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 library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library 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 GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include <framework/mlt_filter.h>
  22 #include <framework/mlt_frame.h>
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <math.h>
  27
  28 /** Do it :-).
  29 */
  30
  31 static int filter_get_image( mlt_frame this, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
  32 {
  33         int error = mlt_frame_get_image( this, image, format, width, height, 1 );
  34
  35         if ( error == 0 && *format == mlt_image_yuv422 )
  36         {
  37                 // Get the gamma value
  38                 double gamma = mlt_properties_get_double( MLT_FRAME_PROPERTIES( this ), "gamma" );
  39
  40                 if ( gamma != 1.0 )
  41                 {
  42                         uint8_t *p = *image;
  43                         uint8_t *q = *image + *width * *height * 2;
  44
  45                         // Calculate the look up table
  46                         double exp = 1 / gamma;
  47                         uint8_t lookup[ 256 ];
  48                         int i;
  49
  50                         for( i = 0; i < 256; i ++ )
  51                                 lookup[ i ] = ( uint8_t )( pow( ( double )i / 255.0, exp ) * 255 );
  52
  53                         while ( p != q )
  54                         {
  55                                 *p = lookup[ *p ];
  56                                 p += 2;
  57                         }
  58                 }
  59         }
  60
  61         return 0;
  62 }
  63
  64 /** Filter processing.
  65 */
  66
  67 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
  68 {
  69         double gamma = mlt_properties_get_double( MLT_FILTER_PROPERTIES( this ), "gamma" );
  70         gamma = gamma <= 0 ? 1 : gamma;
  71         mlt_properties_set_double( MLT_FRAME_PROPERTIES( frame ), "gamma", gamma );
  72         mlt_frame_push_get_image( frame, filter_get_image );
  73         return frame;
  74 }
  75
  76 /** Constructor for the filter.
  77 */
  78
  79 mlt_filter filter_gamma_init( mlt_profile profile, mlt_service_type type, const char *id, char *arg )
  80 {
  81         mlt_filter this = mlt_filter_new( );
  82         if ( this != NULL )
  83         {
  84                 this->process = filter_process;
  85                 mlt_properties_set( MLT_FILTER_PROPERTIES( this ), "gamma", arg == NULL ? "1" : arg );
  86         }
  87         return this;
  88 }