research.m1stereo.tv/gitweb/ - melted/blob - mlt/src/modules/core/filter_gamma.c

   1 /*
   2  * filter_gamma.c -- gamma filter
   3  * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
   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 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 General Public License for more details.
  15  *
  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.
  19  */
  20
  21 #include "filter_gamma.h"
  22
  23 #include <framework/mlt_frame.h>
  24
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <math.h>
  28
  29 /** Do it :-).
  30 */
  31
  32 static int filter_get_image( mlt_frame this, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
  33 {
  34         mlt_frame_get_image( this, image, format, width, height, 1 );
  35         uint8_t *p = *image;
  36         uint8_t *q = *image + *width * *height * 2;
  37
  38         // Get the gamma value
  39         double gamma = mlt_properties_get_double( mlt_frame_properties( this ), "gamma" );
  40
  41         // Calculate the look up table
  42         double exp = 1 / gamma;
  43         uint8_t lookup[ 256 ];
  44         int i;
  45
  46         for( i = 0; i < 256; i ++ )
  47                 lookup[ i ] = ( uint8_t )( pow( ( double )i / 255.0, exp ) * 255 );
  48
  49         while ( p != q )
  50         {
  51                 *p = lookup[ *p ];
  52                 p += 2;
  53         }
  54
  55         return 0;
  56 }
  57
  58 /** Filter processing.
  59 */
  60
  61 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
  62 {
  63         double gamma = mlt_properties_get_double( mlt_filter_properties( this ), "gamma" );
  64         gamma = gamma <= 0 ? 2 : gamma;
  65         mlt_frame_push_get_image( frame, filter_get_image );
  66         mlt_properties_set_double( mlt_frame_properties( frame ), "gamma", gamma );
  67         return frame;
  68 }
  69
  70 /** Constructor for the filter.
  71 */
  72
  73 mlt_filter filter_gamma_init( char *arg )
  74 {
  75         mlt_filter this = calloc( sizeof( struct mlt_filter_s ), 1 );
  76         if ( this != NULL )
  77         {
  78                 mlt_filter_init( this, NULL );
  79                 this->process = filter_process;
  80                 if ( arg != NULL )
  81                         mlt_properties_set_double( mlt_filter_properties( this ), "gamma", atof( arg ) );
  82         }
  83         return this;
  84 }
  85