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#### Should detect few circles in an image, detects WAY MORE!

Im using the symmetry property in the isCenterofCircle():check at a distance +r and -r away from the pixel(center)
(vertical and horizontal direction) to see if those 4 pixels are different than the center one. If yes, highlight in red.

However, it creates way more circles even if it's just empty space.

Code:
```
public class ***1 {

public static void main(String[] args) {
try {
// arg 0 is the input image name

// arg 1 is the min radius
int minr = Integer.parseInt(args[1]);

// arg 2 is the max radius
int maxr = Integer.parseInt(args[2]);

// if present, arg 3 is the max width we consider
int w = (args.length>3) ? Integer.parseInt(args[3]) : img.getWidth();

// if present, arg 4 is the max height we consider
int h = (args.length>4) ? Integer.parseInt(args[4]) : img.getHeight();

findCircle(minr, img, w, h);

//   System.out.println("Coordinates: (" + row + "," + column + ")\n Radius: " + minr);
//----
// write out the image
File outputfile = new File("outputimage2.png");
ImageIO.write(img, "png", outputfile);
} catch (Exception e) {
e.printStackTrace();
}
}

// Bresenham's algorithm to draw a circle
// requires circle center and radius, as well as the
// image and Graphics2D object with drawing colour already set.
static void drawCircle(int cx,int cy,int r,Graphics2D g) {
int f = 1-r;
int ddF_x = 1;
int ddF_y = -2 * r;
int x = 0;
int y = r;

// draw cardinal points
g.drawLine(cx,cy+r,cx,cy+r);
g.drawLine(cx,cy-r,cx,cy-r);
g.drawLine(cx+r,cy,cx+r,cy);
g.drawLine(cx-r,cy,cx-r,cy);

// draw 1/8 of the circle, taking advantage of symmetry
while(x < y) {
if(f >= 0) {
y--;
ddF_y += 2;
f += ddF_y;
}
x++;
ddF_x += 2;
f += ddF_x;

g.drawLine(cx+x,cy+y,cx+x,cy+y);
g.drawLine(cx-x,cy+y,cx-x,cy+y);
g.drawLine(cx+x,cy-y,cx+x,cy-y);
g.drawLine(cx-x,cy-y,cx-x,cy-y);
g.drawLine(cx+y,cy+x,cx+y,cy+x);
g.drawLine(cx-y,cy+x,cx-y,cy+x);
g.drawLine(cx+y,cy-x,cx+y,cy-x);
g.drawLine(cx-y,cy-x,cx-y,cy-x);
}

}

/**
* I think that this method can just be called to get each pixel rather than copying all of the pixels into an
* array.
*
* @param col The column of the pixel to get.  If this isn't a valid pixel, then null is returned.
* @param row The rowof the pixel to get.  If this isn't a valid pixel, then null is returned.
* @param image The image to get the pixel from.
* @return Returns the pixel specified by col and row.  If anything is wrong, then null is returned.
*/
static Integer getPixel(int row, int col, BufferedImage image) {
// check the indexes and return null for bad index or return a pixel for good index values
if (image == null) {
return null;
} else if (image.getWidth() <= 0) {
return null;
} else if (image.getHeight() <= 0) {
return null;
} else if (col < 0 || col >= image.getHeight()) {
return null;
} else if (row < 0 || row >= image.getWidth()) {
return null;
} else {
return image.getRGB(row, col);
}
}

static boolean isCenterOfCircle(int row, int col, int r, BufferedImage image) {

if(getPixel(row,col,image) == getPixel(row+r,col,image)
|| getPixel(row,col,image) == getPixel(row-r,col,image)
|| getPixel(row,col,image) == getPixel(row,col+r,image)
|| getPixel(row,col,image) == getPixel(row,col-r,image)){
return true;
}else{
return false;
}
}

static void findCircle(int r, BufferedImage image, int w, int h) {

// graphical output
Graphics2D g2 = image.createGraphics();

// use red
g2.setColor(Color.RED);

// for each pixel in the image, search for a circle, if found draw it in red
for (int row=0; row<image.getWidth(); row++) {
for (int col=0; col<image.getHeight(); col++) {
if (isCenterOfCircle(row,col,r,image)) {
drawCircle(row,col,r,g2);
}
}

}
}
}```
Last edited by lisa92; January 26th, 2013 at 06:06 PM.