - 1.14:  added support for X resources (thanks to Gerhard Niklasch)
    - 2.00:  dual-licensed (added GNU GPL)

  ---------------------------------------------------------------------------

      Copyright (c) 1998-2007 Greg Roelofs.  All rights reserved.

      This software is provided "as is," without warranty of any kind,
      express or implied.  In no event shall the author or contributors
      be held liable for any damages arising in any way from the use of
      this software.

      The contents of this file are DUAL-LICENSED.  You may modify and/or
      redistribute this software according to the terms of one of the
      following two licenses (at your option):


      LICENSE 1 ("BSD-like with advertising clause"):

      Permission is granted to anyone to use this software for any purpose,
      including commercial applications, and to alter it and redistribute
      it freely, subject to the following restrictions:

      1. Redistributions of source code must retain the above copyright
         notice, disclaimer, and this list of conditions.
      2. Redistributions in binary form must reproduce the above copyright
         notice, disclaimer, and this list of conditions in the documenta-
         tion and/or other materials provided with the distribution.
      3. All advertising materials mentioning features or use of this
         software must display the following acknowledgment:

            This product includes software developed by Greg Roelofs
            and contributors for the book, "PNG: The Definitive Guide,"
            published by O'Reilly and Associates.


      LICENSE 2 (GNU GPL v2 or later):

      This program is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.

      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software Foundation,
      Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

  ---------------------------------------------------------------------------*/

#define PROGNAME  "rpng-x"
#define LONGNAME  "Simple PNG Viewer for X"
#define VERSION   "2.00 of 2 June 2007"
#define RESNAME   "rpng"	/* our X resource application name */
#define RESCLASS  "Rpng"	/* our X resource class name */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xos.h>
#include <X11/keysym.h>

/* #define DEBUG  :  this enables the Trace() macros */

#include "readpng.h"   /* typedefs, common macros, readpng prototypes */


/* could just include png.h, but this macro is the only thing we need
 * (name and typedefs changed to local versions); note that side effects
 * only happen with alpha (which could easily be avoided with
 * "ush acopy = (alpha);") */

#define alpha_composite(composite, fg, alpha, bg) {               \
    ush temp = ((ush)(fg)*(ush)(alpha) +                          \
                (ush)(bg)*(ush)(255 - (ush)(alpha)) + (ush)128);  \
    (composite) = (uch)((temp + (temp >> 8)) >> 8);               \
}


/* local prototypes */
static int  rpng_x_create_window(void);
static int  rpng_x_display_image(void);
static void rpng_x_cleanup(void);
static int  rpng_x_msb(ulg u32val);


static char titlebar[1024], *window_name = titlebar;
static char *appname = LONGNAME;
static char *icon_name = PROGNAME;
static char *res_name = RESNAME;
static char *res_class = RESCLASS;
static char *filename;
static FILE *infile;

static char *bgstr;
static uch bg_red=0, bg_green=0, bg_blue=0;

static double display_exponent;

static ulg image_width, image_height, image_rowbytes;
static int image_channels;
static uch *image_data;

/* X-specific variables */
static char *displayname;
static XImage *ximage;
static Display *display;
static int depth;
static Visual *visual;
static XVisualInfo *visual_list;
static int RShift, GShift, BShift;
static ulg RMask, GMask, BMask;
static Window window;
static GC gc;
static Colormap colormap;

static int have_nondefault_visual = FALSE;
static int have_colormap = FALSE;
static int have_window = FALSE;
static int have_gc = FALSE;
/*
ulg numcolors=0, pixels[256];
ush reds[256], greens[256], blues[256];
 */




int main(int argc, char **argv)
{
#ifdef sgi
    char tmpline[80];
#endif
    char *p;
    int rc, alen, flen;
    int error = 0;
    int have_bg = FALSE;
    double LUT_exponent;               /* just the lookup table */
    double CRT_exponent = 2.2;         /* just the monitor */
    double default_display_exponent;   /* whole display system */
    XEvent e;
    KeySym k;


    displayname = (char *)NULL;
    filename = (char *)NULL;


