A modification of Bob Dougherty's BandPass2 filter to threshold colour RGB images in the HSB, RGB, CIE Lab or YUV spaces.
The plugin suports extracting the range of HSB, RGB, CIE Lab or YUV values from a sample ROI (any type) to set (move in the x and y directions) stretch and rotate the filters automatically. Extract the files from the zip archive and put them somewhere in the plugins directory (or subdirectory). The Threshold_Colour entry will appear in the Plugins hierarchy, depending of the subdirectory which the plugin is copied to (I suggest the name “Segmentation” to keep all thresholding plugins).
The [Macro] button generates a macro that is sent to the Recorder window (if active) based on the current plugin settings.
The zip file also includes RGB2YUV and RGB2Lab plugins which are necessary for that macro (note that these plugins convert an RGB image to YUV and CIE Lab colour spaces but with values mapped into an 8-bit space).
The Threshold_Colour plugin, source and documentation are based at http://www.dentistry.bham.ac.uk/landinig/software/software.html.