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+implement Buildstrokes;
+
+#
+# this Limbo code is derived from C code that had the following
+# copyright notice, which i reproduce as requested
+#
+# li_strokesnizer.c
+#
+# Copyright 2000 Compaq Computer Corporation.
+# Copying or modifying this code for any purpose is permitted,
+# provided that this copyright notice is preserved in its entirety
+# in all copies or modifications.
+# COMPAQ COMPUTER CORPORATION MAKES NO WARRANTIES, EXPRESSED OR
+# IMPLIED, AS TO THE USEFULNESS OR CORRECTNESS OF THIS CODE OR
+#
+#
+# Adapted from cmu_strokesnizer.c by Jay Kistler.
+#
+# Where is the CMU copyright???? Gotta track it down - Jim Gettys
+#
+# Credit to Dean Rubine, Jim Kempf, and Ari Rapkin.
+#
+
+include "sys.m";
+ sys: Sys;
+
+include "strokes.m";
+ strokes: Strokes;
+ Classifier, Penpoint, Stroke, Region: import strokes;
+ Rconvex, Rconcave, Rplain, Rpseudo: import Strokes;
+
+lidebug: con 0;
+stderr: ref Sys->FD;
+
+init(r: Strokes)
+{
+ sys = load Sys Sys->PATH;
+ if(lidebug)
+ stderr = sys->fildes(2);
+ strokes = r;
+}
+
+#
+# Implementation of the Li/Yeung recognition algorithm
+#
+
+# Pre-processing and canonicalization parameters
+CANONICAL_X: con 108;
+CANONICAL_Y: con 128;
+NCANONICAL: con 50;
+
+
+#
+# calculate canonical forms
+#
+
+canonical_example(nclasses: int, cnames: array of string, examples: array of list of ref Stroke): (string, array of ref Stroke, array of ref Stroke)
+{
+ canonex := array[nclasses] of ref Stroke;
+ dompts := array[nclasses] of ref Stroke;
+
+ # make canonical examples for each class.
+ for(i := 0; i < nclasses; i++){
+ if(lidebug)
+ sys->fprint(stderr, "canonical_example: class %s\n", cnames[i]);
+
+ # Make a copy of the examples.
+ pts: list of ref Stroke = nil;
+ nex := 0;
+ for(exl := examples[i]; exl != nil; exl = tl exl){
+ t := hd exl;
+ pts = t.copy() :: pts;
+ nex++;
+ }
+
+ # Canonicalize each example, and derive the max x and y ranges.
+ maxxrange := 0;
+ maxyrange := 0;
+ for(exl = pts; exl != nil; exl = tl exl){
+ e := hd exl;
+ ce := canonical_stroke(e);
+ if(ce == nil){
+ if(lidebug)
+ sys->fprint(stderr, "example discarded: can't make canonical form\n");
+ continue; # try the next one
+ }
+ *e = *ce;
+ if(e.xrange > maxxrange)
+ maxxrange = e.xrange;
+ if(e.yrange > maxyrange)
+ maxyrange = e.yrange;
+ }
+
+ # Normalise max ranges.
+ (maxxrange, maxyrange) = normalise(maxxrange, maxyrange, CANONICAL_X, CANONICAL_Y);
+
+ # Re-scale each example to max ranges.
+ for(exl = pts; exl != nil; exl = tl exl){
+ t := hd exl;
+ scalex, scaley: int;
+ if(t.xrange == 0)
+ scalex = 100;
+ else
+ scalex = (100*maxxrange + t.xrange/2) / t.xrange;
+ if(t.yrange == 0)
+ scaley = 100;
+ else
+ scaley = (100*maxyrange + t.yrange/2) / t.yrange;
+ t.translate(0, 0, scalex, scaley);
+ }
+
+ # Average the examples; leave average in first example.
+ avg := hd pts; # careful, aliasing
+ for(k := 0; k < NCANONICAL; k++){
+ xsum := 0;
+ ysum := 0;
+ for(exl = pts; exl != nil; exl = tl exl){
+ t := hd exl;
+ xsum += t.pts[k].x;
+ ysum += t.pts[k].y;
+ }
+ avg.pts[k].x = (xsum + nex/2) / nex;
+ avg.pts[k].y = (ysum + nex/2) / nex;
+ }
+
+ # rescale averaged stroke
+ avg.scaleup();
+
+ # Re-compute the x and y ranges and center the stroke.