    /* First set the default value for our display-system exponent, i.e.,
     * the product of the CRT exponent and the exponent corresponding to
     * the frame-buffer's lookup table (LUT), if any.  This is not an
     * exhaustive list of LUT values (e.g., OpenStep has a lot of weird
     * ones), but it should cover 99% of the current possibilities. */

#if defined(NeXT)
    LUT_exponent = 1.0 / 2.2;
    /*
    if (some_next_function_that_returns_gamma(&next_gamma))
        LUT_exponent = 1.0 / next_gamma;
     */
#elif defined(sgi)
    LUT_exponent = 1.0 / 1.7;
    /* there doesn't seem to be any documented function to get the
     * "gamma" value, so we do it the hard way */
    infile = fopen("/etc/config/system.glGammaVal", "r");
    if (infile) {
        double sgi_gamma;

        fgets(tmpline, 80, infile);
        fclose(infile);
        sgi_gamma = atof(tmpline);
        if (sgi_gamma > 0.0)
            LUT_exponent = 1.0 / sgi_gamma;
    }
#elif defined(Macintosh)
    LUT_exponent = 1.8 / 2.61;
    /*
    if (some_mac_function_that_returns_gamma(&mac_gamma))
        LUT_exponent = mac_gamma / 2.61;
     */
#else
    LUT_exponent = 1.0;   /* assume no LUT:  most PCs */
#endif

    /* the defaults above give 1.0, 1.3, 1.5 and 2.2, respectively: */
    default_display_exponent = LUT_exponent * CRT_exponent;


    /* If the user has set the SCREEN_GAMMA environment variable as suggested
     * (somewhat imprecisely) in the libpng documentation, use that; otherwise
     * use the default value we just calculated.  Either way, the user may
     * override this via a command-line option. */

    if ((p = getenv("SCREEN_GAMMA")) != NULL)
        display_exponent = atof(p);
    else
        display_exponent = default_display_exponent;


    /* Now parse the command line for options and the PNG filename. */

    while (*++argv && !error) {
        if (!strncmp(*argv, "-display", 2)) {
            if (!*++argv)
                ++error;
            else
                displayname = *argv;
        } else if (!strncmp(*argv, "-gamma", 2)) {
            if (!*++argv)
                ++error;
            else {
                display_exponent = atof(*argv);
                if (display_exponent <= 0.0)
                    ++error;
            }
        } else if (!strncmp(*argv, "-bgcolor", 2)) {
            if (!*++argv)
                ++error;
            else {
                bgstr = *argv;
                if (strlen(bgstr) != 7 || bgstr[0] != '#')
                    ++error; 
                else 
                    have_bg = TRUE;
            }
        } else {
            if (**argv != '-') {
                filename = *argv;
                if (argv[1])   /* shouldn't be any more args after filename */
                    ++error;
            } else
                ++error;   /* not expecting any other options */
        }
    }

    if (!filename) {
        ++error;
    } else if (!(infile = fopen(filename, "rb"))) {
        fprintf(stderr, PROGNAME ":  can't open PNG file [%s]\n", filename);
        ++error;
    } else {
        if ((rc = readpng_init(infile, &image_width, &image_height)) != 0) {
            switch (rc) {
                case 1:
                    fprintf(stderr, PROGNAME
                      ":  [%s] is not a PNG file: incorrect signature\n",
                      filename);
                    break;
                case 2:
                    fprintf(stderr, PROGNAME
                      ":  [%s] has bad IHDR (libpng longjmp)\n",
                      filename);
                    break;
                case 4:
                    fprintf(stderr, PROGNAME ":  insufficient memory\n");
                    break;
                default:
                    fprintf(stderr, PROGNAME
                      ":  unknown readpng_init() error\n");
                    break;
            }
            ++error;
        } else {
            display = XOpenDisplay(displayname);
            if (!display) {
                readpng_cleanup(TRUE);
                fprintf(stderr, PROGNAME ":  can't open X display [%s]\n",
                  displayname? displayname : "default");
                ++error;
            }
        }
        if (error)
            fclose(infile);
    }


