Gradient Energy mode determines the sharpness of an image by summing the squares of the differences of adjacent pixels over an entire image. Sharper images generally have greater pixel-to-pixel contrast values and generate higher result scores.
An Image Sharpness tool uses a 3-pixel kernel to generate the score:
The Gradient Energy mode supports a smoothing parameter, set to 0 by default, which you can increase to remove potential high frequency image noise from consideration.
Some notes about Gradient Energy mode:
- Produces reliable results for most types of images
- Good for reducing high frequency image noise by using a non-zero smoothing parameter
- Requires more processing time when using a non-zero smoothing parameter, and can reduce the original clarity of the image if you choose a smoothing parameter that is too high