Question

I have a problem with coloring the Mandelbrot set.
This is my onDraw() procedure:

@Override
protected void onDraw(Canvas canvas) {
   g = Math.round(60+(iter_count*(2500/16)));
   iter_count++;
   for(int xx = 1; xx <= xMax; xx++) {
       for(int yy = 1; yy <= yMax; yy++) {
           schirmzupap(ar,br,bi,ai,xx,yy,xMax,yMax);
           n = 1;
           zr0 = zr;
           zi0 = zi;
           while ((n<g) && (zr*zr+zi*zi<4)) {
               zrh = zr;
               zr = (zr*zr)-zi*zi+zr0;
               zi = zrh*zi+zi*zrh+zi0;
               n++;
           }
           if (n==g) {                                                //[Coloring]
               paint.setARGB(255,0,0,0);  
           }
           if ((n/g) < (1/2)) {
               paint.setARGB(255,Math.round((n/g)*255),0,0);
           }
           if (((n/g) < 1) && ((n/g) > 1/2)) {
               paint.setARGB(255,255,Math.round((n/g)*255),Math.round((n/g)*255));  
           }
           canvas.drawPoint(xx, yy, paint);                           //[/Coloring]
       }              
    }
}

This is how it looks at the Java Android emulator: http://i55.tinypic.com/14ctqi8.png

This is how I want it to look: http://i54.tinypic.com/nh1aqe.png It’s written in Delphi, but the coloring part is actually the same:

if n=g then image1.canvas.Pixels[xx,yy]:=RGB2TColor(0,0,0);
if (n/g)<(1/2) then image1.canvas.Pixels[xx,yy]:=RGB2TColor(Round((n/g)*255),0,0);
if ((n/g)<(1)) AND ((n/g)>(1/2)) then image1.canvas.Pixels[xx,yy]:=RGB2TColor(255,Round((n/g)*255),Round((n/g)*255));

Could someone help me please?
Greetz,

Henry

Answer 1

As Sanjay said your have a problem with division.

if ((n/g) < (1/2)) {...

if (((n/g) < 1) && ((n/g) > 1/2)) {....

You could fix in Sanjay-way. But take attention 1/2=0 1.0/2=0.5.
Or less readeble but a bit faster

if((2*n)<g){...

and

if((n<g)&&(2*n>g)){...