[vlc-devel] [PATCH] Extracted sobel oeprator into its own function and simplified help message
Tristan Matthews
tmatth at videolan.org
Tue Feb 2 12:10:38 CET 2016
Hi,
On Wed, Jan 27, 2016 at 5:50 PM, Odd-Arild Kristensen
<oddarildkristensen at gmail.com> wrote:
> ---
> modules/video_filter/Makefile.am | 3 +
> modules/video_filter/edgedetection.c | 218 +++++++++++++++++++++++++++++++++++
> 2 files changed, 221 insertions(+)
> create mode 100644 modules/video_filter/edgedetection.c
>
> diff --git a/modules/video_filter/Makefile.am b/modules/video_filter/Makefile.am
> index ea0b72c..b2ff9cd 100644
> --- a/modules/video_filter/Makefile.am
> +++ b/modules/video_filter/Makefile.am
> @@ -3,6 +3,8 @@ video_filterdir = $(pluginsdir)/video_filter
> noinst_HEADERS += video_filter/filter_picture.h
>
> # video filters
> +libedgedetection_plugin_la_SOURCES = video_filter/edgedetection.c
> +libedgedetection_plugin_la_LIBADD = $(LIBM)
> libadjust_plugin_la_SOURCES = video_filter/adjust.c video_filter/adjust_sat_hue.c video_filter/adjust_sat_hue.h
> libadjust_plugin_la_LIBADD = $(LIBM)
> libalphamask_plugin_la_SOURCES = video_filter/alphamask.c
> @@ -75,6 +77,7 @@ video_filter_LTLIBRARIES = \
> libcanvas_plugin.la \
> libcolorthres_plugin.la \
> libcroppadd_plugin.la \
> + libedgedetection_plugin.la \
> liberase_plugin.la \
> libextract_plugin.la \
> libgradient_plugin.la \
> diff --git a/modules/video_filter/edgedetection.c b/modules/video_filter/edgedetection.c
> new file mode 100644
> index 0000000..dce0064
> --- /dev/null
> +++ b/modules/video_filter/edgedetection.c
> @@ -0,0 +1,218 @@
> +/******************************************************************************
> + * edgedetection.c : edge detection plugin for VLC
> + *****************************************************************************
> + * Copyright (C) 2016 VLC authors and VideoLAN
> + * $Id$
> + *
> + * Authors: Odd-Arild Kristensen <oddarildkristensen at gmail.com>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU Lesser General Public License as published by
> + * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with this program; if not, write to the Free Software Foundation,
> + * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
> + *****************************************************************************/
> +
> +/*****************************************************************************
> + * Preabmle
> + *****************************************************************************/
> +#ifdef HAVE_CONFIG_H
> +# include "config.h"
> +#endif
> +
> +#include <assert.h>
> +#include <vlc_common.h>
> +#include <vlc_plugin.h>
> +#include <vlc_filter.h>
> +#include <string.h>
> +
> +/*****************************************************************************
> + * Module descriptor
> + *****************************************************************************/
> +#define EDGE_DETECTION_DESCRIPTION N_( "Edge detection video filter" )
> +#define EDGE_DETECTION_TEXT N_( "Edge detection" )
> +#define EDGE_DETECTION_LONGTEXT N_( \
> + "Detects edges in the frame and highlights them in white." )
> +
> +/*****************************************************************************
> + * Local prototypes
> + *****************************************************************************/
> +static int Open( vlc_object_t * );
> +static int Close( vlc_object_t * );
> +static picture_t *new_frame( filter_t * );
> +static picture_t *Filter( filter_t *, picture_t * );
> +static int sobel( uint8_t const *, const int, const int, const int, const int);
> +
> +/* Kernel for X axis */
> +static const int pi_kernel_x[3][3] = {
> + {-1, 0, 1},
> + {-2, 0, 2},
> + {-1, 0, 1}
> +};
> +
> +/* Kernel for Y axis */
> +static const int pi_kernel_y[3][3] = {
> + {-1, -2, -1},
> + {0, 0, 0},
> + {1, 2, 1}
> +};
> +
> +vlc_module_begin ()
> +
> + set_description( EDGE_DETECTION_DESCRIPTION )
> + set_shortname( EDGE_DETECTION_TEXT )
> + set_help( EDGE_DETECTION_LONGTEXT )
> + set_category( CAT_VIDEO )
> + set_subcategory( SUBCAT_VIDEO_VFILTER )
> +
> + set_capability( "video filter2", 0 )
> + set_callbacks( Open, Close )
> +
> +vlc_module_end ()
> +
> +/* Store the filter chain */
> +struct filter_sys_t
> +{
> + filter_chain_t *p_chain;
> +};
> +
> +/*****************************************************************************
> + * Opens the filter.
> + * Sets up the filer chain. The image needs to be black-and-white in order to
> + * detect any edges. The Gaussian blur is needed so that the Sobel operator
> + * does not give a high response for noise, or small changes in the image.