+ avg.center();
+
+ canonex[i] = avg; # now it's the canonical representation
+
+ if(lidebug){
+ sys->fprint(stderr, "%s, avgpts = %d\n", cnames[i], avg.npts);
+ for(j := 0; j < avg.npts; j++){
+ p := avg.pts[j];
+ sys->fprint(stderr, " (%d %d)\n", p.x, p.y);
+ }
+ }
+
+ dompts[i] = avg.interpolate().dominant(); # dominant points of canonical representation
+ }
+
+ return (nil, canonex, dompts);
+}
+
+normalise(x, y: int, xrange, yrange: int): (int, int)
+{
+ if((100*x + xrange/2)/xrange > (100*y + yrange/2)/yrange){
+ y = (y*xrange + x/2)/x;
+ x = xrange;
+ }else{
+ x = (x*yrange + y/2)/y;
+ y = yrange;
+ }
+ return (x, y);
+}
+
+canonical_stroke(points: ref Stroke): ref Stroke
+{
+ points = points.filter();
+ if(points.npts < 2)
+ return nil;
+
+ # Scale up to avoid conversion errors.
+ points.scaleup();
+
+ # Compute an equivalent stroke with equi-distant points
+ points = compute_equipoints(points);
+ if(points == nil)
+ return nil;
+
+ # Re-translate the points to the origin.
+ (minx, miny, maxx, maxy) := points.bbox();
+ points.translate(minx, miny, 100, 100);
+
+ # Store the x and y ranges in the point list.
+ points.xrange = maxx - minx;
+ points.yrange = maxy - miny;
+
+ if(lidebug){
+ sys->fprint(stderr, "Canonical stroke: %d, %d, %d, %d\n", minx, miny, maxx, maxy);
+ for(i := 0; i < points.npts; i++){
+ p := points.pts[i];
+ sys->fprint(stderr, " (%d %d)\n", p.x, p.y);
+ }
+ }
+
+ return points;
+}
+
+compute_equipoints(points: ref Stroke): ref Stroke
+{
+ pathlen := points.length();
+ equidist := (pathlen + (NCANONICAL-1)/2) / (NCANONICAL-1);
+ equipoints := array[NCANONICAL] of Penpoint;
+ if(lidebug)
+ sys->fprint(stderr, "compute_equipoints: npts = %d, pathlen = %d, equidist = %d\n",
+ points.npts, pathlen, equidist);
+
+ # First original point is an equipoint.
+ equipoints[0] = points.pts[0];
+ nequipoints := 1;
+ dist_since_last_eqpt := 0;
+
+ for(i := 1; i < points.npts; i++){
+ dx1 := points.pts[i].x - points.pts[i-1].x;
+ dy1 := points.pts[i].y - points.pts[i-1].y;
+ endx := points.pts[i-1].x*100;
+ endy := points.pts[i-1].y*100;
+ remaining_seglen := strokes->sqrt(100*100 * (dx1*dx1 + dy1*dy1));
+ dist_to_next_eqpt := equidist - dist_since_last_eqpt;
+ while(remaining_seglen >= dist_to_next_eqpt){
+ if(dx1 == 0){
+ # x-coordinate stays the same
+ if(dy1 >= 0)
+ endy += dist_to_next_eqpt;
+ else
+ endy -= dist_to_next_eqpt;
+ }else{
+ slope := (100*dy1 + dx1/2) / dx1;
+ tmp := strokes->sqrt(100*100 + slope*slope);
+ dx := (100*dist_to_next_eqpt + tmp/2) / tmp;
+ dy := (slope*dx + 50)/100;
+ if(dy < 0)
+ dy = -dy;
+ if(dx1 >= 0)
+ endx += dx;
+ else
+ endx -= dx;
+ if(dy1 >= 0)
+ endy += dy;
+ else
+ endy -= dy;
+ }
+ equipoints[nequipoints].x = (endx + 50) / 100;
+ equipoints[nequipoints].y = (endy + 50) / 100;
+ nequipoints++;
+ #assert(nequipoints <= NCANONICAL);
+ dist_since_last_eqpt = 0;
+ remaining_seglen -= dist_to_next_eqpt;
+ dist_to_next_eqpt = equidist;
+ }
+ dist_since_last_eqpt += remaining_seglen;
+ }
+
+ # Take care of last equipoint.
+ if(nequipoints == NCANONICAL-1){
+ # Make last original point the last equipoint.
+ equipoints[nequipoints++] = points.pts[points.npts - 1];
+ }
+ if(nequipoints != NCANONICAL){ # fell short
+ if(lidebug)
+ sys->fprint(stderr,"compute_equipoints: nequipoints = %d\n", nequipoints);
+ # assert(false);
+ return nil;
+ }
+ return ref Stroke(NCANONICAL, equipoints, 0, 0);
+}
generated by cgit v1.2.3 (git 2.46.0) at 2025-12-10 18:10:36 +0000