cleanup

git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@4677 9d0c8265-081b-0410-96cb-a4ca84ce46f8

1 files changed, 57 insertions, 0 deletions

diff --git a/converter/other/pamtosvg/curve.c b/converter/other/pamtosvg/curve.c
index 5c9c7157..d7fff87d 100644
--- a/converter/other/pamtosvg/curve.c
+++ b/converter/other/pamtosvg/curve.c
@@ -18,6 +18,8 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
+#include <assert.h>
+
 #include "mallocvar.h"
 
 #include "logreport.h"
@@ -133,6 +135,61 @@ curve_appendPixel(Curve *       const curveP,
 
 
 
+void
+curve_setDistance(Curve * const curveP) {
+/*----------------------------------------------------------------------------
+   Fill in the distance values in *curveP.
+
+   The distance value for point P on a curve is the distance P is along the
+   curve from the initial point, normalized so the entire curve is length 1.0
+   (i.e. t of the initial point is 0.0; t of the final point is 1.0).
+
+   There are a lot of curves that pass through the points indicated by
+   *curveP, but for practical computation of t, we just take the piecewise
+   linear locus that runs through all of them.  That means we can just step
+   through *curveP, adding up the distance from one point to the next to get
+   the t value for each point.
+
+   This is the "chord-length parameterization" method, which is described in
+   Plass & Stone.
+-----------------------------------------------------------------------------*/
+    unsigned int p;
+
+    LOG("\nAssigning initial t values:\n  ");
+
+    /* Algorithm: We do a pass through the curve establishing how far each
+       point is along the curve in absolute terms, and then another pass
+       to normalize those distances to the fraction of the curve (i.e.
+       if the curve is 5 units long and Point P is 2 units in, we record
+       2 units for Point P in the first pass, and then compute 0.2 as the
+       fraction of the curve length in the second pass.
+
+       In the first pass, we abuse the distance property of the CurvePoint
+       object to remember the unnormalized distances.
+    */
+
+    CURVE_DIST(curveP, 0) = 0.0;
+
+    for (p = 1; p < CURVE_LENGTH(curveP); ++p) {
+        Point const point      = CURVE_POINT(curveP, p);
+        Point const previous_p = CURVE_POINT(curveP, p - 1);
+        float const d          = point_distance(point, previous_p);
+        CURVE_DIST(curveP, p)  = CURVE_DIST(curveP, p - 1) + d;
+    }
+
+    assert(LAST_CURVE_DIST(curveP) != 0.0);
+
+    /* Normalize to a curve length of 1.0 */
+
+    for (p = 1; p < CURVE_LENGTH(curveP); ++p)
+        CURVE_DIST(curveP, p) =
+            CURVE_DIST(curveP, p) / LAST_CURVE_DIST(curveP);
+
+    curve_logEntire(curveP);
+}
+
+
+
 #define NUM_TO_PRINT 3
 
 #define LOG_CURVE_POINT(c, p, printDistance) \