The mask module determines how the filtered results are presented to the sink. One possibility is to always select the filtered image. Indeed, this is the default behavior of the program, since it allows the experimenter to directly examine the filtered video. Another commonly used option is to use a color mask. The color mask is typically used when the filter computes a binary image. For example, the edge filter and the motion filter both do this. The foreground and background parameters to the color mask specify the color of the true and false pixels respectively. Hence, to make edges appear as blue lines on a white background, the foreground color would be a number representing blue and the background color would be a number representing white.
Note: The mapping of colors to numbers is a function of your Xdisplay. I recommend trying different values of these parameters to get the colors you want.
In addition, the value -1 for the foreground or background specifies a "transparent" color for those pixels. In this case, the true or false pixels are replaced by the corresponding unfiltered pixels. Hence, to display video where the edges are hilighted in blue, one would specify the foreground color to be blue and the background color to be -1.
Parameters to the filters and the masks may be changed while the program is running by clicking on the control panel button. Go ahead and try different values to see how they affect the output.
Click here for descriptions of the different processing modules.
