From 986d3108ac9fd0d7344bc83b20ccd64d433a02b3 Mon Sep 17 00:00:00 2001 From: Anuj Verma Date: Wed, 19 Aug 2020 12:56:58 +0530 Subject: [PATCH] [sdf] Add function to generate SDF. * src/sdf/ftsdf.c (sdf_generate): New function, currently disabled. This is a proof-of-concept implementation: It doesn't use any optimization, it simply checks all grid points against all contours. --- ChangeLog | 8 +++ src/sdf/ftsdf.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/ChangeLog b/ChangeLog index bfe6afc30..e5cb76d84 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2020-08-19 Anuj Verma + + [sdf] Add function to generate SDF. + + * src/sdf/ftsdf.c (sdf_generate): New function, currently disabled. + This is a proof-of-concept implementation: It doesn't use any + optimization, it simply checks all grid points against all contours. + 2020-08-19 Anuj Verma [sdf] Add functions to get shortest distance from any edge/contour. diff --git a/src/sdf/ftsdf.c b/src/sdf/ftsdf.c index 5a83d8fef..c17daff83 100644 --- a/src/sdf/ftsdf.c +++ b/src/sdf/ftsdf.c @@ -2887,6 +2887,166 @@ return error; } -#endif + + /************************************************************************** + * + * @Function: + * sdf_generate + * + * @Description: + * This is the main function that is responsible for generating signed + * distance fields. The function does not align or compute the size of + * `bitmap`; therefore the calling application must set up `bitmap` + * properly and transform the `shape' appropriately in advance. + * + * Currently we check all pixels against all contours and all edges. + * + * @Input: + * internal_params :: + * Internal parameters and properties required by the rasterizer. See + * @SDF_Params for more. + * + * shape :: + * A complete shape which is used to generate SDF. + * + * spread :: + * Maximum distances to be allowed in the output bitmap. + * + * @Output: + * bitmap :: + * The output bitmap which will contain the SDF information. + * + * @Return: + * FreeType error, 0 means success. + * + */ + static FT_Error + sdf_generate( const SDF_Params internal_params, + const SDF_Shape* shape, + FT_UInt spread, + const FT_Bitmap* bitmap ) + { + FT_Error error = FT_Err_Ok; + + FT_UInt width = 0; + FT_UInt rows = 0; + FT_UInt x = 0; /* used to loop in x direction, i.e., width */ + FT_UInt y = 0; /* used to loop in y direction, i.e., rows */ + FT_UInt sp_sq = 0; /* `spread` [* `spread`] as a 16.16 fixed value */ + + FT_Short* buffer; + + + if ( !shape || !bitmap ) + { + error = FT_THROW( Invalid_Argument ); + goto Exit; + } + + if ( spread < MIN_SPREAD || spread > MAX_SPREAD ) + { + error = FT_THROW( Invalid_Argument ); + goto Exit; + } + + width = bitmap->width; + rows = bitmap->rows; + buffer = (FT_Short*)bitmap->buffer; + + if ( USE_SQUARED_DISTANCES ) + sp_sq = FT_INT_16D16( spread * spread ); + else + sp_sq = FT_INT_16D16( spread ); + + if ( width == 0 || rows == 0 ) + { + FT_TRACE0(( "sdf_generate:" + " Cannot render glyph with width/height == 0\n" )); + FT_TRACE0(( " " + " (width, height provided [%d, %d])\n", + width, rows )); + + error = FT_THROW( Cannot_Render_Glyph ); + goto Exit; + } + + /* loop over all rows */ + for ( y = 0; y < rows; y++ ) + { + /* loop over all pixels of a row */ + for ( x = 0; x < width; x++ ) + { + /* `grid_point` is the current pixel position; */ + /* our task is to find the shortest distance */ + /* from this point to the entire shape. */ + FT_26D6_Vec grid_point = zero_vector; + SDF_Signed_Distance min_dist = max_sdf; + SDF_Contour* contour_list; + + FT_UInt index; + FT_Short value; + + + grid_point.x = FT_INT_26D6( x ); + grid_point.y = FT_INT_26D6( y ); + + /* This `grid_point' is at the corner, but we */ + /* use the center of the pixel. */ + grid_point.x += FT_INT_26D6( 1 ) / 2; + grid_point.y += FT_INT_26D6( 1 ) / 2; + + contour_list = shape->contours; + + /* iterate over all contours manually */ + while ( contour_list ) + { + SDF_Signed_Distance current_dist = max_sdf; + + + FT_CALL( sdf_contour_get_min_distance( contour_list, + grid_point, + ¤t_dist ) ); + + if ( current_dist.distance < min_dist.distance ) + min_dist = current_dist; + + contour_list = contour_list->next; + } + + /* [OPTIMIZATION]: if (min_dist > sp_sq) then simply clamp */ + /* the value to spread to avoid square_root */ + + /* clamp the values to spread */ + if ( min_dist.distance > sp_sq ) + min_dist.distance = sp_sq; + + /* square_root the values and fit in a 6.10 fixed point */ + if ( USE_SQUARED_DISTANCES ) + min_dist.distance = square_root( min_dist.distance ); + + if ( internal_params.orientation == FT_ORIENTATION_FILL_LEFT ) + min_dist.sign = -min_dist.sign; + if ( internal_params.flip_sign ) + min_dist.sign = -min_dist.sign; + + min_dist.distance /= 64; /* convert from 16.16 to 22.10 */ + + value = min_dist.distance & 0x0000FFFF; /* truncate to 6.10 */ + value *= min_dist.sign; + + if ( internal_params.flip_y ) + index = y * width + x; + else + index = ( rows - y - 1 ) * width + x; + + buffer[index] = value; + } + } + + Exit: + return error; + } + +#endif /* 0 */ /* END */