Filters provide options that evaluate an entire picture or clusters of pixels and then modify pixels based on context. If you’re familiar with a filter or effect from another application, you’ll be comfortable with filter controls in QuarkXPress as well.

• The Despeckle filter detects the edges in a picture and blurs all of the picture except those edges. It removes noise while preserving detail, and can be useful for removing dust from a scanned image.
• The Gaussian Blur filter smoothes transitions by averaging pixels next to hard edges of defined lines and shaded areas in a picture. By checking Blur Picture and/or Blur Mask, you can apply this filter separately to pictures and their alpha masks.
• The Unsharp Mask filter compares pixel values in a defined area to the specified threshold value. If a pixel has a lower contrast value than the threshold value, its contrast is increased.
• The Find Edges filter outlines the edges of a picture with dark lines against a white background.
• The Solarize filter blends negative and positive areas of a picture, producing a photographic solarization effect. To use the Solarize dialog box, enter a Threshold value in the field or drag the slider. The value specifies which pixels to modify — those with values lower than the threshold are considered negative and those with values higher than the threshold are considered positive. The pixel values are then inverted.
• The Diffuse filter shuffles pixels so the picture looks less focused. By default, the effect applies to the picture and to the mask selected for the picture in the Item > Modify > Picture tab.
• The Emboss filter makes areas of the picture appear raised or stamped.
• When the Emboss filter is applied, you can specify the direction from which to raise or stamp the picture using the Embossing Effects filter. Click the directional arrows in the Embossing Effects dialog box to apply different directions. For example, clicking the upper-right arrow might specify that when you pushed a stamp onto an object, you pushed slightly to the right, smearing the stamp in that direction.
• The Edge Detection filter displays only edges of the picture, suppressing the remaining colors. The Edge Detection dialog box provides two mathematical methods for determining edges: Sobel and Prewitt. The Sobel method might be more precise because it considers more surrounding pixels in its calculations.
• The Trace Contour filter thinly outlines the transitions of major brightness areas for each color channel, producing a black-and-white outline of the picture. You have the option to invert the results as well.
• The Add Noise filter applies random pixels to a picture to simulate pictures shot using high-speed film. The filter applies an even pattern to shadow tones and midtones while adding a smoother, more saturated pattern to the picture’s lighter areas.
• The Median filter reduces or eliminates the look of motion on a specified region of a picture. The effect searches pixels of similar brightness, and replaces the central pixel with the median brightness value of the searched pixels; pixels that differ significantly from adjacent pixels remain unaffected.