[sdf -> bsdf] Added function to approximate edge distance.
* src/sdf/ftbsdf.c (bsdf_approximate_edge): The function uses the Gustavson's algorithm to approximate the edge from pixel values. * src/sdf/ftbsdf.c (compute_gradient): The function uses Sobel's operator to compute the gradient at a pixel. The is used to detect edge direction.
This commit is contained in:
Anuj Verma
anujverma
parent
ffb6890089
commit
fbbec7c64d
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@ -1,3 +1,15 @@
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2020-07-29 Anuj Verma <anujv@iitbhilai.ac.in>
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[sdf -> bsdf] Added function to approximate edge distance.
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* src/sdf/ftbsdf.c (bsdf_approximate_edge): The function
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uses the Gustavson's algorithm to approximate the edge
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from pixel values.
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* src/sdf/ftbsdf.c (compute_gradient): The function uses
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Sobel's operator to compute the gradient at a pixel.
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The is used to detect edge direction.
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2020-07-28 Anuj Verma <anujv@iitbhilai.ac.in>
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* src/sdf/ftbsdf.c (_pass): Use function for repetitive task.
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159
src/sdf/ftbsdf.c
159
src/sdf/ftbsdf.c
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@ -47,7 +47,8 @@
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} BSDF_TRaster;
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/* euclidean distance used for euclidean distance transform */
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/* Euclidean distance used for euclidean distance transform */
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/* can also be interpreted as edge distance. */
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typedef struct ED_
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{
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FT_16D16 dist; /* distance at `near' */
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@ -121,17 +122,20 @@
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FT_Int w, /* width */
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FT_Int r ) /* rows */
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{
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FT_Bool is_edge = 0;
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FT_Bool is_edge = 0;
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FT_Byte* to_check = NULL;
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FT_Int num_neighbour = 0;
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if ( y == 7 && x == 20 )
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to_check = NULL;
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if ( *s == 0 )
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goto Done;
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if ( *s > 0 && *s < 255 )
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{
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is_edge = 1;
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goto Done;
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}
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/* up */
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CHECK_NEIGHBOR( 0, -1 );
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@ -166,6 +170,122 @@
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#undef CHECK_NEIGHBOR
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/**************************************************************************
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*
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* @Function:
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* compute_gradient
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*
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* @Description:
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* [TODO]
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*
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* @Input:
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* [TODO]
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*
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* @Return:
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* [TODO]
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*/
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static FT_16D16_Vec
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compute_gradient( ED* current,
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FT_Int x,
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FT_Int y,
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FT_Int w,
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FT_Int r )
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{
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/* [TODO]: Write proper explanation. */
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FT_16D16_Vec g = { 0, 0 };
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if ( x <= 0 || x >= w - 1 ||
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y <= 0 || y >= r - 1 )
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return g;
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g.x = - current[-w - 1].dist -
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2 * current[ -1 ].dist -
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current[ w - 1].dist +
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current[-w + 1].dist +
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2 * current[ 1 ].dist +
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current[ w + 1].dist;
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g.y = - current[-w - 1].dist -
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2 * current[ -w ].dist -
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current[-w + 1].dist +
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current[ w - 1].dist +
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2 * current[ w ].dist +
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current[ w + 1].dist;
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FT_Vector_NormLen( &g );
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g.x = FT_MulFix( g.x, ONE / 2 - current->dist );
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g.y = FT_MulFix( g.y, ONE / 2 - current->dist );
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return g;
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}
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/**************************************************************************
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*
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* @Function:
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* bsdf_approximate_edge
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*
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* @Description:
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* [TODO]
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*
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* @Input:
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* [TODO]
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*
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* @Return:
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* [TODO]
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*/
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static FT_Error
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bsdf_approximate_edge( BSDF_Worker* worker )
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{
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/* [TODO]: Write proper explanation. */
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FT_Error error = FT_Err_Ok;
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FT_Int i, j;
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FT_Int index;
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ED* ed;
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if ( !worker || !worker->distance_map )
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{
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error = FT_THROW( Invalid_Argument );
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goto Exit;
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}
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ed = worker->distance_map;
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for ( j = 0; j < worker->rows; j++ )
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{
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for ( i = 0; i < worker->width; i++ )
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{
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index = j * worker->width + i;
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if ( ed[index].dist != 0 )
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ed[index].near = compute_gradient( ed + index, i, j,
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worker->width, worker->rows );
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}
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}
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for ( j = 0; j < worker->rows; j++ )
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{
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for ( i = 0; i < worker->width; i++ )
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{
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index = j * worker->width + i;
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if ( ed[index].dist == 0 )
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{
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ed[index].dist = 200 * ONE;
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ed[index].near.x = 100 * ONE;
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ed[index].near.y = 100 * ONE;
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}
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else
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ed[index].dist = FT_Vector_Length( &ed[index].near );
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}
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}
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Exit:
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return error;
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}
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/**************************************************************************
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*
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* @Function:
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@ -277,7 +397,7 @@
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{
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FT_Int t_index = t_j * t_width + t_i;
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FT_Int s_index;
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FT_Byte pixel_value;
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FT_Int pixel_value;
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t[t_index] = zero_ed;
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@ -290,10 +410,7 @@
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if ( s_i < 0 || s_i >= s_width ||
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s_j < 0 || s_j >= s_rows )
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{
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t[t_index].near.x = FT_INT_MAX;
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t[t_index].near.y = FT_INT_MAX;
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t[t_index].dist = 128 * ONE;
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t[t_index].sign = -1;
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t[t_index].sign = -1;
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continue;
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}
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@ -302,20 +419,19 @@
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else
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s_index = s_j * s_width + s_i;
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pixel_value = s[s_index];
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pixel_value = (FT_Int)s[s_index];
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/* clamp the pixel value to [0, 256] */
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if ( pixel_value == 255 )
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pixel_value = 256;
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/* only assign values to the edge pixels */
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if ( bsdf_is_edge( s + s_index , s_i, s_j, s_width, s_rows ) )
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{
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t[t_index].dist = 0;
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}
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else
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{
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t[t_index].near.x = FT_INT_MAX;
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t[t_index].near.y = FT_INT_MAX;
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t[t_index].dist = 128 * ONE;
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}
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t[t_index].dist = 256 * pixel_value;
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if ( pixel_value )
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/* We assume that if the pixel is inside a contour */
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/* then it's coverage value must be > 127. */
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if ( pixel_value > 127 )
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t[t_index].sign = 1;
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else
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t[t_index].sign = -1;
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worker.params = *sdf_params;
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FT_CALL( bsdf_init_distance_map( source, &worker ) );
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FT_CALL( bsdf_approximate_edge( &worker ) );
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FT_CALL( edt8( &worker ) );
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FT_CALL( finalize_sdf( &worker, target ) );
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