The Photocopy filter modifies the active layer or selection so that it looks like a black and white photocopy, as if toner transfered was based on the relative darkness of a particular region. This is achieved by darkening areas of the image which are measured to be darker than a neighborhood average, and setting other pixels to white.
This parameter controls the size of the pixel neighbourhood over which the average intensity is computed and then compared to each pixel in the neighborhood to decide whether or not to darken it. Large values result in very thick black areas bordering the regions of white and much less detail for black areas. Small values result in less toner overall and more details everywhere.
With this option, you can set photocopy sharpness, from 0.0 to 1.0.
This parameter controls the amount of black color added to the image. Small values make the blend from color regions to blackened areas smoother and dark lines themselves thinner and less noticeable. Larger values make the lines thicker, darker and sharper. The maximum value makes the lines aliased. The best, most natural results are usually achieved with an intermediate value. Values vary from 0.0 to 1.0.
This parameter increases white pixels percentage.