modules/codec/libass.c

   1 /*****************************************************************************
   2  * SSA/ASS subtitle decoder using libass.
   3  *****************************************************************************
   4  * Copyright (C) 2008-2009 the VideoLAN team
   5  * $Id$
   6  *
   7  * Authors: Laurent Aimar <fenrir@videolan.org>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 /*****************************************************************************
  25  * Preamble
  26  *****************************************************************************/
  27
  28 #ifdef HAVE_CONFIG_H
  29 #   include "config.h"
  30 #endif
  31
  32 #include <string.h>
  33 #include <limits.h>
  34 #include <assert.h>
  35 #include <math.h>
  36
  37 #include <vlc_common.h>
  38 #include <vlc_plugin.h>
  39 #include <vlc_codec.h>
  40 #include <vlc_input.h>
  41 #include <vlc_dialog.h>
  42
  43 #include <ass/ass.h>
  44
  45 #if defined(WIN32)
  46 #   include <vlc_charset.h>
  47 #endif
  48
  49 /*****************************************************************************
  50  * Module descriptor
  51  *****************************************************************************/
  52 static int  Create ( vlc_object_t * );
  53 static void Destroy( vlc_object_t * );
  54
  55 vlc_module_begin ()
  56     set_shortname( N_("Subtitles (advanced)"))
  57     set_description( N_("Subtitle renderers using libass") )
  58     set_capability( "decoder", 100 )
  59     set_category( CAT_INPUT )
  60     set_subcategory( SUBCAT_INPUT_SCODEC )
  61     set_callbacks( Create, Destroy )
  62 vlc_module_end ()
  63
  64 /*****************************************************************************
  65  * Local prototypes
  66  *****************************************************************************/
  67 static subpicture_t *DecodeBlock( decoder_t *, block_t ** );
  68
  69 /* */
  70 struct decoder_sys_t
  71 {
  72     mtime_t        i_max_stop;
  73
  74     /* The following fields of decoder_sys_t are shared between decoder and spu units */
  75     vlc_mutex_t    lock;
  76     int            i_refcount;
  77
  78     /* */
  79     ASS_Library    *p_library;
  80     ASS_Renderer   *p_renderer;
  81     video_format_t fmt;
  82
  83     /* */
  84     ASS_Track      *p_track;
  85 };
  86 static void DecSysRelease( decoder_sys_t *p_sys );
  87 static void DecSysHold( decoder_sys_t *p_sys );
  88
  89 /* */
  90 static int SubpictureValidate( subpicture_t *,
  91                                bool, const video_format_t *,
  92                                bool, const video_format_t *,
  93                                mtime_t );
  94 static void SubpictureUpdate( subpicture_t *,
  95                               const video_format_t *,
  96                               const video_format_t *,
  97                               mtime_t );
  98 static void SubpictureDestroy( subpicture_t * );
  99
 100 struct subpicture_updater_sys_t
 101 {
 102     decoder_sys_t *p_dec_sys;
 103     void          *p_subs_data;
 104     int           i_subs_len;
 105     mtime_t       i_pts;
 106
 107     ASS_Image     *p_img;
 108 };
 109
 110 typedef struct
 111 {
 112     int x0;
 113     int y0;
 114     int x1;
 115     int y1;
 116 } rectangle_t;
 117
 118 static int BuildRegions( rectangle_t *p_region, int i_max_region, ASS_Image *p_img_list, int i_width, int i_height );
 119 static void RegionDraw( subpicture_region_t *p_region, ASS_Image *p_img );
 120
 121 //#define DEBUG_REGION
 122
 123 /*****************************************************************************
 124  * Create: Open libass decoder.
