Sobel Filter

This is a filtering method used to identify and highlight coarse changes in pixel intensity based on the 1st derivative.

sobel_filter(img, dx,dy,k, device, debug=None)

returns device, filtered image

  • Parameters:
    • img - binary image object. This image will be returned after filling.
    • dx - derivative of x to analyze (0-3)
    • dy - derivative of y to analyze (0-3)
    • k - apertures size used to calculate 2nd derivative filter, specifies the size of the kernel (must be an odd integer: 1,3,5...)
    • device - Counter for image processing steps
    • debug - None, "print", or "plot". Print = save to file, Plot = print to screen. Default = None
  • Context:
    • Used to define edges within and around objects
  • Example use:

Original grayscale image


import plantcv as pcv

# Apply to a grayscale image
# Filtered image will highlight areas of coarse pixel intensity change based on 1st derivative
device, lp_img = pcv.sobel_filter(img, 1, 0, 1, device, debug="print")
device, lp_img = pcv.sobel_filter(img, 0, 1, 1, device, debug="print")

Sobel filtered (x-axis)


Sobel filtered (y-axis)