Commit c5761764614c1bb25d53adebe406161ee679628e
2020-08-20T09:20:26
[sdf] Add function to find edge pixels in a grid of alpha values. * src/sdf/ftbsdf.c (bsdf_is_edge): New function.
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diff --git a/ChangeLog b/ChangeLog
index 75f22aa..86a6308 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
2020-08-20 Anuj Verma <anujv@iitbhilai.ac.in>
+ [sdf] Add function to find edge pixels in a grid of alpha values.
+
+ * src/sdf/ftbsdf.c (bsdf_is_edge): New function.
+
+2020-08-20 Anuj Verma <anujv@iitbhilai.ac.in>
+
[sdf] Add essential structures for the 'bsdf' rasterizer.
* src/sdf/ftbsdf.c (ONE): New macro.
diff --git a/src/sdf/ftbsdf.c b/src/sdf/ftbsdf.c
index 07ad958..2229354 100644
--- a/src/sdf/ftbsdf.c
+++ b/src/sdf/ftbsdf.c
@@ -129,4 +129,115 @@
static const ED zero_ed = { 0, { 0, 0 }, 0 };
+ /**************************************************************************
+ *
+ * rasterizer functions
+ *
+ */
+
+ /**************************************************************************
+ *
+ * @Function:
+ * bsdf_is_edge
+ *
+ * @Description:
+ * Check whether a pixel is an edge pixel, i.e., whether it is
+ * surrounded by a completely black pixel (zero alpha), and the current
+ * pixel is not a completely black pixel.
+ *
+ * @Input:
+ * dm ::
+ * Array of distances. The parameter must point to the current
+ * pixel, i.e., the pixel that is to be checked for being an edge.
+ *
+ * x ::
+ * The x position of the current pixel.
+ *
+ * y ::
+ * The y position of the current pixel.
+ *
+ * w ::
+ * Width of the bitmap.
+ *
+ * r ::
+ * Number of rows in the bitmap.
+ *
+ * @Return:
+ * 1~if the current pixel is an edge pixel, 0~otherwise.
+ *
+ */
+
+#ifdef CHECK_NEIGHBOR
+#undef CHECK_NEIGHBOR
+#endif
+
+#define CHECK_NEIGHBOR( x_offset, y_offset ) \
+ if ( x + x_offset >= 0 && x + x_offset < w && \
+ y + y_offset >= 0 && y + y_offset < r ) \
+ { \
+ num_neighbors++; \
+ \
+ to_check = dm + y_offset * w + x_offset; \
+ if ( to_check->alpha == 0 ) \
+ { \
+ is_edge = 1; \
+ goto Done; \
+ } \
+ }
+
+ static FT_Bool
+ bsdf_is_edge( ED* dm, /* distance map */
+ FT_Int x, /* x index of point to check */
+ FT_Int y, /* y index of point to check */
+ FT_Int w, /* width */
+ FT_Int r ) /* rows */
+ {
+ FT_Bool is_edge = 0;
+ ED* to_check = NULL;
+ FT_Int num_neighbors = 0;
+
+
+ if ( dm->alpha == 0 )
+ goto Done;
+
+ if ( dm->alpha > 0 && dm->alpha < 255 )
+ {
+ is_edge = 1;
+ goto Done;
+ }
+
+ /* up */
+ CHECK_NEIGHBOR( 0, -1 );
+
+ /* down */
+ CHECK_NEIGHBOR( 0, 1 );
+
+ /* left */
+ CHECK_NEIGHBOR( -1, 0 );
+
+ /* right */
+ CHECK_NEIGHBOR( 1, 0 );
+
+ /* up left */
+ CHECK_NEIGHBOR( -1, -1 );
+
+ /* up right */
+ CHECK_NEIGHBOR( 1, -1 );
+
+ /* down left */
+ CHECK_NEIGHBOR( -1, 1 );
+
+ /* down right */
+ CHECK_NEIGHBOR( 1, 1 );
+
+ if ( num_neighbors != 8 )
+ is_edge = 1;
+
+ Done:
+ return is_edge;
+ }
+
+#undef CHECK_NEIGHBOR
+
+
/* END */