 125  *****************************************************************************/
 126 static int Create( vlc_object_t *p_this )
 127 {
 128     decoder_t *p_dec = (decoder_t *)p_this;
 129     decoder_sys_t *p_sys;
 130
 131     if( p_dec->fmt_in.i_codec != VLC_CODEC_SSA )
 132         return VLC_EGENERIC;
 133
 134     p_dec->pf_decode_sub = DecodeBlock;
 135
 136     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 137     if( !p_sys )
 138         return VLC_ENOMEM;
 139
 140     /* */
 141     vlc_mutex_init( &p_sys->lock );
 142     p_sys->i_refcount = 1;
 143     memset( &p_sys->fmt, 0, sizeof(p_sys->fmt) );
 144     p_sys->i_max_stop = VLC_TS_INVALID;
 145     p_sys->p_library  = NULL;
 146     p_sys->p_renderer = NULL;
 147     p_sys->p_track    = NULL;
 148
 149     /* Create libass library */
 150     ASS_Library *p_library = p_sys->p_library = ass_library_init();
 151     if( !p_library )
 152     {
 153         msg_Warn( p_dec, "Libass library creation failed" );
 154         DecSysRelease( p_sys );
 155         return VLC_EGENERIC;
 156     }
 157
 158     /* load attachments */
 159     input_attachment_t  **pp_attachments;
 160     int                   i_attachments;
 161     if( decoder_GetInputAttachments( p_dec, &pp_attachments, &i_attachments ))
 162     {
 163         i_attachments = 0;
 164         pp_attachments = NULL;
 165     }
 166     for( int k = 0; k < i_attachments; k++ )
 167     {
 168         input_attachment_t *p_attach = pp_attachments[k];
 169
 170         if( !strcasecmp( p_attach->psz_mime, "application/x-truetype-font" ) )
 171         {
 172             msg_Dbg( p_dec, "adding embedded font %s", p_attach->psz_name );
 173
 174             ass_add_font( p_sys->p_library, p_attach->psz_name, p_attach->p_data, p_attach->i_data );
 175         }
 176         vlc_input_attachment_Delete( p_attach );
 177     }
 178     free( pp_attachments );
 179
 180     ass_set_extract_fonts( p_library, true );
 181     ass_set_style_overrides( p_library, NULL );
 182
 183     /* Create the renderer */
 184     ASS_Renderer *p_renderer = p_sys->p_renderer = ass_renderer_init( p_library );
 185     if( !p_renderer )
 186     {
 187         msg_Warn( p_dec, "Libass renderer creation failed" );
 188         DecSysRelease( p_sys );
 189         return VLC_EGENERIC;
 190     }
 191
 192     ass_set_use_margins( p_renderer, false);
 193     //if( false )
 194     //    ass_set_margins( p_renderer, int t, int b, int l, int r);
 195     ass_set_hinting( p_renderer, ASS_HINTING_LIGHT );
 196     ass_set_font_scale( p_renderer, 1.0 );
 197     ass_set_line_spacing( p_renderer, 0.0 );
 198
 199     const char *psz_font = NULL; /* We don't ship a default font with VLC */
 200     const char *psz_family = "Arial"; /* Use Arial if we can't find anything more suitable */
 201
 202 #ifdef HAVE_FONTCONFIG
 203 #if defined(WIN32)
 204     dialog_progress_bar_t *p_dialog =
 205         dialog_ProgressCreate( p_dec,
 206                                _("Building font cache"),
 207                                _( "Please wait while your font cache is rebuilt.\n"
 208                                   "This should take less than a minute." ), NULL );
 209     if( p_dialog )
 210         dialog_ProgressSet( p_dialog, NULL, 0.2 );
 211 #endif
 212     ass_set_fonts( p_renderer, psz_font, psz_family, true, NULL, 1 );  // setup default font/family
 213 #ifdef WIN32
 214     if( p_dialog )
 215     {
 216         dialog_ProgressSet( p_dialog, NULL, 1.0 );
 217         dialog_ProgressDestroy( p_dialog );
 218     }
 219 #endif
 220 #else
 221     /* FIXME you HAVE to give him a font if no fontconfig */
