io-svg.c

   1 #include <stdio.h> /* fprintf, printf */
   2 #include <string.h> /* memcpy */
   3
   4 #include <cairo.h>
   5 #include <gdk/gdk.h>
   6 #include <gdk-pixbuf/gdk-pixbuf.h> /* includes glib.h */
   7 #include <svgtiny.h>
   8
   9 /*
  10  * The width and height of the viewport that we'll render the SVG
  11  * into. The final "picture" may not actually be this size; based on
  12  * the height, width, viewBox, and preserveAspectRatio attributes in
  13  * the SVG itself, libsvgtiny may scale, stretch, offset, etc. the
  14  * paths to make them fit nicely into the viewport.
  15  */
  16 #define VIEWPORT_WIDTH 512
  17 #define VIEWPORT_HEIGHT 512
  18
  19 /* Convenient typedefs for libsvgtiny */
  20 typedef struct svgtiny_diagram diagram_t;
  21 typedef struct svgtiny_shape shape_t;
  22
  23
  24 typedef struct {
  25   GdkPixbufModuleUpdatedFunc  updated_func;
  26   GdkPixbufModulePreparedFunc prepared_func;
  27   GdkPixbufModuleSizeFunc     size_func;
  28   gpointer                    user_data;
  29
  30   /* The SVG "file" that we're building in memory. */
  31   char*                       svg_data;
  32
  33   /* How far into svg_data are we? This should always point to the
  34      next empty byte. If (for example) svg_data_size is 2, then
  35      svg_data[0] and svg_data[1] are used, but svg_data[2] is free. */
  36   size_t svg_data_size;
  37
  38 } SvgTinyContext;
  39
  40
  41 /**
  42  * @brief Render an svgtiny path using cairo.
  43  *
  44  * @param cr
  45  *   A pointer to a valid cairo context.
  46  *
  47  * @param path
  48  *   A pointer to an svgtiny shape that will be rendered on the
  49  *   cairo context's target surface.
  50  */
  51 static void render_path(cairo_t* cr, shape_t* path) {
  52   unsigned int j;
  53
  54   cairo_new_path(cr);
  55   for (j = 0; j != path->path_length; ) {
  56     switch ((int) path->path[j]) {
  57     case svgtiny_PATH_MOVE:
  58       cairo_move_to(cr,
  59                     path->path[j + 1],
  60                     path->path[j + 2]);
  61       j += 3;
  62       break;
  63     case svgtiny_PATH_CLOSE:
  64       cairo_close_path(cr);
  65       j += 1;
  66       break;
  67     case svgtiny_PATH_LINE:
  68       cairo_line_to(cr,
  69                     path->path[j + 1],
  70                     path->path[j + 2]);
  71       j += 3;
  72       break;
  73     case svgtiny_PATH_BEZIER:
  74       cairo_curve_to(cr,
  75                      path->path[j + 1],
  76                      path->path[j + 2],
  77                      path->path[j + 3],
  78                      path->path[j + 4],
  79                      path->path[j + 5],
  80                      path->path[j + 6]);
  81       j += 7;
  82     }
  83   }
  84   if (path->fill != svgtiny_TRANSPARENT) {
  85     cairo_set_source_rgba(cr,
  86                           svgtiny_RED(path->fill) / 255.0,
  87                           svgtiny_GREEN(path->fill) / 255.0,
  88                           svgtiny_BLUE(path->fill) / 255.0,
  89                           1);
  90     cairo_fill_preserve(cr);
  91   }
  92   if (path->stroke != svgtiny_TRANSPARENT) {
  93     cairo_set_source_rgba(cr,
  94                           svgtiny_RED(path->stroke) / 255.0,
  95                           svgtiny_GREEN(path->stroke) / 255.0,
  96                           svgtiny_BLUE(path->stroke) / 255.0,
  97                           1);
  98     cairo_set_line_width(cr, path->stroke_width);
  99     cairo_stroke_preserve(cr);
 100   }
 101 }
 102
 103 /**
 104  * @brief Parse a buffer of SVG data into a diagram_t structure.
 105  *
 106  * @param buffer
 107  *   The buffer containing the SVG document.
 108  *
 109  * @param bytecount
 110  *   The number of bytes in @c buffer.
 111  *
 112  * @return If successful, a pointer to a @c diagram_t structure is
 113  *   returned; if not, @c NULL is returned. You are expected to @c
 114  *   svgtiny_free the result if it is valid.
