research.m1stereo.tv/gitweb/ - melted/blob - src/modules/vmfx/filter_chroma_hold.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 "filter_chroma.h"
  22 #include <stdlib.h>
  23 #include <framework/mlt_factory.h>
  24 #include <framework/mlt_frame.h>
  25 #include <framework/mlt_producer.h>
  26 #include <framework/mlt_geometry.h>
  27
  28 static inline int in_range( uint8_t v, uint8_t c, int var )
  29 {
  30         return ( ( int )v >= c - var ) && ( ( int )v <= c + var );
  31 }
  32
  33 static inline uint8_t alpha_value( uint8_t a, uint8_t *p, uint8_t u, uint8_t v, int var )
  34 {
  35         return ( in_range( *( p + 1 ), u, var ) && in_range( *( p + 3 ), v, var ) ) ? 0 : a;
  36 }
  37
  38 /** Get the images and map the chroma to the alpha of the frame.
  39 */
  40
  41 static int filter_get_image( mlt_frame frame, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
  42 {
  43         mlt_filter this = mlt_frame_pop_service( frame );
  44         char *key = mlt_properties_get( MLT_FILTER_PROPERTIES( this ), "key" );
  45         int variance = 200 * mlt_properties_get_double( MLT_FILTER_PROPERTIES( this ), "variance" );
  46         int32_t key_val = strtol( key, &key, 0 );
  47         uint8_t b = key_val & 0xff;
  48         uint8_t g = ( key_val >> 8 ) & 0xff;
  49         uint8_t r = ( key_val >> 16 ) & 0xff;
  50         uint8_t y, u, v;
  51
  52         RGB2YUV( r, g, b, y, u, v );
  53
  54         if ( mlt_frame_get_image( frame, image, format, width, height, writable ) == 0 )
  55         {
  56                 uint8_t alpha = 0;
  57                 uint8_t *p = *image;
  58                 int size = *width * *height / 2;
  59                 while ( size -- )
  60                 {
  61                         alpha = alpha_value( 255, p, u, v, variance );
  62                         p ++;
  63                         if ( alpha )
  64                                 *p ++ = 128;
  65                         else
  66                                 p ++;
  67                         alpha = alpha_value( 255, p, v, u, variance );
  68                         p ++;
  69                         if ( alpha )
  70                                 *p ++ = 128;
  71                         else
  72                                 p ++;
  73                 }
  74         }
  75
  76         return 0;
  77 }
  78
  79 /** Filter processing.
  80 */
  81
  82 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
  83 {
  84         mlt_frame_push_service( frame, this );
  85         mlt_frame_push_service( frame, filter_get_image );
  86         return frame;
  87 }
  88
  89 /** Constructor for the filter.
  90 */
  91
  92 mlt_filter filter_chroma_hold_init( char *arg )
  93 {
  94         mlt_filter this = mlt_filter_new( );
  95         if ( this != NULL )
  96         {
  97                 mlt_properties_set( MLT_FILTER_PROPERTIES( this ), "key", arg == NULL ? "0xc00000" : arg );
  98                 mlt_properties_set_double( MLT_FILTER_PROPERTIES( this ), "variance", 0.3 );
  99                 this->process = filter_process;
 100         }
 101         return this;
 102 }
 103