diff options
Diffstat (limited to 'src/sdf/ftsdf.c')
| -rw-r--r-- | src/sdf/ftsdf.c | 52 |
1 files changed, 43 insertions, 9 deletions
diff --git a/src/sdf/ftsdf.c b/src/sdf/ftsdf.c index f5e5551e6..fa551ea6e 100644 --- a/src/sdf/ftsdf.c +++ b/src/sdf/ftsdf.c @@ -764,9 +764,9 @@ const FT_26D6_Vec* to, void* user ) { - SDF_Shape* shape = ( SDF_Shape* )user; - SDF_Edge* edge = NULL; - SDF_Contour* contour = NULL; + SDF_Shape* shape = ( SDF_Shape* )user; + SDF_Edge* edge = NULL; + SDF_Contour* contour = NULL; FT_Error error = FT_Err_Ok; FT_Memory memory = shape->memory; @@ -1137,23 +1137,38 @@ FT_Int max_splits, SDF_Edge** out ) { - FT_Error error = FT_Err_Ok; - FT_26D6_Vec cpos[7]; - SDF_Edge* left,* right; + FT_Error error = FT_Err_Ok; + FT_26D6_Vec cpos[7]; + SDF_Edge* left, *right; + const FT_26D6 threshold = ONE_PIXEL / 4; - if ( !memory || !out ) + if ( !memory || !out ) { error = FT_THROW( Invalid_Argument ); goto Exit; } - /* split the conic */ + /* split the cubic */ cpos[0] = control_points[0]; cpos[1] = control_points[1]; cpos[2] = control_points[2]; cpos[3] = control_points[3]; + /* If the segment is flat enough we won't get any benefit by */ + /* splitting it further, so we can just stop splitting. */ + /* */ + /* Check the deviation of the Bezier curve and stop if it is */ + /* smaller than the pre-defined `threshold` value. */ + if ( FT_ABS( 2 * cpos[0].x - 3 * cpos[1].x + cpos[3].x ) < threshold && + FT_ABS( 2 * cpos[0].y - 3 * cpos[1].y + cpos[3].y ) < threshold && + FT_ABS( cpos[0].x - 3 * cpos[2].x + 2 * cpos[3].x ) < threshold && + FT_ABS( cpos[0].y - 3 * cpos[2].y + 2 * cpos[3].y ) < threshold ) + { + split_cubic( cpos ); + goto Append; + } + split_cubic( cpos ); /* If max number of splits is done */ @@ -1250,13 +1265,32 @@ /* Subdivide the curve and add it to the list. */ { FT_26D6_Vec ctrls[3]; + FT_26D6 dx, dy; + FT_UInt num_splits; ctrls[0] = edge->start_pos; ctrls[1] = edge->control_a; ctrls[2] = edge->end_pos; - error = split_sdf_conic( memory, ctrls, 32, &new_edges ); + dx = FT_ABS( ctrls[2].x + ctrls[0].x - 2 * ctrls[1].x ); + dy = FT_ABS( ctrls[2].y + ctrls[0].y - 2 * ctrls[1].y ); + if ( dx < dy ) + dx = dy; + + /* Calculate the number of necessary bisections. Each */ + /* bisection causes a four-fold reduction of the deviation, */ + /* hence we bisect the Bezier curve until the deviation */ + /* becomes less than 1/8th of a pixel. For more details */ + /* check file `ftgrays.c`. */ + num_splits = 1; + while ( dx > ONE_PIXEL / 8 ) + { + dx >>= 2; + num_splits <<= 1; + } + + error = split_sdf_conic( memory, ctrls, num_splits, &new_edges ); } break; |