 115  */
 116 static diagram_t* svgtiny_diagram_from_buffer(char* buffer,
 117                                               size_t bytecount,
 118                                               int width,
 119                                               int height,
 120                                               GError** error) {
 121   diagram_t* diagram;
 122   svgtiny_code code;
 123
 124   diagram = svgtiny_create();
 125   if (!diagram) {
 126     g_set_error_literal(error,
 127                         G_FILE_ERROR,
 128                         G_FILE_ERROR_NOMEM,
 129                         "out of memory in svgtiny_create()");
 130     return NULL;
 131   }
 132
 133   code = svgtiny_parse(diagram, buffer, bytecount, "", width, height);
 134
 135   if (code != svgtiny_OK) {
 136     switch (code) {
 137     case svgtiny_OUT_OF_MEMORY:
 138       g_set_error_literal(error,
 139                           G_FILE_ERROR,
 140                           G_FILE_ERROR_NOMEM,
 141                           "out of memory in svgtiny_parse()");
 142       break;
 143     case svgtiny_LIBDOM_ERROR:
 144       g_set_error_literal(error,
 145                           GDK_PIXBUF_ERROR,
 146                           GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
 147                           "invalid XML DOM in svgtiny_parse()");
 148       break;
 149     case svgtiny_NOT_SVG:
 150       g_set_error_literal(error,
 151                           GDK_PIXBUF_ERROR,
 152                           GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
 153                           "missing <svg> element in svgtiny_parse()");
 154       break;
 155     case svgtiny_SVG_ERROR:
 156       g_set_error(error,
 157                   GDK_PIXBUF_ERROR,
 158                   GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
 159                   "SVG format error in svgtiny_parse() on line %i: %s",
 160                   diagram->error_line,
 161                   diagram->error_message);
 162       break;
 163     }
 164     return NULL;
 165   }
 166
 167   return diagram;
 168 }
 169
 170 /**
 171  * @brief Create a cairo context from a libsvgtiny diagram.
 172  *
 173  * @param diagram
 174  *   A pointer to a valid libsvgtiny diagram.
 175  *
 176  * @return If successful, a pointer to a @c cairo_t context structure
 177  *   is returned; if not, @c NULL is returned. You are expected to @c
 178  *   cairo_destroy the result if it is valid.
 179  */
 180 static cairo_t* cairo_context_from_diagram(diagram_t* diagram) {
 181   cairo_t* cr;
 182   cairo_surface_t* surface;
 183   cairo_status_t crs;
 184   unsigned int i;
 185
 186   surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,
 187                                        diagram->width,
 188                                        diagram->height);
 189
 190   crs = cairo_surface_status(surface);
 191   if (crs != CAIRO_STATUS_SUCCESS) {
 192     fprintf(stderr,
 193             "cairo_image_surface_create failed: %s\n",
 194             cairo_status_to_string(crs));
 195     cairo_surface_destroy(surface);
 196     return NULL;
 197   }
 198
 199   cr = cairo_create(surface);
 200   crs = cairo_status(cr);
 201
 202   /* Immediately destroy the surface which is now accessible as
 203      cr->target */
 204   cairo_surface_destroy(surface);
 205
 206   if (crs != CAIRO_STATUS_SUCCESS) {
 207     fprintf(stderr,
 208             "cairo_create failed: %s\n",
 209             cairo_status_to_string(crs));
 210     cairo_destroy(cr);
 211     return NULL;
 212   }
 213
 214   cairo_set_source_rgba(cr, 0, 0, 0, 0);
 215   cairo_paint(cr);
 216
 217   /* Loop through the shapes in the diagram... */
 218   for (i = 0; i != diagram->shape_count; i++) {
 219
 220     /* If this shape is a path, just render it. */
 221     if (diagram->shape[i].path) {
 222       render_path(cr, &diagram->shape[i]);
 223     }
 224
 225     /* If this shape is text... */
 226     if (diagram->shape[i].text) {
 227       /* Figure out what color to use from the R/G/B components of the
 228          shape's stroke. */
 229       cairo_set_source_rgba(cr,
 230                             svgtiny_RED(diagram->shape[i].stroke) / 255.0,
 231                             svgtiny_GREEN(diagram->shape[i].stroke) / 255.0,
 232                             svgtiny_BLUE(diagram->shape[i].stroke) / 255.0,
 233                             1);
 234       /* Then move to the actual position of the text within the
 235          shape... */
 236       cairo_move_to(cr,
 237                     diagram->shape[i].text_x,
 238                     diagram->shape[i].text_y);
 239
 240       /* and draw it. */
 241       cairo_show_text(cr, diagram->shape[i].text);
 242     }
 243   }
 244
 245
 246   /* Check the status again just for good measure? */
 247   crs = cairo_status(cr);
 248   if (crs != CAIRO_STATUS_SUCCESS) {
 249     fprintf(stderr,
 250             "cairo error: %s\n",
 251             cairo_status_to_string(crs));
 252     cairo_destroy(cr);
 253     return NULL;
 254   }
 255
 256   return cr;
 257 }
 258
 259 /**
 260  * @brief Create a GdkPixbuf from a buffer of SVG data.
