rpng2-x.c

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        sscanf(bgstr+1, "%2x%2x%2x", &r, &g, &b);
        rpng2_info.bg_red   = (uch)r;
        rpng2_info.bg_green = (uch)g;
        rpng2_info.bg_blue  = (uch)b;
    } else
        rpng2_info.need_bgcolor = TRUE;

    rpng2_info.done = FALSE;
    rpng2_info.mainprog_init = rpng2_x_init;
    rpng2_info.mainprog_display_row = rpng2_x_display_row;
    rpng2_info.mainprog_finish_display = rpng2_x_finish_display;


    /* OK, this is the fun part:  call readpng2_decode_data() at the start of
     * the loop to deal with our first buffer of data (read in above to verify
     * that the file is a PNG image), then loop through the file and continue
     * calling the same routine to handle each chunk of data.  It in turn
     * passes the data to libpng, which will invoke one or more of our call-
     * backs as decoded data become available.  We optionally call sleep() for
     * one second per iteration to simulate downloading the image via an analog
     * modem. */

    for (;;) {
        Trace((stderr, "about to call readpng2_decode_data()\n"))
        if (readpng2_decode_data(&rpng2_info, inbuf, incount))
            ++error;
        Trace((stderr, "done with readpng2_decode_data()\n"))
        if (error || feof(infile) || rpng2_info.done)
            break;
        if (timing)
            sleep(1);
        incount = fread(inbuf, 1, INBUFSIZE, infile);
    }


    /* clean up PNG stuff and report any decoding errors */

    fclose(infile);
    Trace((stderr, "about to call readpng2_cleanup()\n"))
    readpng2_cleanup(&rpng2_info);

    if (error) {
        fprintf(stderr, PROGNAME ":  libpng error while decoding PNG image\n");
        exit(3);
    }


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

    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) ));


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

    Trace((stderr, "about to call rpng2_x_cleanup()\n"))
    rpng2_x_cleanup();

    return 0;
}





/* this function is called by readpng2_info_callback() in readpng2.c, which
 * in turn is called by libpng after all of the pre-IDAT chunks have been
 * read and processed--i.e., we now have enough info to finish initializing */

static void rpng2_x_init()
{
    ulg i;
    ulg rowbytes = rpng2_info.rowbytes;

    Trace((stderr, "beginning rpng2_x_init()\n"))
    Trace((stderr, "  rowbytes = %ld\n", rpng2_info.rowbytes))
    Trace((stderr, "  width  = %ld\n", rpng2_info.width))
    Trace((stderr, "  height = %ld\n", rpng2_info.height))

    rpng2_info.image_data = (uch *)malloc(rowbytes * rpng2_info.height);
    if (!rpng2_info.image_data) {
        readpng2_cleanup(&rpng2_info);
        return;
    }

    rpng2_info.row_pointers = (uch **)malloc(rpng2_info.height * sizeof(uch *));
    if (!rpng2_info.row_pointers) {
        free(rpng2_info.image_data);
        rpng2_info.image_data = NULL;
        readpng2_cleanup(&rpng2_info);
        return;
    }

    for (i = 0;  i < rpng2_info.height;  ++i)
        rpng2_info.row_pointers[i] = rpng2_info.image_data + i*rowbytes;


    /* do the basic X initialization stuff, make the window, and fill it with
     * the user-specified, file-specified or default background color or
     * pattern */

    if (rpng2_x_create_window()) {
        readpng2_cleanup(&rpng2_info);
        return;
    }
}





static int rpng2_x_create_window()
{
    ulg bg_red   = rpng2_info.bg_red;
    ulg bg_green = rpng2_info.bg_green;
    ulg bg_blue  = rpng2_info.bg_blue;
    ulg bg_pixel = 0L;
    int screen, pad;
    uch *xdata;
    Window root;
    XEvent e;
    XGCValues gcvalues;
    XSetWindowAttributes attr;
    XSizeHints *size_hints;
    XTextProperty windowName, *pWindowName = &windowName;
    XTextProperty iconName, *pIconName = &iconName;
    XVisualInfo visual_info;
    XWMHints *wm_hints;


    Trace((stderr, "beginning rpng2_x_create_window()\n"))

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

/* GRR:  add 8-bit support */
    if (/* depth != 8 && */ depth != 16 && depth != 24 && depth != 32) {
        fprintf(stderr,
          "screen depth %d not supported (only 16-, 24- or 32-bit TrueColor)\n",
          depth);
        return 2;
    }

    XMatchVisualInfo(display, screen, depth,
      (depth == 8)? PseudoColor : TrueColor, &visual_info);
    visual = visual_info.visual;

    RedMask   = visual->red_mask;
    GreenMask = visual->green_mask;
    BlueMask  = visual->blue_mask;

