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    ArrayIndexOutOfBounds error


    This program takes as input an image, scans it and highlights circles in red. However I get an ArrayOutOfBounds exception at the last method when I call drawCircle(). I dont know how to fix it.

    Code:
    public class Assig1 {
    
        public static void main(String[] args) {
            try {
                // arg 0 is the input image name
                BufferedImage img = ImageIO.read(new File(args[0]));
    
                // 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);
                
                //----
                // write out the image
                File outputfile = new File("outputimage1.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,BufferedImage img,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);
            }
        
    }
    
        static void findCircle(int r,BufferedImage img, int w, int h) {
    
        	//getting all the pixels from an image
        	int[][] pixels = new int[w][h];
    
        	for( int i = 0; i < w; i++ ){
          	 	 for( int j = 0; j < h; j++ ){
             		   pixels[i][j] = img.getRGB( i, j );
          	 	 }
        	}
        	
        	 // graphical output
            Graphics2D g2 = img.createGraphics();
            // use red
            g2.setColor(Color.RED);
        	
        	
        	for (int i1=0; i1<pixels.length; i1++) {
        	     for (int j1=0; j1<pixels[i1].length; j1++) {
        	         
        	    	 if(pixels[i1][j1] != pixels[i1+r][j1]
        	     			|| pixels[i1][j1] != pixels[i1-r][j1]
        	     			|| pixels[i1][j1] != pixels[i1][j1+r]
        	     			|| pixels[i1][j1] != pixels[i1][j1-r]){
        	     		drawCircle(i1,j1,r,img,g2);
        	     	}
        	     }
        	  
        	 }
        }
    }
  2. #2
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    I get an ArrayOutOfBounds exception
    Please copy the full text of the error message and post it here. It shows where the exception happened and the value of the index.

    Remember array indexes range from 0 to the array length-1
  4. #3
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    ArrayIndexOutOfBoundsException : -3
    at Assig1.findCircle<Assig1.java:112>
    at Assig1.main<Assig1.java:42>
  6. #4
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    Look at the values of all the indexes used on line 112 and see if any of them could be -3.

    If you can not tell by looking, add a println statement that prints out the values of all the indexes used on that line to see which one has the value of -3.
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    Updated


    in the findCircle method I put i1 and j1 to start at r+1. (ie so that the image starts searching at after a given radius and not before that) but I still get same error this time instead of 3 it is 321

    Code:
     static void findCircle(int r,BufferedImage img, int w, int h) {
    
        	long timeBefore = System.currentTimeMillis();
        	
        	//getting all the pixels from an image
        	int[][] pixels = new int[w][h];
    
        	for( int i = 0; i < w; i++ ){
          	 	 for( int j = 0; j < h; j++ ){
             		   pixels[i][j] = img.getRGB( i, j );
          	 	 }
        	}
        	
        	 // graphical output
            Graphics2D g2 = img.createGraphics();
            // use red
            g2.setColor(Color.RED);
        	
        	
        	for (int i1=r+1; i1<pixels.length; i1++) {
        	     for (int j1=r+1; j1<pixels[i1].length; j1++) {
        	         
        	    	 if(pixels[i1][j1] != pixels[i1+r][j1]
        	     			|| pixels[i1][j1] != pixels[i1-r][j1]
        	     			|| pixels[i1][j1] != pixels[i1][j1+r]
        	     			|| pixels[i1][j1] != pixels[i1][j1-r]){
        	     		
        	     		
        	     		//Question 3a). Measuring time
        	     		long timeAfter = System.currentTimeMillis();
        	     	    long elapsed = timeAfter - timeBefore;
        	     	    System.out.println("elapsed:" + elapsed);
        	     	    
        	     	   drawCircle(i1,j1,r,img,g2);
        	     	}
        	     }
        	  
        	 }
        }
    }
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    Do you see what variable's content is causing the problem? When you fidn that, Then you need to check your algorithm to see why that variable has values outside the range of array indexes.

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