Increase the zoom level to edit images with more precision, or reduce it to see more of the image.
At zoom levels that aren't multiples of 100%, parts of the image may appear to move when the user interacts with it. Other minor redraw glitches may also occur at such zoom levels.
At zoom levels of 400% or greater that are also multiples of 100%, you can to more accurately edit individual pixels.
The first picture shows the Text tool icon, while the latter shows it at 600% zoom with the grid on.
Another way of zooming when not drawing is to scroll the Ctrl.while holding