Thresholding Tool

Interactively select intensity level for image thresholding.

THRESH_TOOL launches a GUI (graphical user interface) for thresholding an intensity input image, IM. IM is displayed in the top left corner. A colorbar and IM's histogram are displayed on the bottom. A line on the histogram indicates the current threshold level. A binary image is displayed in the top right based on the selected level. To change the level, click and drag the line. The output image updates automatically.
There are two ways to use this tool.

Mode 1 - nonblocking behavior:
THRESH_TOOL(IM) launches GUI tool. You can continue using the MATLAB Desktop.Since no results are needed, the function does not block execution of other commands.

THRESH_TOOL(IM,CMAP) allows the user to specify the colormap, CMAP. If not specified, the default colormap is used.

THRESH_TOOL(IM,CMAP,DEFAULTLEVEL) allows the user to specify the default threshold level. If not specified, DEFAULTLEVEL is determined by GRAYTHRESH. Valid values for DEFAULTLEVEL must be consistent with the data type of IM for integer intensity images: uint8 [0,255], uint16 [0,65535], int16 [-32768,32767].

Example
x = imread('rice.png');
thresh_tool(x)
%no return value, so MATLAB keeps running

Mode 2 - blocking behavior:
LEVEL = THRESH_TOOL(...) returns the user selected level, LEVEL, and MATLAB waits for the result before proceeding. This blocking behavior mode allows the tool to be inserted into an image processing algorithm to support an automated workflow.

[LEVEL,BW] = THRESH_TOOL(...) also returns the thresholded binary output image, BW.

Example
x = imread('rice.png');
lev = thresh_tool(x) %MATLAB waits for GUI tool to finish

See also colormap, graythresh, im2bw.