Edge Finding

The Edge Finding options allow you to control how Fluid Mask analyses all or part of your image. When you open Fluid Mask, the program calculates reasonable values for these options. Sometimes you may find it helpful to adjust the settings with the goal of finding the important edges in your image, while at the same time keeping the total number of objects as small as possible.

The settings you make on the main Edge Finding palette apply to the entire image. However, sometimes different areas of an image have such varied characteristics that it is difficult to find settings that work for the entire image. To solve this problem, you can create a patch over part of an image using the Patch tools and apply a unique set of edge finding options to just that area using the Patch Properties dialog.

The edge finding settings all change the number and size of the objects Fluid Mask will detect in an image. In general, the best way to dial in the optimum settings is to start with the default settings and then work from top to bottom of the Options Palette. In other words, find the best edge width threshold first, then the best setting for the number of objects, and so on.

• Edge Width Threshold: sets the minimum width in pixels of a color or texture transition that Fluid Mask will recognize as an edge. If you set a small threshold, Fluid Mask will find many in-focus and sharp edges; if you set a larger threshold, Fluid Mask will find fewer but broader edges such as found with out of focus edges.
• Number of Objects: Sets how finely Fluid Mask divides an image into objects. The higher the setting, the more objects Fluid Mask will identify.
  
  When working with fine detail like tree leaves and branches, move the slider all the way to the right – this is the optimal setting for finding these kinds of objects. You will note that the Show Object Edges check box at the bottom of the screen has been turned off at this setting, as indicating such fine objects is not useful.
• Defaults button: Restores the edge detection settings to the original, calculated values.
• Revert button: Restores the edge detection settings to the last settings you applied.
• Apply button: Applies the current settings and re-analyzes the image.

Advanced Options

Click the Advanced button to reveal the advanced options. These options do not need to be adjusted for most images.

• Edge Contrast: Sets how much difference in color there must be for an edge to be identified.
• Choose Low to have Fluid Mask identify low contrast changes as an image edge.
•  Choose Medium or High when there is plenty of contrast between the image to be cut out and the background. A higher setting will result in fewer edges — useful for complex images..
• Filter out Texture: Sets how Fluid Mask should combine highly textured areas.
• Choose Fine to have Fluid Mask treat each object within a textured area separately, such as when you are cutting out leaves against the sky.
• Choose Coarse to have Fluid Mask treat textured areas as a single area, such as when you want a lawn to be treated as a single object with one edge rather than as several small objects with many edges.