 222     ass_set_fonts( p_renderer, psz_font, psz_family, false, NULL, 1 );
 223 #endif
 224
 225     /* Add a track */
 226     ASS_Track *p_track = p_sys->p_track = ass_new_track( p_sys->p_library );
 227     if( !p_track )
 228     {
 229         DecSysRelease( p_sys );
 230         return VLC_EGENERIC;
 231     }
 232     ass_process_codec_private( p_track, p_dec->fmt_in.p_extra, p_dec->fmt_in.i_extra );
 233
 234     p_dec->fmt_out.i_cat = SPU_ES;
 235     p_dec->fmt_out.i_codec = VLC_CODEC_RGBA;
 236
 237     return VLC_SUCCESS;
 238 }
 239
 240 /*****************************************************************************
 241  * Destroy: finish
 242  *****************************************************************************/
 243 static void Destroy( vlc_object_t *p_this )
 244 {
 245     decoder_t *p_dec = (decoder_t *)p_this;
 246
 247     DecSysRelease( p_dec->p_sys );
 248 }
 249
 250 static void DecSysHold( decoder_sys_t *p_sys )
 251 {
 252     vlc_mutex_lock( &p_sys->lock );
 253     p_sys->i_refcount++;
 254     vlc_mutex_unlock( &p_sys->lock );
 255 }
 256 static void DecSysRelease( decoder_sys_t *p_sys )
 257 {
 258     /* */
 259     vlc_mutex_lock( &p_sys->lock );
 260     p_sys->i_refcount--;
 261     if( p_sys->i_refcount > 0 )
 262     {
 263         vlc_mutex_unlock( &p_sys->lock );
 264         return;
 265     }
 266     vlc_mutex_unlock( &p_sys->lock );
 267     vlc_mutex_destroy( &p_sys->lock );
 268
 269     if( p_sys->p_track )
 270         ass_free_track( p_sys->p_track );
 271     if( p_sys->p_renderer )
 272         ass_renderer_done( p_sys->p_renderer );
 273     if( p_sys->p_library )
 274         ass_library_done( p_sys->p_library );
 275
 276     free( p_sys );
 277 }
 278
 279 /****************************************************************************
 280  * DecodeBlock:
 281  ****************************************************************************/
 282 static subpicture_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 283 {
 284     decoder_sys_t *p_sys = p_dec->p_sys;
 285
 286     subpicture_t *p_spu = NULL;
 287     block_t *p_block;
 288
 289     if( !pp_block || *pp_block == NULL )
 290         return NULL;
 291
 292     p_block = *pp_block;
 293     if( p_block->i_flags & (BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 294     {
 295         p_sys->i_max_stop = VLC_TS_INVALID;
 296         block_Release( p_block );
 297         return NULL;
 298     }
 299     *pp_block = NULL;
 300
 301     if( p_block->i_buffer == 0 || p_block->p_buffer[0] == '\0' )
 302     {
 303         block_Release( p_block );
 304         return NULL;
 305     }
 306
 307     subpicture_updater_sys_t *p_spu_sys = malloc( sizeof(*p_spu_sys) );
 308     if( !p_spu_sys )
 309     {
 310         block_Release( p_block );
 311         return NULL;
 312     }
 313
 314     subpicture_updater_t updater = {
 315         .pf_validate = SubpictureValidate,
 316         .pf_update   = SubpictureUpdate,
 317         .pf_destroy  = SubpictureDestroy,
 318         .p_sys       = p_spu_sys,
 319     };
 320     p_spu = decoder_NewSubpicture( p_dec, &updater );
 321     if( !p_spu )
 322     {
 323         msg_Warn( p_dec, "can't get spu buffer" );
 324         free( p_spu_sys );
 325         block_Release( p_block );
 326         return NULL;
 327     }
 328
 329     p_spu_sys->p_img = NULL;
 330     p_spu_sys->p_dec_sys = p_sys;
 331     p_spu_sys->i_subs_len = p_block->i_buffer;
 332     p_spu_sys->p_subs_data = malloc( p_block->i_buffer );
 333     p_spu_sys->i_pts = p_block->i_pts;
 334     if( !p_spu_sys->p_subs_data )
 335     {
 336         decoder_DeleteSubpicture( p_dec, p_spu );
