HSV Threshold
The class HSVThreshold is a tool for clustering problems
in HSV (Hue, Saturation, and Value) color space for color-based pixel
separation. The main purpose of this tool is to support semi-automated
color-based segmentation. Particularly, this tool provides users the decision
support about valid pixel value ranges for specific types of object detection.
Description: The class operates in three ranges of
HSV values. Points within the user-specified value ranges are appeared in the
result image, both as RGB and HSV images. In each scrollbar, a user can adjust
the upper and lower limits of the pixel values, and can fix the dynamic value
range by checking the “Fix Range” option. For example, the lower/upper limit
will move automatically while keeping the same dynamic value range when changing
the upper/lower limit.

Setup: By default, both RGB and HSV image are
displayed from the main Im2Learn frame. The two windows dynamically show the
classified images when a user adjusts the threshold value ranges.
For large image processing, such as “svs” format, a user
can directly load the image into the HSV threshold tool independently from the
main Im2Learn frame by pressing “Load” button. If a sub-sampled overview image
is available, as a same filename with “tif” extension, an overview window will
be displayed where a user can interactively select the currently displayed
region (marked as red cross).

Run: First, select a sub-region from the overview
image to load a 200 by 200 pixel neighborhood from the large image to the RGB
and HSV windows. Next, change the Hue, Saturation, and Value range to acquire
the thresholded image. The number of valid (displayed) pixels is shown in the
title of the tool as “Positive pixel count” with the percentage with respect to
the total number of the pixels in the sub-region.
“Change Region” button can be used to load an overview
image with different filename. Note that the overview image has to be a 1:200
sub-sampled image from the original svs image, for example, an image sub-sampled
by the factor of 200.