1, Open a transparent image 400/400 px. We work comfortably and later and do smaller.

2 In the Rectangle Selection tool, select Circle In Rectangle Selection tool, select circle, or ellipse, this depends on the work that we will do:

3 º seek with your mouse cursor point more or less accurate picture. If this is 400/400 px, the exact coordinates would be x: 200 y: 200 Let's pay close attention to the bottom of the screen on the right side of your monitor:

and see that these numbers tell us. We note that we have an image of 400 by 400 by 16 million colors and between the parentheses is the number that interests us most at this time as this where I had just pointing the mouse cursor when I made the catch.

en el 201 con muchísimo pulso y gran paciencia, conseguiremos que Y también este en el 200 justo. Are the coordinates and tells us that X is at point 200 and Y at 201 with a lot of pulse and great patience, we will make And just this on the 200. Then we have found the absolute center of our image. Once you have the point x: 200 y: 200, select the Rectangle tool, set to circle and hold the mouse button, we'll pull it from the center up and left. As we look back on the right side of the screen:

Indicates that at this point, the circle that are created will be a measure of 192 wide by 192 high. To check, you can fill in the circle with any color, copy and paste as a new image. You will see that the measures are those that mark the position that you point the box in the screenshot above.

I hope this little tip, the difficulties of selecting an exact area, with an accurate, you are easier. It's about pulse and patience, patience and exercise safely. I seguara that you will get it the second or third attempt