research.m1stereo.tv/gitweb/ - melted/blob - src/modules/vmfx/filter_chroma.c

   1 /*
   2  * filter_chroma.c -- Maps a chroma key to the alpha channel
   3  * Copyright (C) 2005 Visual Media Fx Inc.
   4  * Author: Charles Yates <charles.yates@pandora.be>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19  */
  20
  21 #include <framework/mlt_filter.h>
  22 #include <stdlib.h>
  23 #include <math.h>
  24 #include <framework/mlt_factory.h>
  25 #include <framework/mlt_frame.h>
  26 #include <framework/mlt_producer.h>
  27 #include <framework/mlt_geometry.h>
  28
  29 static inline int in_range( uint8_t v, uint8_t c, int var )
  30 {
  31         return ( ( int )v >= c - var ) && ( ( int )v <= c + var );
  32 }
  33
  34 static inline uint8_t alpha_value( uint8_t a, uint8_t *p, uint8_t u, uint8_t v, int var, int odd )
  35 {
  36         if ( odd == 0 )
  37                 return ( in_range( *( p + 1 ), u, var ) && in_range( *( p + 3 ), v, var ) ) ? 0 : a;
  38         else
  39                 return ( in_range( ( *( p + 1 ) + *( p + 5 ) ) / 2, u, var ) && in_range( ( *( p + 3 ) + *( p + 7 ) ) / 2, v, var ) ) ? 0 : a;
  40 }
  41
  42 /** Get the images and map the chroma to the alpha of the frame.
  43 */
  44
  45 static int filter_get_image( mlt_frame frame, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
  46 {
  47         mlt_filter this = mlt_frame_pop_service( frame );
  48         int variance = 200 * mlt_properties_get_double( MLT_FILTER_PROPERTIES( this ), "variance" );
  49         int32_t key_val = mlt_properties_get_int( MLT_FILTER_PROPERTIES( this ), "key" );
  50         uint8_t r = ( key_val >> 24 ) & 0xff;
  51         uint8_t g = ( key_val >> 16 ) & 0xff;
  52         uint8_t b = ( key_val >>  8 ) & 0xff;
  53         uint8_t y, u, v;
  54
  55         RGB2YUV( r, g, b, y, u, v );
  56
  57         if ( mlt_frame_get_image( frame, image, format, width, height, writable ) == 0 )
  58         {
  59                 uint8_t *alpha = mlt_frame_get_alpha_mask( frame );
  60                 uint8_t *p = *image;
  61                 int size = *width * *height / 2;
  62                 while ( size -- )
  63                 {
  64                         *alpha = alpha_value( *alpha, p, u, v, variance, 0 );
  65                         alpha ++;
  66                         *alpha = alpha_value( *alpha, p, u, v, variance, 1 );
  67                         alpha ++;
  68                         p += 4;
  69                 }
  70         }
  71
  72         return 0;
  73 }
  74
  75 /** Filter processing.
  76 */
  77
  78 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
  79 {
  80         mlt_frame_push_service( frame, this );
  81         mlt_frame_push_service( frame, filter_get_image );
  82         return frame;
  83 }
  84
  85 /** Constructor for the filter.
  86 */
  87
  88 mlt_filter filter_chroma_init( mlt_profile profile, mlt_service_type type, const char *id, char *arg )
  89 {
  90         mlt_filter this = mlt_filter_new( );
  91         if ( this != NULL )
  92         {
  93                 mlt_properties_set( MLT_FILTER_PROPERTIES( this ), "key", arg == NULL ? "0x0000ff00" : arg );
  94                 mlt_properties_set_double( MLT_FILTER_PROPERTIES( this ), "variance", 0.15 );
  95                 this->process = filter_process;
  96         }
  97         return this;
  98 }
  99