    /* usage screen */

    if (error) {
        fprintf(stderr, "\n%s %s:  %s\n", PROGNAME, VERSION, appname);
        readpng_version_info();
        fprintf(stderr, "\n"
          "Usage:  %s [-display xdpy] [-gamma exp] [-bgcolor bg] file.png\n"
          "    xdpy\tname of the target X display (e.g., ``hostname:0'')\n"
          "    exp \ttransfer-function exponent (``gamma'') of the display\n"
          "\t\t  system in floating-point format (e.g., ``%.1f''); equal\n"
          "\t\t  to the product of the lookup-table exponent (varies)\n"
          "\t\t  and the CRT exponent (usually 2.2); must be positive\n"
          "    bg  \tdesired background color in 7-character hex RGB format\n"
          "\t\t  (e.g., ``#ff7700'' for orange:  same as HTML colors);\n"
          "\t\t  used with transparent images\n"
          "\nPress Q, Esc or mouse button 1 (within image window, after image\n"
          "is displayed) to quit.\n"
          "\n", PROGNAME, default_display_exponent);
        exit(1);
    }


    /* set the title-bar string, but make sure buffer doesn't overflow */

    alen = strlen(appname);
    flen = strlen(filename);
    if (alen + flen + 3 > 1023)
        sprintf(titlebar, "%s:  ...%s", appname, filename+(alen+flen+6-1023));
    else
        sprintf(titlebar, "%s:  %s", appname, filename);


    /* if the user didn't specify a background color on the command line,
     * check for one in the PNG file--if not, the initialized values of 0
     * (black) will be used */

    if (have_bg) {
        unsigned r, g, b;   /* this approach quiets compiler warnings */

        sscanf(bgstr+1, "%2x%2x%2x", &r, &g, &b);
        bg_red   = (uch)r;
        bg_green = (uch)g;
        bg_blue  = (uch)b;
    } else if (readpng_get_bgcolor(&bg_red, &bg_green, &bg_blue) > 1) {
        readpng_cleanup(TRUE);
        fprintf(stderr, PROGNAME
          ":  libpng error while checking for background color\n");
        exit(2);
    }


    /* do the basic X initialization stuff, make the window and fill it
     * with the background color */

    if (rpng_x_create_window())
        exit(2);


    /* decode the image, all at once */

    Trace((stderr, "calling readpng_get_image()\n"))
    image_data = readpng_get_image(display_exponent, &image_channels,
      &image_rowbytes);
    Trace((stderr, "done with readpng_get_image()\n"))


    /* done with PNG file, so clean up to minimize memory usage (but do NOT
     * nuke image_data!) */

    readpng_cleanup(FALSE);
    fclose(infile);

    if (!image_data) {
        fprintf(stderr, PROGNAME ":  unable to decode PNG image\n");
        exit(3);
    }


    /* display image (composite with background if requested) */

    Trace((stderr, "calling rpng_x_display_image()\n"))
    if (rpng_x_display_image()) {
        free(image_data);
        exit(4);
    }
    Trace((stderr, "done with rpng_x_display_image()\n"))


    /* wait for the user to tell us when to quit */

    printf(
      "Done.  Press Q, Esc or mouse button 1 (within image window) to quit.\n");
    fflush(stdout);

    do
        XNextEvent(display, &e);
    while (!(e.type == ButtonPress && e.xbutton.button == Button1) &&
           !(e.type == KeyPress &&    /*  v--- or 1 for shifted keys */
             ((k = XLookupKeysym(&e.xkey, 0)) == XK_q || k == XK_Escape) ));


    /* OK, we're done:  clean up all image and X resources and go away */

    rpng_x_cleanup();

    return 0;
}





static int rpng_x_create_window(void)
{
    uch *xdata;
    int need_colormap = FALSE;
    int screen, pad;
    ulg bg_pixel = 0L;
    ulg attrmask;
    Window root;
    XEvent e;
    XGCValues gcvalues;
    XSetWindowAttributes attr;
    XTextProperty windowName, *pWindowName = &windowName;
    XTextProperty iconName, *pIconName = &iconName;
    XVisualInfo visual_info;
    XSizeHints *size_hints;
    XWMHints *wm_hints;
    XClassHint *class_hints;


    screen = DefaultScreen(display);
    depth = DisplayPlanes(display, screen);
    root = RootWindow(display, screen);

#ifdef DEBUG
    XSynchronize(display, True);
#endif

#if 0
/* GRR:  add 8-bit support */