Custom Range Threshold¶

Creates a binary image (mask) and a masked image from an RGB or grayscale image based on the user defined threshold values. The threshold color-spaces that can be used are grayscale, RGB, HSV, or LAB.

plantcv.threshold.custom_range(img, lower_thresh, upper_thresh, channel='RGB')

returns mask, masked_img

• Parameters:
  • img - RGB image data
  • lower_thresh - List of lower threshold values (0-255)
  • upper_thresh - List of upper threshold values (0-255)
  • channel - Color-space channels of interest (either 'RGB', 'HSV', 'LAB', or 'gray')
• Context:
  • Used to help differentiate plant and background
• Example use:
  • Use In NIR Tutorial

from plantcv import plantcv as pcv

# Set global debug behavior to None (default), "print" (to file), or "plot" (Jupyter Notebooks or X11)

pcv.params.debug = "plot"

# Read in the image

img, path, filename = pcv.readimage(filename="rgb_example_img.jpg")

# Create masked image from a color image based RGB color-space and threshold values. 
# for lower and upper_thresh list as: thresh = [red_thresh, green_thresh, blue_thresh]

mask, masked_img = pcv.threshold.custom_range(img=img, lower_thresh=[10,10,10], upper_thresh=[100,255,100], channel='RGB')

Original image (RGB Color-space)

Masked image (RGB Color-space)

Mask (RGB Color-space)

# Read in the image
img, path, filename = pcv.readimage(filename="hsv_example_img.jpg")

# Create masked image from a color image based HSV color-space and threshold values. 
# for lower and upper_thresh list as: thresh = [hue_thresh, saturation_thresh, value_thresh]

mask, masked_img = pcv.threshold.custom_range(img=img, lower_thresh=[30,65,20], upper_thresh=[70,255,220], channel='HSV')

Original image (HSV Color-space)

Masked image (HSV Color-space)

Mask (HSV Color-space)

# Read in the image
img, path, filename = pcv.readimage(filename="lab_example_img.jpg")

# Create masked image from a color image based LAB color-space and threshold values.
# for lower and upper_thresh list as: thresh = [L_thresh, A_thresh, B_thresh]
mask, masked_img = pcv.threshold.custom_range(img=img, lower_thresh=[0,0,158], upper_thresh=[255,255,255], channel='LAB')

Original image (LAB Color-space)

Masked image (LAB Color-space)

Mask (LAB Color-space)

# Read in the image
gray_img, path, filename = pcv.readimage(filename="gray_example_img.jpg")

# Create masked image based grayscale color-space and threshold values. 
# Note that a grayscale image is used. pcv.threshold.custom_range works with both RGB and gray input images. 
mask, masked_img = pcv.threshold.custom_range(img=gray_img, lower_thresh=[39], upper_thresh=[100], channel='gray')

Original image (Grayscale Color-space)

Masked image (Grayscale Color-space)

Mask (Grayscale Color-space)

Source Code: Here