 337         block_Release( p_block );
 338         return NULL;
 339     }
 340     memcpy( p_spu_sys->p_subs_data, p_block->p_buffer,
 341             p_block->i_buffer );
 342
 343     p_spu->i_start = p_block->i_pts;
 344     p_spu->i_stop = __MAX( p_sys->i_max_stop, p_block->i_pts + p_block->i_length );
 345     p_spu->b_ephemer = true;
 346     p_spu->b_absolute = true;
 347
 348     p_sys->i_max_stop = p_spu->i_stop;
 349
 350     vlc_mutex_lock( &p_sys->lock );
 351     if( p_sys->p_track )
 352     {
 353         ass_process_chunk( p_sys->p_track, p_spu_sys->p_subs_data, p_spu_sys->i_subs_len,
 354                            p_block->i_pts / 1000, p_block->i_length / 1000 );
 355     }
 356     vlc_mutex_unlock( &p_sys->lock );
 357
 358     DecSysHold( p_sys ); /* Keep a reference for the returned subpicture */
 359
 360     block_Release( p_block );
 361
 362     return p_spu;
 363 }
 364
 365 /****************************************************************************
 366  *
 367  ****************************************************************************/
 368 static int SubpictureValidate( subpicture_t *p_subpic,
 369                                bool b_fmt_src, const video_format_t *p_fmt_src,
 370                                bool b_fmt_dst, const video_format_t *p_fmt_dst,
 371                                mtime_t i_ts )
 372 {
 373     decoder_sys_t *p_sys = p_subpic->updater.p_sys->p_dec_sys;
 374
 375     vlc_mutex_lock( &p_sys->lock );
 376
 377     video_format_t fmt = *p_fmt_dst;
 378     fmt.i_chroma         = VLC_CODEC_RGBA;
 379     fmt.i_bits_per_pixel = 0;
 380     fmt.i_visible_width  = fmt.i_width;
 381     fmt.i_visible_height = fmt.i_height;
 382     fmt.i_x_offset       = 0;
 383     fmt.i_y_offset       = 0;
 384     if( b_fmt_src || b_fmt_dst )
 385     {
 386         ass_set_frame_size( p_sys->p_renderer, fmt.i_width, fmt.i_height );
 387         const double src_ratio = (double)p_fmt_src->i_width / p_fmt_src->i_height;
 388         const double dst_ratio = (double)p_fmt_dst->i_width / p_fmt_dst->i_height;
 389         ass_set_aspect_ratio( p_sys->p_renderer, dst_ratio / src_ratio, 1 );
 390         p_sys->fmt = fmt;
 391     }
 392
 393     /* */
 394     const mtime_t i_stream_date = p_subpic->updater.p_sys->i_pts + (i_ts - p_subpic->i_start);
 395     int i_changed;
 396     ASS_Image *p_img = ass_render_frame( p_sys->p_renderer, p_sys->p_track,
 397                                          i_stream_date/1000, &i_changed );
 398
 399     if( !i_changed && !b_fmt_src && !b_fmt_dst &&
 400         (p_img != NULL) == (p_subpic->p_region != NULL) )
 401     {
 402         vlc_mutex_unlock( &p_sys->lock );
 403         return VLC_SUCCESS;
 404     }
 405     p_subpic->updater.p_sys->p_img = p_img;
 406
 407     /* The lock is released by SubpictureUpdate */
 408     return VLC_EGENERIC;
 409 }
 410
 411 static void SubpictureUpdate( subpicture_t *p_subpic,
 412                               const video_format_t *p_fmt_src,
 413                               const video_format_t *p_fmt_dst,
 414                               mtime_t i_ts )
 415 {
 416     VLC_UNUSED( p_fmt_src ); VLC_UNUSED( p_fmt_dst ); VLC_UNUSED( i_ts );
 417
 418     decoder_sys_t *p_sys = p_subpic->updater.p_sys->p_dec_sys;
 419
 420     video_format_t fmt = p_sys->fmt;
 421     ASS_Image *p_img = p_subpic->updater.p_sys->p_img;
 422
 423     /* */
 424     p_subpic->i_original_picture_height = fmt.i_height;
 425     p_subpic->i_original_picture_width = fmt.i_width;
 426
 427     /* XXX to improve efficiency we merge regions that are close minimizing
 428      * the lost surface.
