+/*
+ * filter_chroma.c -- Maps a chroma key to the alpha channel
+ * Copyright (C) 2005 Visual Media Fx Inc.
+ * Author: Charles Yates <charles.yates@pandora.be>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include "filter_chroma.h"
+#include <stdlib.h>
+#include <framework/mlt_factory.h>
+#include <framework/mlt_frame.h>
+#include <framework/mlt_producer.h>
+#include <framework/mlt_geometry.h>
+
+static inline int in_range( uint8_t v, uint8_t c, int var )
+{
+ return ( v >= c - var ) && ( v <= c + var );
+}
+
+static inline uint8_t alpha_value( uint8_t a, uint8_t *p, uint8_t u, uint8_t v, int var )
+{
+ return ( in_range( *( p + 1 ), u, var ) && in_range( *( p + 3 ), v, var ) ) ? 0 : a;
+}
+
+/** Get the images and map the chroma to the alpha of the frame.
+*/
+
+static int filter_get_image( mlt_frame frame, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
+{
+ mlt_filter this = mlt_frame_pop_service( frame );
+ char *key = mlt_properties_get( MLT_FILTER_PROPERTIES( this ), "key" );
+ int variance = 255 * mlt_properties_get_double( MLT_FILTER_PROPERTIES( this ), "variance" ) + 0.5;
+ int32_t key_val = strtol( key, &key, 0 );
+ uint8_t b = key_val & 0xff;
+ uint8_t g = ( key_val >> 8 ) & 0xff;
+ uint8_t r = ( key_val >> 16 ) & 0xff;
+ uint8_t y, u, v;
+
+ RGB2YUV( r, g, b, y, u, v );
+
+ if ( mlt_frame_get_image( frame, image, format, width, height, writable ) == 0 )
+ {
+ uint8_t *alpha = mlt_frame_get_alpha_mask( frame );
+ uint8_t *p = *image;
+ int size = *width * *height;
+ int odd = 0;
+ while ( size -- )
+ {
+ *alpha = alpha_value( *alpha, p, u, v, variance );
+ if ( odd ) p += 4;
+ odd = !odd;
+ alpha ++;
+ }
+ }
+
+ return 0;
+}
+
+/** Filter processing.
+*/
+
+static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
+{
+ mlt_frame_push_service( frame, this );
+ mlt_frame_push_service( frame, filter_get_image );
+ return frame;
+}
+
+/** Constructor for the filter.
+*/
+
+mlt_filter filter_chroma_init( char *arg )
+{
+ mlt_filter this = mlt_filter_new( );
+ if ( this != NULL )
+ {
+ mlt_properties_set( MLT_FILTER_PROPERTIES( this ), "key", arg == NULL ? "0x00ff00" : arg );
+ mlt_properties_set_double( MLT_FILTER_PROPERTIES( this ), "variance", 0.3 );
+ this->process = filter_process;
+ }
+ return this;
+}
+