[sdf] Add essential structures for the 'bsdf' rasterizer.

* src/sdf/ftbsdf.c (ONE): New macro.
(BSDF_TRaster, ED, BSDF_Worker): New structures.
(zero_ed): New constant.

ChangeLog

@@ -1,3 +1,11 @@
+2020-08-20  Anuj Verma  <anujv@iitbhilai.ac.in>
+
+	[sdf] Add essential structures for the 'bsdf' rasterizer.
+
+	* src/sdf/ftbsdf.c (ONE): New macro.
+	(BSDF_TRaster, ED, BSDF_Worker): New structures.
+	(zero_ed): New constant.
+
 2020-08-20  Anuj Verma  <anujv@iitbhilai.ac.in>
 
 	[sdf] Add 'sdf' module to non-gnumake build systems.

src/sdf/ftbsdf.c

@@ -1,3 +1,132 @@
 
+#include <freetype/internal/ftobjs.h>
+#include <freetype/internal/ftdebug.h>
+#include <freetype/internal/ftmemory.h>
+#include <freetype/fttrigon.h>
+
+#include "ftsdf.h"
+#include "ftsdferrs.h"
+#include "ftsdfcommon.h"
+
+
+  /**************************************************************************
+   *
+   * useful macros
+   *
+   */
+
+#define ONE  65536 /* 1 in 16.16 */
+
+
+  /**************************************************************************
+   *
+   * structs
+   *
+   */
+
+
+  /**************************************************************************
+   *
+   * @Struct:
+   *   BSDF_TRaster
+   *
+   * @Description:
+   *   This struct is used in place of @FT_Raster and is stored within the
+   *   internal FreeType renderer struct.  While rasterizing this is passed
+   *   to the @FT_Raster_RenderFunc function, which then can be used however
+   *   we want.
+   *
+   * @Fields:
+   *   memory ::
+   *     Used internally to allocate intermediate memory while raterizing.
+   *
+   */
+  typedef struct  BSDF_TRaster_
+  {
+    FT_Memory  memory;
+
+  } BSDF_TRaster;
+
+
+  /**************************************************************************
+   *
+   * @Struct:
+   *   ED
+   *
+   * @Description:
+   *   Euclidean distance.  It gets used for Euclidean distance transforms;
+   *   it can also be interpreted as an edge distance.
+   *
+   * @Fields:
+   *   dist ::
+   *     Vector length of the `near` parameter.  Can be squared or absolute
+   *     depending on the `USE_SQUARED_DISTANCES` macro defined in file
+   *     `ftsdfcommon.h`.
+   *
+   *   near ::
+   *     Vector to the nearest edge.  Can also be interpreted as shortest
+   *     distance of a point.
+   *
+   *   alpha ::
+   *     Alpha value of the original bitmap from which we generate SDF.
+   *     Needed for computing the gradient and determining the proper sign
+   *     of a pixel.
+   *
+   */
+  typedef struct  ED_
+  {
+    FT_16D16      dist;
+    FT_16D16_Vec  near;
+    FT_Byte       alpha;
+
+  } ED;
+
+
+  /**************************************************************************
+   *
+   * @Struct:
+   *   BSDF_Worker
+   *
+   * @Description:
+   *   A convenience struct that is passed to functions while generating
+   *   SDF; most of those functions require the same parameters.
+   *
+   * @Fields:
+   *   distance_map ::
+   *     A one-dimensional array that gets interpreted as two-dimensional
+   *     one.  It contains the Euclidean distances of all points of the
+   *     bitmap.
+   *
+   *   width ::
+   *     Width of the above `distance_map`.
+   *
+   *   rows ::
+   *     Number of rows in the above `distance_map`.
+   *
+   *   params ::
+   *     Internal parameters and properties required by the rasterizer.  See
+   *     file `ftsdf.h` for more.
+   *
+   */
+  typedef struct  BSDF_Worker_
+  {
+    ED*  distance_map;
+
+    FT_Int  width;
+    FT_Int  rows;
+
+    SDF_Raster_Params  params;
+
+  } BSDF_Worker;
+
+
+  /**************************************************************************
+   *
+   * initializer
+   *
+   */
+
+  static const ED  zero_ed = { 0, { 0, 0 }, 0 };
+
 
 /* END */