 429      * libass tends to create a lot of small regions and thus spu engine
 430      * reinstanciate a lot the scaler, and as we do not support subpel blending
 431      * it looks ugly (text unaligned).
 432      */
 433     const int i_max_region = 4;
 434     rectangle_t region[i_max_region];
 435     const int i_region = BuildRegions( region, i_max_region, p_img, fmt.i_width, fmt.i_height );
 436
 437     if( i_region <= 0 )
 438     {
 439         vlc_mutex_unlock( &p_sys->lock );
 440         return;
 441     }
 442
 443     /* Allocate the regions and draw them */
 444     subpicture_region_t **pp_region_last = &p_subpic->p_region;
 445
 446     for( int i = 0; i < i_region; i++ )
 447     {
 448         subpicture_region_t *r;
 449         video_format_t fmt_region;
 450
 451         /* */
 452         fmt_region = fmt;
 453         fmt_region.i_width =
 454         fmt_region.i_visible_width  = region[i].x1 - region[i].x0;
 455         fmt_region.i_height =
 456         fmt_region.i_visible_height = region[i].y1 - region[i].y0;
 457
 458         r = subpicture_region_New( &fmt_region );
 459         if( !r )
 460             break;
 461         r->i_x = region[i].x0;
 462         r->i_y = region[i].y0;
 463         r->i_align = SUBPICTURE_ALIGN_TOP | SUBPICTURE_ALIGN_LEFT;
 464
 465         /* */
 466         RegionDraw( r, p_img );
 467
 468         /* */
 469         *pp_region_last = r;
 470         pp_region_last = &r->p_next;
 471     }
 472     vlc_mutex_unlock( &p_sys->lock );
 473
 474 }
 475 static void SubpictureDestroy( subpicture_t *p_subpic )
 476 {
 477     subpicture_updater_sys_t *p_sys = p_subpic->updater.p_sys;
 478
 479     DecSysRelease( p_sys->p_dec_sys );
 480     free( p_sys->p_subs_data );
 481     free( p_sys );
 482 }
 483
 484 static rectangle_t r_create( int x0, int y0, int x1, int y1 )
 485 {
 486     rectangle_t r = { x0, y0, x1, y1 };
 487     return r;
 488 }
 489 static rectangle_t r_img( const ASS_Image *p_img )
 490 {
 491     return r_create( p_img->dst_x, p_img->dst_y, p_img->dst_x+p_img->w, p_img->dst_y+p_img->h );
 492 }
 493 static void r_add( rectangle_t *r, const rectangle_t *n )
 494 {
 495     r->x0 = __MIN( r->x0, n->x0 );
 496     r->y0 = __MIN( r->y0, n->y0 );
 497     r->x1 = __MAX( r->x1, n->x1 );
 498     r->y1 = __MAX( r->y1, n->y1 );
 499 }
 500 static int r_surface( const rectangle_t *r )
 501 {
 502     return (r->x1-r->x0) * (r->y1-r->y0);
 503 }
 504 static bool r_overlap( const rectangle_t *a, const rectangle_t *b, int i_dx, int i_dy )
 505 {
 506     return  __MAX(a->x0-i_dx, b->x0) < __MIN( a->x1+i_dx, b->x1 ) &&
 507             __MAX(a->y0-i_dy, b->y0) < __MIN( a->y1+i_dy, b->y1 );
 508 }
 509
 510 static int BuildRegions( rectangle_t *p_region, int i_max_region, ASS_Image *p_img_list, int i_width, int i_height )
 511 {
 512     ASS_Image *p_tmp;
 513     int i_count;
 514
 515 #ifdef DEBUG_REGION
 516     int64_t i_ck_start = mdate();
 517 #endif
 518
 519     for( p_tmp = p_img_list, i_count = 0; p_tmp != NULL; p_tmp = p_tmp->next )
 520         if( p_tmp->w > 0 && p_tmp->h > 0 )
 521             i_count++;
 522     if( i_count <= 0 )
 523         return 0;
 524
 525     ASS_Image **pp_img = calloc( i_count, sizeof(*pp_img) );
