CODEWITHSUNDEEP
imagenumpyopencv
scholcode
scholcode

Reputation: 33

Pixel extraction using image masking?

I have two pictures. enter image description here

enter image description here

I want to extract the pixels in the regions marked by their respective color. (The normal distribution of the pixels in yellow and red)

I know opencv supports bitwise operation, however, I've only seen it being done with black/white mask.

I thought about using np.where(), I am curious to see if there's a better solution?

Upvotes: 0

Views: 546

Answers (1)

Mark Setchell
Mark Setchell

Reputation: 207345

You can count the number of red/yellow pixels like this:

#!/usr/bin/env python3

import cv2
import numpy as np

# Load image
im = cv2.imread('abYaj.png')

# Make mask of red pixels - True where red, false elsewhere
redMask = (im[:, :, 0:3] == [0,0,255]).all(2)

# Count red pixels
redTotal = np.count_nonzero(redMask)            # redTotal=44158

# Make mask of yellow pixels
yellowMask = (im[:, :, 0:3] == [0,255,255]).all(2)

# Count yellow pixels
yellowTotal = np.count_nonzero(yellowMask)      # yellowTotal=356636

Alternatively, you could just use ImageMagick in the Terminal to count them and write no code at all:

magick identify -verbose abYag.png

Image:
  Filename: abYaj.png
  Format: PNG (Portable Network Graphics)
  Mime type: image/png
  Class: DirectClass
  Geometry: 1024x1024+0+0
  Units: Undefined
  Colorspace: sRGB
  ...
  ...
  Colors: 3
  Histogram:
    647782: (0,0,0,0) #00000000 none
    44158: (255,0,0,255) #FF0000FF red             <--- HERE
    356636: (255,255,0,255) #FFFF00FF yellow       <--- HERE
  Rendering intent: Perceptual
  ...
  ...

Upvotes: 2

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