<?php
/* (C) 2011.1 by Julian von Mendel (prog@derjulian.net) */

require_once("image.php");

class circleFinder {
    protected $img;
    protected $pixel;
    protected $color;
    
    /* required during pixel count */
    protected $matches = 0;
    protected $pixelcount = 0;

    function __construct($img, $channel = image::black) {
        /* note that channel == image::all makes no sense, as we need the
           intensity on a single color channel */
        $this->img = $img;
        $img->initpixelcache();
        $this->pixel = $img->pixel($channel);
        $this->color = $img->colorallocate(255, 0, 0);
    }

    public function find() {
        $best = 0;
        $img = $this->img;
                
        //for ($r = (min($img->width(), $img->height()) / 2); $r > 10; $r--) {
        for ($r = 29; $r >= 23; $r--) {
echo "r".$r."\n"; // TODO: debug code
            for ($x = $r; $x < $img->width() - $r; $x++) {
                for ($y = $r; $y < $img->height() - $r; $y++) {
                    if (($fit = $this->checkPossibility($x, $y, $r)) &&
                            $fit > $best) {
                        $best = $fit;
                        $bx = $x; $by = $y; $br = $r;
echo "match ".round($fit)."%: x $x y $y r $r\n"; // TODO: debug code
                    }
                }
            }
        }

echo "result ".round($best)."%: x $bx y $by r $br\n"; // TODO: debug code
        $img->ellipse($bx, $by, 2*$br, 2*$br, $this->color);
        return $img;
    }

    protected function checkPossibility($xCenter, $yCenter, $r) {
        $this->matches = 0;
        $this->pixelcount = 0;
        $this->circleMidPoint($xCenter, $yCenter, $r);
        
        return ($this->matches / $this->pixelcount / 2.55);
    }
    
    private function match($x, $y) {
        //if($x < 0 || $y < 0 || $x >= $this->img->width() || $y >= $this->img->height())
        //    return;
        
        $intensity = reset($this->pixel[$x][$y]);
        $this->pixelcount++;
        $this->matches += $intensity;
    }
   
    /* adopted from and explained at
       http://www.cs.unc.edu/~mcmillan/comp136/Lecture7/circle.html */
    private function circlePoints($cx, $cy, $x, $y) {
        if ($x == 0) {
            $this->match($cx, $cy + $y);
            $this->match($cx, $cy - $y);
            $this->match($cx + $y, $cy);
            $this->match($cx - $y, $cy);
        } else if ($x == $y) {
            $this->match($cx + $x, $cy + $y);
            $this->match($cx - $x, $cy + $y);
            $this->match($cx + $x, $cy - $y);
            $this->match($cx - $x, $cy - $y);
        } else if ($x < $y) {
            $this->match($cx + $x, $cy + $y);
            $this->match($cx - $x, $cy + $y);
            $this->match($cx + $x, $cy - $y);
            $this->match($cx - $x, $cy - $y);
            $this->match($cx + $y, $cy + $x);
            $this->match($cx - $y, $cy + $x);
            $this->match($cx + $y, $cy - $x);
            $this->match($cx - $y, $cy - $x);
        }
    }

    protected function circleMidpoint($xCenter, $yCenter, $r) {
        $x = 0;
        $y = $r;
        $p = (5 - $r*4) / 4;

        $this->circlePoints($xCenter, $yCenter, $x, $y);
        while ($x < $y) {
            $x++;
            if ($p < 0) {
                $p += 2*$x+1;
            } else {
                $y--;
                $p += 2*($x-$y)+1;
            }
            $this->circlePoints($xCenter, $yCenter, $x, $y);
        }
    }
}