2 * filter_gamma.c -- gamma filter
3 * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
4 * Author: Charles Yates <charles.yates@pandora.be>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU 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.
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 General Public License for more details.
16 * You should have received a copy of the GNU 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.
21 #include "filter_gamma.h"
23 #include <framework/mlt_frame.h>
32 static int filter_get_image( mlt_frame this, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
34 int error = mlt_frame_get_image( this, image, format, width, height, 1 );
36 if ( error != 0 && *format == mlt_image_yuv422 )
38 // Get the gamma value
39 double gamma = mlt_properties_get_double( mlt_frame_properties( this ), "gamma" );
44 uint8_t *q = *image + *width * *height * 2;
46 // Calculate the look up table
47 double exp = 1 / gamma;
48 uint8_t lookup[ 256 ];
51 for( i = 0; i < 256; i ++ )
52 lookup[ i ] = ( uint8_t )( pow( ( double )i / 255.0, exp ) * 255 );
65 /** Filter processing.
68 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
70 double gamma = mlt_properties_get_double( mlt_filter_properties( this ), "gamma" );
71 gamma = gamma <= 0 ? 1 : gamma;
72 mlt_properties_set_double( mlt_frame_properties( frame ), "gamma", gamma );
73 mlt_frame_push_get_image( frame, filter_get_image );
77 /** Constructor for the filter.
80 mlt_filter filter_gamma_init( char *arg )
82 mlt_filter this = mlt_filter_new( );
85 this->process = filter_process;
86 mlt_properties_set( mlt_filter_properties( this ), "gamma", arg == NULL ? "1" : arg );