 261  *
 262  * @param buffer
 263  *   The buffer containing the SVG document.
 264  *
 265  * @param bytecount
 266  *   The number of bytes in @c buffer.
 267  *
 268  * @param error
 269  *   The address of a @c GError pointer that we use to return errors.
 270  *
 271  * @return If successful, a valid pointer to a @c GdkPixbuf is
 272  *   returned; if not, @c NULL is returned and @c error is populated.
 273  */
 274 static GdkPixbuf* gdk_pixbuf_from_svg_buffer(char* buffer,
 275                                              size_t bytecount,
 276                                              GError** error) {
 277   diagram_t* diagram;
 278   cairo_t* cr = 0;
 279   GdkPixbuf* pb;
 280   GError* sub_error = NULL;
 281
 282   diagram = svgtiny_diagram_from_buffer(buffer,
 283                                         bytecount,
 284                                         VIEWPORT_WIDTH,
 285                                         VIEWPORT_HEIGHT,
 286                                         &sub_error);
 287   if (!diagram) {
 288     g_propagate_error(error, sub_error);
 289     return NULL;
 290   }
 291
 292   cr = cairo_context_from_diagram(diagram);
 293   if (!cr) {
 294     svgtiny_free(diagram);
 295     g_set_error_literal(error,
 296                         GDK_PIXBUF_ERROR,
 297                         GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
 298                         "could not create Cairo surface from SVG diagram");
 299     return NULL;
 300   }
 301
 302
 303   /* I've gone back and forth on this about five times: we use the
 304    * diagram width and height, and not the viewport width and height.
 305    * This can ultimately render an image that's larger than the
 306    * viewport size, but I think GDK will resize the final pixbuf
 307    * anyway. More importantly, rendering small icons at a larger
 308    * (viewport) size seems to make the whole thing go ape-shit.
 309    * So for now I'm back in the diagram camp.
 310    */
 311   pb = gdk_pixbuf_get_from_surface(cairo_get_target(cr),
 312                                    0,
 313                                    0,
 314                                    diagram->width,
 315                                    diagram->height);
 316
 317
 318   if (!pb) {
 319     g_set_error_literal(error,
 320                         GDK_PIXBUF_ERROR,
 321                         GDK_PIXBUF_ERROR_FAILED,
 322                         "failed to obtain a GdkPixbuf from Cairo surface");
 323   }
 324
 325   return pb;
 326 }
 327
 328
 329 static gpointer gdk_pixbuf_begin_load(GdkPixbufModuleSizeFunc size_func,
 330                                       GdkPixbufModulePreparedFunc prep_func,
 331                                       GdkPixbufModuleUpdatedFunc updated_func,
 332                                       gpointer user_data,
 333                                       GError **error) {
 334
 335   SvgTinyContext* context = g_new(SvgTinyContext, 1);
 336
 337   context->size_func      = size_func;
 338   context->prepared_func  = prep_func;
 339   context->updated_func   = updated_func;
 340   context->user_data      = user_data;
 341
 342   context->svg_data       = NULL;
 343   context->svg_data_size  = 0;
 344
 345   return context;
 346 }
 347
 348 static gboolean gdk_pixbuf_load_increment(gpointer data,
 349                                           const guchar* buf,
 350                                           guint buf_size,
 351                                           GError** error) {
 352   size_t increment = 0;
 353   SvgTinyContext* context = (SvgTinyContext*)data;
 354
 355   /* YOLO, no error checking */
 356   context->svg_data = g_realloc(context->svg_data,
 357                                 context->svg_data_size + buf_size);
