diff options
| -rw-r--r-- | src/sdf/ftsdf.c | 42 | ||||
| -rw-r--r-- | src/sdf/ftsdfcommon.h | 3 |
2 files changed, 39 insertions, 6 deletions
diff --git a/src/sdf/ftsdf.c b/src/sdf/ftsdf.c index 784e24705..0f9dffecf 100644 --- a/src/sdf/ftsdf.c +++ b/src/sdf/ftsdf.c @@ -1137,9 +1137,10 @@ 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 ) @@ -1148,12 +1149,25 @@ 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 benifit by */ + /* splitting it further, so we can just stop splitting. Here, */ + /* we check the deviation of the bezier and stop if it is */ + /* lower than a pre-defined `threhold` 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 +1264,31 @@ /* 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; + + /* Here we calculate the number of necessary bisections. Each */ + /* bisection reduces the deviation by exactly 4-fold, hence */ + /* we bisect the bezier until the deviation becomes less than */ + /* 1/8th of a pixel. For more details check `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; diff --git a/src/sdf/ftsdfcommon.h b/src/sdf/ftsdfcommon.h index 44f6bba53..a64774507 100644 --- a/src/sdf/ftsdfcommon.h +++ b/src/sdf/ftsdfcommon.h @@ -48,7 +48,8 @@ FT_BEGIN_HEADER #define MIN_SPREAD 2 /* maximum spread supported by the renderer */ #define MAX_SPREAD 32 - + /* pixel size in 26.6 */ +#define ONE_PIXEL ( 1 << 6 ) /************************************************************************** * |