/* GRR:  add/check 8-bit support */
    if (depth == 8) {
        colormap = XCreateColormap(display, root, visual, AllocNone);
        if (!colormap) {
            fprintf(stderr, "XCreateColormap() failed\n");
            return 2;
        }
        have_colormap = TRUE;
        bg_image = FALSE;	/* gradient just wastes palette entries */
    } else if (depth == 16) {
        RPixelShift = 15 - rpng2_x_msb(RedMask);   /* these are right-shifts */
        GPixelShift = 15 - rpng2_x_msb(GreenMask);
        BPixelShift = 15 - rpng2_x_msb(BlueMask);
    } else /* if (depth > 16) */ {
        RPixelShift = rpng2_x_msb(RedMask) - 7;    /* these are left-shifts */
        GPixelShift = rpng2_x_msb(GreenMask) - 7;
        BPixelShift = rpng2_x_msb(BlueMask) - 7;
    }

/*---------------------------------------------------------------------------
    Finally, create the window.
  ---------------------------------------------------------------------------*/

    attr.backing_store = Always;
    attr.event_mask = ExposureMask | KeyPressMask | ButtonPressMask;

    window = XCreateWindow(display, root, 0, 0, rpng2_info.width,
      rpng2_info.height, 0, depth, InputOutput, visual,
      CWBackingStore | CWEventMask, &attr);

    if (window == None) {
        fprintf(stderr, "XCreateWindow() failed\n");
        return 2;
    } else
        have_window = TRUE;

    if (depth == 8)
        XSetWindowColormap(display, window, colormap);

    if (!XStringListToTextProperty(&window_name, 1, pWindowName))
        pWindowName = NULL;
    if (!XStringListToTextProperty(&icon_name, 1, pIconName))
        pIconName = NULL;

    /* OK if either hints allocation fails; XSetWMProperties() allows NULLs */

    if ((size_hints = XAllocSizeHints()) != NULL) {
        /* window will not be resizable */
        size_hints->flags = PMinSize | PMaxSize;
        size_hints->min_width = size_hints->max_width = rpng2_info.width;
        size_hints->min_height = size_hints->max_height = rpng2_info.height;
    }

    if ((wm_hints = XAllocWMHints()) != NULL) {
        wm_hints->initial_state = NormalState;
        wm_hints->input = True;
     /* wm_hints->icon_pixmap = icon_pixmap; */
        wm_hints->flags = StateHint | InputHint  /* | IconPixmapHint */ ;
    }

    XSetWMProperties(display, window, pWindowName, pIconName, NULL, 0,
      size_hints, wm_hints, NULL);

    XMapWindow(display, window);

    gc = XCreateGC(display, window, 0, &gcvalues);

/*---------------------------------------------------------------------------
    Allocate memory for the X- and display-specific version of the image.
  ---------------------------------------------------------------------------*/

    if (depth == 24 || depth == 32) {
        xdata = (uch *)malloc(4*rpng2_info.width*rpng2_info.height);
        pad = 32;
    } else if (depth == 16) {
        xdata = (uch *)malloc(2*rpng2_info.width*rpng2_info.height);
        pad = 16;
    } else /* depth == 8 */ {
        xdata = (uch *)malloc(rpng2_info.width*rpng2_info.height);
        pad = 8;
    }

    if (!xdata) {
        fprintf(stderr, PROGNAME ":  unable to allocate image memory\n");
        return 4;
    }

    ximage = XCreateImage(display, visual, depth, ZPixmap, 0,
      (char *)xdata, rpng2_info.width, rpng2_info.height, pad, 0);

    if (!ximage) {
        fprintf(stderr, PROGNAME ":  XCreateImage() failed\n");
        free(xdata);
        return 3;
    }

    /* to avoid testing the bitmap order every pixel (or doubling the size of
     * the drawing routine with a giant if-test), we arbitrarily set the byte
     * order to MSBFirst and let Xlib worry about inverting things on little-
     * endian machines (e.g., Linux/x86, old VAXen, etc.)--this is not the
     * most efficient approach (the giant if-test would be better), but in
     * the interest of clarity, we'll take the easy way out... */

    ximage->byte_order = MSBFirst;

/*---------------------------------------------------------------------------
    Fill window with the specified background color (default is black) or
    faked "background image" (but latter is disabled if 8-bit; gradients
    just waste palette entries).
  ---------------------------------------------------------------------------*/

    if (bg_image)
        rpng2_x_load_bg_image();	/* resets bg_image if fails */

    if (!bg_image) {
        if (depth == 24 || depth == 32) {
            bg_pixel = (bg_red   << RPixelShift) |
                       (bg_green << GPixelShift) |
                       (bg_blue  << BPixelShift);
        } else if (depth == 16) {
            bg_pixel = (((bg_red   << 8) >> RPixelShift) & RedMask)   |
                       (((bg_green << 8) >> GPixelShift) & GreenMask) |
                       (((bg_blue  << 8) >> BPixelShift) & BlueMask);
        } else /* depth == 8 */ {

            /* GRR:  add 8-bit support */

        }
        XSetForeground(display, gc, bg_pixel);
        XFillRectangle(display, window, gc, 0, 0, rpng2_info.width,
          rpng2_info.height);
    }

/*---------------------------------------------------------------------------
    Wait for first Expose event to do any drawing, then flush and return.
  ---------------------------------------------------------------------------*/

    do
        XNextEvent(display, &e);
    while (e.type != Expose || e.xexpose.count);