 358   memcpy(context->svg_data + context->svg_data_size, buf, buf_size);
 359   context->svg_data_size += buf_size;
 360
 361   return TRUE;
 362 }
 363
 364 static void emit_updated(SvgTinyContext* context, GdkPixbuf* pixbuf) {
 365   if (context->updated_func != NULL) {
 366     (*context->updated_func)(pixbuf,
 367                              0,
 368                              0,
 369                              gdk_pixbuf_get_width(pixbuf),
 370                              gdk_pixbuf_get_height(pixbuf),
 371                              context->user_data);
 372   }
 373 }
 374
 375 static void emit_prepared(SvgTinyContext* context, GdkPixbuf* pixbuf) {
 376   if (context->prepared_func != NULL) {
 377     (*context->prepared_func)(pixbuf, NULL, context->user_data);
 378   }
 379 }
 380
 381
 382 static gboolean gdk_pixbuf_stop_load(gpointer data, GError **error) {
 383   SvgTinyContext* context = (SvgTinyContext*)data;
 384   GdkPixbuf* pixbuf = NULL;
 385   gboolean result = TRUE;
 386   GError* sub_error = NULL;
 387
 388   pixbuf = gdk_pixbuf_from_svg_buffer(context->svg_data,
 389                                       context->svg_data_size,
 390                                       &sub_error);
 391
 392   if (pixbuf != NULL) {
 393     emit_prepared(context, pixbuf);
 394     emit_updated(context, pixbuf);
 395     g_object_unref(pixbuf);
 396   }
 397   else {
 398     g_propagate_error(error, sub_error);
 399     result = FALSE;
 400   }
 401   g_free(context->svg_data);
 402   g_free(context);
 403
 404   return result;
 405 }
 406
 407
 408 G_MODULE_EXPORT void fill_vtable(GdkPixbufModule* module);
 409 void fill_vtable(GdkPixbufModule* module) {
 410   module->begin_load = gdk_pixbuf_begin_load;
 411   module->load_increment = gdk_pixbuf_load_increment;
 412   module->stop_load = gdk_pixbuf_stop_load;
 413 }
 414
 415 G_MODULE_EXPORT void fill_info(GdkPixbufFormat *info);
 416 void fill_info(GdkPixbufFormat* info) {
 417   /* Borrowed from librsvg-2.40.21 */
 418   static const GdkPixbufModulePattern signature[] = {
 419     {  " <svg",  "*    ", 100 },
 420     {  " <!DOCTYPE svg",  "*             ", 100 },
 421     { NULL, NULL, 0 }
 422   };
 423
 424   /* I'm not sure if we should support gzipped svg here? */
 425   static const gchar *mime_types[] = {
 426     "image/svg+xml",
 427     "image/svg",
 428     "image/svg-xml",
 429     "image/vnd.adobe.svg+xml",
 430     "text/xml-svg",
 431     "image/svg+xml-compressed",
 432     NULL
 433   };
 434
 435   static const gchar *extensions[] = {
 436     "svg",
 437     "svgz",
 438     "svg.gz",
 439     NULL
 440   };
 441
 442   info->name        = "svg";
 443   info->signature   = (GdkPixbufModulePattern*)signature;
 444   info->description = "Scalable Vector Graphics";
 445   info->mime_types  = (gchar**)mime_types;
 446   info->extensions  = (gchar**)extensions;
 447   info->flags       = GDK_PIXBUF_FORMAT_SCALABLE;
 448   info->license     = "AGPL3";
 449 }
 450
 451
 452 int main(int argc, char** argv) {
 453   char* svgpath;
 454   char* pngpath;
 455   FILE* fp;
 456   GError* err = NULL;
 457   GdkPixbuf* pb;
 458
 459   /* Parse arguments, and maybe print usage */
 460   if (argc < 3) {
 461     printf("Usage: %s INPUT OUTPUT\n", argv[0]);
 462     printf("Convert an SVG file (INPUT) to a PNG file (OUTPUT)\n");
 463     return 2;
 464   }
 465
 466   svgpath = argv[1];
 467   pngpath = argv[2];
 468
 469   pb = gdk_pixbuf_new_from_file(svgpath, &err);
 470   if (!pb) {
 471     fprintf(stderr,
 472             "Error %d in gdk_pixbuf_new_from_file: %s\n",
 473             err->code,
 474             err->message);
 475     g_error_free(err);
 476     return 1;
 477   }
 478
 479   gdk_pixbuf_save(pb, pngpath, "png", NULL, NULL);
 480   g_object_unref(pb);
 481   return 0;
 482 }