[Pen-commits] SF.net SVN: pen:[117] src/maskutils.c

[<mdg...@us...>]

Revision: 117
          http://pen.svn.sourceforge.net/pen/?rev=117&view=rev
Author:   mdgeorge
Date:     2008-12-03 23:44:26 +0000 (Wed, 03 Dec 2008)

Log Message:
-----------
Added in bitmask_convolve and bitmask_find_closest from history.

Modified Paths:
--------------
    src/maskutils.c

Modified: src/maskutils.c
===================================================================
--- src/maskutils.c	2008-12-03 23:43:41 UTC (rev 116)
+++ src/maskutils.c	2008-12-03 23:44:26 UTC (rev 117)
@@ -1,6 +1,10 @@
 #include <Python.h>
 #include <mask.h>
 
+/*
+** Declarations and python magic ***********************************************
+*/
+
 static const char DOC_CONVOLVE[] =
 "Return the convolution of self with another mask.                             \n"
 "                                                                              \n"
@@ -31,16 +35,80 @@
 };
 
 void
-initmaskutils()
+initmaskutils(void)
 {
-	PyInitModule ("maskutils", maskutils_methods);
+	Py_InitModule ("maskutils", maskutils_methods);
 }
 
 /*
-** Implementations *************************************************************
+** Python method implementations ***********************************************
 */
 
 static
+void
+bitmask_convolve(const bitmask_t *a, const bitmask_t *b, bitmask_t *o, int xoffset, int yoffset)
+{
+  int x, y;
+
+  xoffset += b->w - 1;
+  yoffset += b->h - 1;
+  for (y = 0; y < b->h; y++)
+	for (x = 0; x < b->w; x++)
+	  if (bitmask_getbit(b, x, y))
+		bitmask_draw(o, a, xoffset - x, yoffset - y);
+}
+
+static inline
+int
+valid(const bitmask_t *mask, int x, int y)
+{
+  return x < 0        || y < 0        ||
+		 x >= mask->w || y >= mask->h ||
+		 !bitmask_getbit(mask,x,y);
+}
+
+static
+void
+bitmask_find_closest(const bitmask_t *mask, int *x, int *y)
+{
+#define SQ(x) (x)*(x)
+
+  /* this method is either very elegant or very ugly. */
+  int best_d = SQ(*x + 1), best_x = -1, best_y = *y;
+  int covered;
+
+#define check_point(dist,x,y) \
+  if(dist < best_d) {      \
+	best_d = dist;         \
+	best_x = x;            \
+	best_y = y;            \
+  }
+
+  if (valid(mask, *x, *y))
+	check_point(0, *x, *y);
+
+  /* loop invariant: I've at least looked at everything of distance less than less than covered */
+  for (covered = 1; SQ(covered) <= best_d; covered++)
+  {
+	int sx, sy, i;
+
+#define check_row(xi, yi)                               \
+	sx = *x - (xi)*covered + (yi)*covered;               \
+	sy = *y - (yi)*covered - (xi)*covered;               \
+	for (i = 0; i < 2*covered; i++, sx += xi, sy += yi) \
+	  if (valid(mask, sx, sy))                          \
+	check_point(SQ(*x-sx) + SQ(*y-sy), sx, sy);
+
+	check_row(1,0);
+	check_row(-1,0);
+	check_row(0,1);
+	check_row(0,-1);
+  }
+
+  *x = best_x; *y = best_y;
+}
+
+static
 PyObject *
 maskutils_convolve(PyObject *self /* Not used */, PyObject *args)
 {


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