    XFlush(display);

    return 0;

} /* end function rpng2_x_create_window() */





static int rpng2_x_load_bg_image()
{
    uch *src, *dest;
    uch r1, r2, g1, g2, b1, b2;
    uch r1_inv, r2_inv, g1_inv, g2_inv, b1_inv, b2_inv;
    int k, hmax, max;
    int xidx, yidx, yidx_max = (bgscale-1);
    int even_odd_vert, even_odd_horiz, even_odd;
    int invert_gradient2 = (bg[pat].type & 0x08);
    int invert_column;
    int ximage_rowbytes = ximage->bytes_per_line;
    ulg i, row;
    ulg pixel;

/*---------------------------------------------------------------------------
    Allocate buffer for fake background image to be used with transparent
    images; if this fails, revert to plain background color.
  ---------------------------------------------------------------------------*/

    bg_rowbytes = 3 * rpng2_info.width;
    bg_data = (uch *)malloc(bg_rowbytes * rpng2_info.height);
    if (!bg_data) {
        fprintf(stderr, PROGNAME
          ":  unable to allocate memory for background image\n");
        bg_image = 0;
        return 1;
    }

/*---------------------------------------------------------------------------
    Vertical gradients (ramps) in NxN squares, alternating direction and
    colors (N == bgscale).
  ---------------------------------------------------------------------------*/

    if ((bg[pat].type & 0x07) == 0) {
        uch r1_min  = rgb[bg[pat].rgb1_min].r;
        uch g1_min  = rgb[bg[pat].rgb1_min].g;
        uch b1_min  = rgb[bg[pat].rgb1_min].b;
        uch r2_min  = rgb[bg[pat].rgb2_min].r;
        uch g2_min  = rgb[bg[pat].rgb2_min].g;
        uch b2_min  = rgb[bg[pat].rgb2_min].b;
        int r1_diff = rgb[bg[pat].rgb1_max].r - r1_min;
        int g1_diff = rgb[bg[pat].rgb1_max].g - g1_min;
        int b1_diff = rgb[bg[pat].rgb1_max].b - b1_min;
        int r2_diff = rgb[bg[pat].rgb2_max].r - r2_min;
        int g2_diff = rgb[bg[pat].rgb2_max].g - g2_min;
        int b2_diff = rgb[bg[pat].rgb2_max].b - b2_min;

        for (row = 0;  row < rpng2_info.height;  ++row) {
            yidx = row % bgscale;
            even_odd_vert = (row / bgscale) & 1;

            r1 = r1_min + (r1_diff * yidx) / yidx_max;
            g1 = g1_min + (g1_diff * yidx) / yidx_max;
            b1 = b1_min + (b1_diff * yidx) / yidx_max;
            r1_inv = r1_min + (r1_diff * (yidx_max-yidx)) / yidx_max;
            g1_inv = g1_min + (g1_diff * (yidx_max-yidx)) / yidx_max;
            b1_inv = b1_min + (b1_diff * (yidx_max-yidx)) / yidx_max;

            r2 = r2_min + (r2_diff * yidx) / yidx_max;
            g2 = g2_min + (g2_diff * yidx) / yidx_max;
            b2 = b2_min + (b2_diff * yidx) / yidx_max;
            r2_inv = r2_min + (r2_diff * (yidx_max-yidx)) / yidx_max;
            g2_inv = g2_min + (g2_diff * (yidx_max-yidx)) / yidx_max;
            b2_inv = b2_min + (b2_diff * (yidx_max-yidx)) / yidx_max;

            dest = bg_data + row*bg_rowbytes;
            for (i = 0;  i < rpng2_info.width;  ++i) {
                even_odd_horiz = (i / bgscale) & 1;
                even_odd = even_odd_vert ^ even_odd_horiz;
                invert_column =
                  (even_odd_horiz && (bg[pat].type & 0x10));
                if (even_odd == 0) {		/* gradient #1 */
                    if (invert_column) {
                        *dest++ = r1_inv;
                        *dest++ = g1_inv;
                        *dest++ = b1_inv;
                    } else {
                        *dest++ = r1;
                        *dest++ = g1;
                        *dest++ = b1;
                    }
                } else {			/* gradient #2 */
                    if ((invert_column && invert_gradient2) ||
                        (!invert_column && !invert_gradient2))
                    {
                        *dest++ = r2;      /* not inverted or */
                        *dest++ = g2;      /*  doubly inverted */
                        *dest++ = b2;
                    } else {
                        *dest++ = r2_inv;
                        *dest++ = g2_inv;  /* singly inverted */
                        *dest++ = b2_inv;
                    }
                }
            }
        }

/*---------------------------------------------------------------------------
    Soft gradient-diamonds with scale = bgscale.  Code contributed by Adam
    M. Costello.
  ---------------------------------------------------------------------------*/

    } else if ((bg[pat].type & 0x07) == 1) {

        hmax = (bgscale-1)/2;	/* half the max weight of a color */
        max = 2*hmax;		/* the max weight of a color */