> + *****************************************************************************/
> +static int Open( vlc_object_t *p_this )
> +{
> + es_format_t fmt;
> + filter_t *p_filter = (filter_t *)p_this;
> + filter_sys_t *p_sys;
> + filter_owner_t owner = {
> + .sys = p_filter,
> + .video = {
> + .buffer_new = new_frame,
> + },
> + };
> +
> + p_sys = malloc( sizeof( filter_sys_t ) );
> + if( p_sys == NULL) {
> + return VLC_ENOMEM;
> + }
> +
> + p_filter->p_sys = p_sys;
> + p_filter->p_sys->p_chain = filter_chain_NewVideo( p_filter, true, &owner );
> +
> + if ( p_sys->p_chain == NULL)
> + {
> + msg_Err( p_filter, "Could not allocate filter chain" );
> + free( p_sys );
> + return VLC_EGENERIC;
> + }
> + es_format_Copy( &fmt, &p_filter->fmt_in );
> + /* Clear filter chain */
> + filter_chain_Reset( p_sys->p_chain, &p_filter->fmt_in, &fmt);
> + /* Add adjust filter to turn frame black-and-white */
> + filter_chain_AppendFromString( p_sys->p_chain, "adjust{saturation=0}" );
> + /* Add gaussian blur to the frame so to remove some noise in the frame,
> + which reduces the number 'random' of lines being enhanced. */
nit: "Add gaussian blur to the frame so as to remove some noise, which
reduces the number of 'random' lines being enhanced."
> + filter_chain_AppendFromString( p_sys->p_chain, "gaussianblur{deviation=1}" );
filter_chain_AppendFromString can return NULL, you'll want to check
both of these calls.
> + // fmt = *filter_chain_GetFmtOut( p_filter->p_sys->p_chain );
You can delete this line.
> + /* Set callback function */
> + p_filter->pf_video_filter = Filter;
> + return VLC_SUCCESS;
> +}
> +
> +/******************************************************************************
> + * Closes the filter and cleans up all dynamically allocated data.
> + ******************************************************************************/
> +static int Close( vlc_object_t *p_this )
> +{
> + filter_t *p_filter = (filter_t *)p_this;
I believe you need to call filter_chainDelete on your chain here as
well (see e.g., the canvas filter)
> + free( p_filter->p_sys );
> + return VLC_SUCCESS;
> +}
> +
> +/* *****************************************************************************
> + * Allocates a new buffer for the filter chain.
> + ******************************************************************************/
> +static picture_t *new_frame( filter_t *p_filter)
> +{
> + return filter_NewPicture( p_filter->owner.sys );
> +}
> +
> +/******************************************************************************
> + * Callback function.
> + * This function implements the sobel operator which can be used to detect
> + * edges in a black-and-white image. The sobel operator is applied to
> + * every pixel in the frame for both X and Y axis.
> + ******************************************************************************/
> +static picture_t *Filter( filter_t *p_filter, picture_t *p_pic )
> +{
> + picture_t *p_filtered_frame =
> + filter_chain_VideoFilter( p_filter->p_sys->p_chain, p_pic );
> + picture_t *p_out_frame = picture_NewFromFormat( &p_pic->format );
> + if ( p_out_frame == NULL )
> + {
> + msg_Err( p_filter, "Could not allocate memory for new frame" );
> + return NULL;
> + }
> + const int i_lines = p_filtered_frame->p[Y_PLANE].i_visible_lines;
> + const int i_pitch = p_filtered_frame->p[Y_PLANE].i_pitch;
> + /* Loop through every pixel in the frame */
> + for ( int i_line = 1; i_line < i_lines - 1; i_line++ )
> + {
> + for ( int i_col = 1; i_col < i_pitch - 1; i_col++ )
> + {
> + /* Set the new value for the pixel */
> + *( p_out_frame->p[Y_PLANE].p_pixels + ((i_pitch * i_line) + i_col) ) =
> + (uint8_t) sobel( p_filtered_frame->p[Y_PLANE].p_pixels,
> + i_pitch, i_lines, i_col, i_line );
> + }
> + }
> + picture_Release( p_filtered_frame );
> + return p_out_frame;
> +}
> +
> +/******************************************************************************
> + * Sobel Operator.
> + * Calculates the gradients for both X and Y directions in a frame.
> + ******************************************************************************/
> +static int sobel( uint8_t const *p_pixels, const int i_pitch, const int i_lines,
> + const int i_col, const int i_line )
> +{
> + int i_x_val = 0;
> + int i_y_val = 0;
> + /* Check for frame boundry */
"boundary"
> + if ( i_line == 0 || i_line == i_lines )
> + {
> + i_y_val = 0;
> + }
> + else if( i_col == 0 || i_col == i_pitch )
> + {
> + i_x_val = 0;
> + }
> + /* General case where Sobel operator is applied */
> + else
> + {
> + /* Apply the kernel to the pixel */
> + for ( int i_x = 0; i_x < 3; i_x++ )
> + {
> + for ( int i_y = 0; i_y < 3; i_y++ )
> + {
> + i_x_val += pi_kernel_x[i_x][i_y] *
> + p_pixels[i_pitch * (i_line + i_y - 1) + (i_col + i_x - 1)];
> + i_y_val += pi_kernel_y[i_x][i_y] *
> + p_pixels[i_pitch * (i_line + i_y + 1) + (i_col + i_x - 1)];
> + }
> + }
> + }
> + return abs(i_x_val) + abs(i_y_val);
> +}
> --
> 2.2.0
>
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Also 'operator' is misspelled in the subject line.
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