The Image Filters PlugIn allows you to filter/enhance images displayed by gPhotoShow/Wallpaper Slideshow in several ways.
This filter allows to adjust the Gamma (or gray point) of an image. It can be useful to adapt your pictures to a monitor with a different gamma value or just to make pictures lighter (or darker) without affecting whites and blacks.
This filter is useful to adjust image appearance and contrast, the histogram of the image is stretched to fill all possible values. In this way global contrast is enhanced and over/under exposed images get a much better looking. Auto Levels works only on luminosity and doesn't affect colors.
Local Contrast Enhancement
This filters uses unsharp mask with a large radius to improve local contrast. This kind of action is also known as "Defog" or "Haze removal".
This filter improves sharpness of the image. Even if your pictures already have been sharpened this filter helps to improve sharpness after they are resized by gPhotoShow/Wallpaper Slideshow
This filter allows to convert pictures to black & white and to optionally add a sepia tone. There are several algorithms to convert to B&W image