research.m1stereo.tv/gitweb/ - melted/blob - 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         int error = mlt_frame_get_image( this, image, format, width, height, 1 );
  35
  36         if ( error == 0 && *format == mlt_image_yuv422 )
  37         {
  38                 // Get the gamma value
  39                 double gamma = mlt_properties_get_double( mlt_frame_properties( this ), "gamma" );
  40
  41                 if ( gamma != 1.0 )
  42                 {
  43                         uint8_t *p = *image;
  44                         uint8_t *q = *image + *width * *height * 2;
  45
  46                         // Calculate the look up table
  47                         double exp = 1 / gamma;
  48                         uint8_t lookup[ 256 ];
  49                         int i;
  50
  51                         for( i = 0; i < 256; i ++ )
  52                                 lookup[ i ] = ( uint8_t )( pow( ( double )i / 255.0, exp ) * 255 );
  53
  54                         while ( p != q )
  55                         {
  56                                 *p = lookup[ *p ];
  57                                 p += 2;
  58                         }
  59                 }
  60         }
  61
  62         return 0;
  63 }
  64
  65 /** Filter processing.
  66 */
  67
  68 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
  69 {
  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 );
  74         return frame;
  75 }
  76
  77 /** Constructor for the filter.
  78 */
  79
  80 mlt_filter filter_gamma_init( char *arg )
  81 {
  82         mlt_filter this = mlt_filter_new( );
  83         if ( this != NULL )
  84         {
  85                 this->process = filter_process;
  86                 mlt_properties_set( mlt_filter_properties( this ), "gamma", arg == NULL ? "1" : arg );
  87         }
  88         return this;
  89 }