 526     if( !pp_img )
 527         return 0;
 528
 529     for( p_tmp = p_img_list, i_count = 0; p_tmp != NULL; p_tmp = p_tmp->next )
 530         if( p_tmp->w > 0 && p_tmp->h > 0 )
 531             pp_img[i_count++] = p_tmp;
 532
 533     /* */
 534     const int i_w_inc = __MAX( ( i_width + 49 ) / 50, 32 );
 535     const int i_h_inc = __MAX( ( i_height + 99 ) / 100, 32 );
 536     int i_maxh = i_w_inc;
 537     int i_maxw = i_h_inc;
 538     int i_region;
 539     rectangle_t region[i_max_region+1];
 540
 541     i_region = 0;
 542     for( int i_used = 0; i_used < i_count; )
 543     {
 544         int n;
 545         for( n = 0; n < i_count; n++ )
 546         {
 547             if( pp_img[n] )
 548                 break;
 549         }
 550         assert( i_region < i_max_region + 1 );
 551         region[i_region++] = r_img( pp_img[n] );
 552         pp_img[n] = NULL; i_used++;
 553
 554         bool b_ok;
 555         do {
 556             b_ok = false;
 557             for( n = 0; n < i_count; n++ )
 558             {
 559                 ASS_Image *p_img = pp_img[n];
 560                 if( !p_img )
 561                     continue;
 562                 rectangle_t r = r_img( p_img );
 563
 564                 int k;
 565                 int i_best = -1;
 566                 int i_best_s = INT_MAX;
 567                 for( k = 0; k < i_region; k++ )
 568                 {
 569                     if( !r_overlap( &region[k], &r, i_maxw, i_maxh ) )
 570                         continue;
 571                     int s = r_surface( &r );
 572                     if( s < i_best_s )
 573                     {
 574                         i_best_s = s;
 575                         i_best = k;
 576                     }
 577                 }
 578                 if( i_best >= 0 )
 579                 {
 580                     r_add( &region[i_best], &r );
 581                     pp_img[n] = NULL; i_used++;
 582                     b_ok = true;
 583                 }
 584             }
 585         } while( b_ok );
 586
 587         if( i_region > i_max_region )
 588         {
 589             int i_best_i = -1;
 590             int i_best_j = -1;
 591             int i_best_ds = INT_MAX;
 592
 593             /* merge best */
 594             for( int i = 0; i < i_region; i++ )
 595             {
 596                 for( int j = i+1; j < i_region; j++ )
 597                 {
 598                     rectangle_t n = region[i];
 599                     r_add( &n, &region[j] );
 600                     int ds = r_surface( &n ) - r_surface( &region[i] ) - r_surface( &region[j] );
 601
 602                     if( ds < i_best_ds )
 603                     {
 604                         i_best_i = i;
 605                         i_best_j = j;
 606                         i_best_ds = ds;
 607                     }
 608                 }
 609             }
 610 #ifdef DEBUG_REGION
 611             msg_Err( p_spu, "Merging %d and %d", i_best_i, i_best_j );
 612 #endif
 613             r_add( &region[i_best_i], &region[i_best_j] );
 614
 615             if( i_best_j+1 < i_region )
 616                 memmove( &region[i_best_j], &region[i_best_j+1], sizeof(*region) * ( i_region - (i_best_j+1)  ) );
