September 2017 Update

Task/Hough-transform/Zkl/hough-transform-1.zkl

@@ -0,0 +1,17 @@
+const WHITE=0xffFFff, X=0x010101;
+fcn houghTransform(image,hx=460,hy=360){
+   if(hy.isOdd) hy-=1; // hy argument must be even
+   out:=PPM(hx,hy,WHITE);
+   rMax:=image.w.toFloat().hypot(image.h);
+   dr,dTh:=rMax/(hy/2), (0.0).pi/hx;
+
+   foreach y,x in (image.h,image.w){
+      if(image[x,y]==WHITE) continue;
+      foreach iTh in (hx){
+         th,r:=dTh*iTh, th.cos()*x + th.sin()*y;
+	 iry:=hy/2 + (r/dr + 0.5).floor();  // y==0 is top
+	 if(out[iTh,iry]>0) out[iTh,iry]=out[iTh,iry] - X;
+      }
+   }
+   out
+}

Task/Hough-transform/Zkl/hough-transform-2.zkl

@@ -0,0 +1,8 @@
+fcn readPNG2PPM(fileName){
+   p:=System.popen("convert \"%s\" ppm:-".fmt(fileName),"r");
+      img:=PPM.readPPM(p);
+   p.close();
+   img
+}
+houghTransform(readPNG2PPM("pentagon.png"))
+.write(File("pentagon_hough.ppm","wb"));