c# - image comparisson, having trouble grabbing the x and y coordinate of the pixels -

i have following code compares 2 images , outputs how many pixels different. i'm trying figure out how make output x , y coordinates of pixels. have idea?

        public int count2;         public boolean flag;         private void button1_click(object sender, eventargs e)         {              string img1_ref, img2_ref;             //this image 10x10             bitmap img1 = properties.resources.black;             //this image screenshot             bitmap img2 = properties.resources.bigimg;                 (int = 0; < img1.width; i++)                 {                     (int j = 0; j < img1.height; j++)                     {                          img1_ref = img1.getpixel(i, j).tostring();                         img2_ref = img2.getpixel(i, j).tostring();                         if (img1_ref != img2_ref)                         {                             count2++;                             flag = false;                             break;                         }                     }                 }                 if (flag == false)                     messagebox.show(count2 + " wrong pixels found");           } 

these images, , small black square should found in middleish of big image:

how having list stores wrong pixels?

list<point> wrongpixels = new list<point>(); [...] if (img1_ref != img2_ref){   wrongpixels.add(new point(i,j));   [...] } [...] (int i=0, max=wrongpixels.count;i<max;i++){   messagebox.show("wrong pixel at: " + wrongpixels[i].tostring()); }