app/export_png.c

   1 /* Dia -- a diagram creation/manipulation program
   2  * Copyright (C) 1998 Alexander Larsson
   3  *
   4  * export_png.c: export a diagram to a PNG file.
   5  * Copyright (C) 2000 James Henstridge
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  20  */
  21
  22 #include <config.h>
  23
  24 #if defined(HAVE_LIBPNG) && defined(HAVE_LIBART)
  25
  26 #include <stdio.h>
  27 #include <png.h>
  28
  29 #include "intl.h"
  30 #include "filter.h"
  31 #include "render_libart.h"
  32 #include "display.h"
  33 #include "message.h"
  34
  35 /* the dots per centimetre to render this diagram at */
  36 /* this matches the setting `100%' setting in dia. */
  37 #define DPCM 20
  38
  39 /* the height of the band to use when rendering.  Smaller bands mean
  40  * rendering is slower, but less memory is used.  Setting this to G_MAXINT
  41  * should get the renderer to use one pass. */
  42 #define BAND_HEIGHT 50
  43
  44 static void
  45 export_png(DiagramData *data, const gchar *filename,
  46            const gchar *diafilename, void* user_data)
  47 {
  48   Rectangle *ext = &data->extents;
  49   DDisplay *ddisp;
  50   RendererLibart *renderer;
  51   guint32 width, height, band, row, i;
  52   real band_height;
  53
  54   FILE *fp;
  55   png_structp png;
  56   png_infop info;
  57   png_color_8 sig_bit;
  58   png_bytep *row_ptr;
  59
  60   width  = (guint32) ((ext->right - ext->left) * DPCM * data->paper.scaling);
  61   height = (guint32) ((ext->bottom - ext->top) * DPCM * data->paper.scaling);
  62
  63   /* we render in bands to try to keep memory consumption down ... */
  64   band = MIN(height, BAND_HEIGHT);
  65   band_height = (real)band / (DPCM * data->paper.scaling);
  66
  67   /* create a fake ddisp to keep the renderer happy */
  68   ddisp = g_new0(DDisplay, 1);
  69   ddisp->zoom_factor = DPCM * data->paper.scaling;
  70   ddisp->visible = *ext;
  71   ddisp->visible.bottom = MIN(ddisp->visible.bottom,
  72                               ddisp->visible.top + band_height);
  73   renderer = new_libart_renderer(ddisp, 0);
  74   libart_renderer_set_size(renderer, NULL, width, band);
  75   ddisp->renderer = (Renderer *)renderer;
  76
  77   fp = fopen(filename, "wb");
  78   if (fp == NULL) {
  79     message_error(_("Couldn't open: '%s' for writing.\n"), filename);
  80     goto error;
  81   }
  82
  83   png = png_create_write_struct(PNG_LIBPNG_VER_STRING,
  84                                 NULL, NULL, NULL);
  85   if (!png) {
  86     fclose(fp);
  87     message_error(_("Could not create PNG write structure"));
  88     goto error;
  89   }
  90
  91   /* allocate/initialise the image information data */
  92   info = png_create_info_struct(png);
  93   if (!info) {
  94     fclose(fp);
  95     png_destroy_write_struct(&png, (png_infopp)NULL);
  96     message_error(_("Could not create PNG header info structure"));
  97     goto error;
  98   }
  99
 100   /* set error handling ... */
 101   if (setjmp(png->jmpbuf)) {
 102     fclose(fp);
 103     png_destroy_write_struct(&png, (png_infopp)NULL);
 104     message_error(_("Error occurred while writing PNG"));
 105     goto error;
 106   }
 107   /* the compiler said band may be clobbered by setjmp, so we set it again
 108    * here. */
 109   band = MIN(height, BAND_HEIGHT);
 110
 111   png_init_io(png, fp);
 112
 113   /* header fields */
 114   png_set_IHDR(png, info, width, height, 8,
 115                PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE,
 116                PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 117   sig_bit.red = 8;
 118   sig_bit.green = 8;
 119   sig_bit.blue = 8;
 120   png_set_sBIT(png, info, &sig_bit);
 121
 122   png_write_info(png, info);
 123   png_set_shift(png, &sig_bit);
 124   png_set_packing(png);
 125
 126   row_ptr = g_new(png_bytep, band);
 127
 128   for (row = 0; row < height; row += band) {
 129     /* render band */
 130     for (i = 0; i < width*band; i++) {
 131       renderer->rgb_buffer[3*i]   = 0xff * data->bg_color.red;
 132       renderer->rgb_buffer[3*i+1] = 0xff * data->bg_color.green;
 133       renderer->rgb_buffer[3*i+2] = 0xff * data->bg_color.blue;
 134     }
 135     data_render(data, (Renderer *)renderer, &ddisp->visible, NULL,NULL);
 136     /* write rows to png file */
 137     for (i = 0; i < band; i++)
 138       row_ptr[i] = renderer->rgb_buffer + 3 * i * width;
 139     png_write_rows(png, row_ptr, MIN(band, height - row));
 140
 141     ddisp->visible.top    += band_height;
 142     ddisp->visible.bottom += band_height;
 143   }
 144   g_free(row_ptr);
 145   png_write_end(png, info);
 146   png_destroy_write_struct(&png, (png_infopp)NULL);
 147   fclose(fp);
 148
 149  error:
 150   destroy_libart_renderer(renderer);
 151   g_free(ddisp);
 152   return;
 153 }
 154
 155 static const gchar *extensions[] = { "png", NULL };
 156 DiaExportFilter png_export_filter = {
 157   N_("Portable Network Graphics"),
 158   extensions,
 159   export_png
 160 };
 161
 162 #endif