 617             i_region--;
 618         }
 619     }
 620
 621     /* */
 622     for( int n = 0; n < i_region; n++ )
 623         p_region[n] = region[n];
 624
 625 #ifdef DEBUG_REGION
 626     int64_t i_ck_time = mdate() - i_ck_start;
 627     msg_Err( p_spu, "ASS: %d objects merged into %d region in %d micros", i_count, i_region, (int)(i_ck_time) );
 628 #endif
 629
 630     free( pp_img );
 631
 632     return i_region;
 633 }
 634
 635 static void RegionDraw( subpicture_region_t *p_region, ASS_Image *p_img )
 636 {
 637     const plane_t *p = &p_region->p_picture->p[0];
 638     const int i_x = p_region->i_x;
 639     const int i_y = p_region->i_y;
 640     const int i_width  = p_region->fmt.i_width;
 641     const int i_height = p_region->fmt.i_height;
 642
 643     memset( p->p_pixels, 0x00, p->i_pitch * p->i_lines );
 644     for( ; p_img != NULL; p_img = p_img->next )
 645     {
 646         if( p_img->dst_x < i_x || p_img->dst_x + p_img->w > i_x + i_width ||
 647             p_img->dst_y < i_y || p_img->dst_y + p_img->h > i_y + i_height )
 648             continue;
 649
 650         const unsigned r = (p_img->color >> 24)&0xff;
 651         const unsigned g = (p_img->color >> 16)&0xff;
 652         const unsigned b = (p_img->color >>  8)&0xff;
 653         const unsigned a = (p_img->color      )&0xff;
 654         int x, y;
 655
 656         for( y = 0; y < p_img->h; y++ )
 657         {
 658             for( x = 0; x < p_img->w; x++ )
 659             {
 660                 const unsigned alpha = p_img->bitmap[y*p_img->stride+x];
 661                 const unsigned an = (255 - a) * alpha / 255;
 662
 663                 uint8_t *p_rgba = &p->p_pixels[(y+p_img->dst_y-i_y) * p->i_pitch + 4 * (x+p_img->dst_x-i_x)];
 664                 const unsigned ao = p_rgba[3];
 665
 666                 /* Native endianness, but RGBA ordering */
 667                 if( ao == 0 )
 668                 {
 669                     /* Optimized but the else{} will produce the same result */
 670                     p_rgba[0] = r;
 671                     p_rgba[1] = g;
 672                     p_rgba[2] = b;
 673                     p_rgba[3] = an;
 674                 }
 675                 else
 676                 {
 677                     p_rgba[3] = 255 - ( 255 - p_rgba[3] ) * ( 255 - an ) / 255;
 678                     if( p_rgba[3] != 0 )
 679                     {
 680                         p_rgba[0] = ( p_rgba[0] * ao * (255-an) / 255 + r * an ) / p_rgba[3];
 681                         p_rgba[1] = ( p_rgba[1] * ao * (255-an) / 255 + g * an ) / p_rgba[3];
 682                         p_rgba[2] = ( p_rgba[2] * ao * (255-an) / 255 + b * an ) / p_rgba[3];
 683                     }
 684                 }
 685             }
 686         }
 687     }
 688
 689 #ifdef DEBUG_REGION
 690     /* XXX Draw a box for debug */
 691 #define P(x,y) ((uint32_t*)&p->p_pixels[(y)*p->i_pitch + 4*(x)])
 692     for( int y = 0; y < p->i_lines; y++ )
 693         *P(0,y) = *P(p->i_visible_pitch/4-1,y) = 0xff000000;
 694     for( int x = 0; x < p->i_visible_pitch; x++ )
 695         *P(x/4,0) = *P(x/4,p->i_visible_lines-1) = 0xff000000;
 696 #undef P
 697 #endif
 698 }
 699