Histogram Of Image Colors

Overview:

  • Pillow - the Python Image Processing Library provides several methods to extract information pertaining to an image. The histogram() method provides information on counts of different colors/bands.

 

  • histogram() method returns a list of pixel counts for each band present in the image. The list will have all the counts concatenated for each band.

 

  • If an image is of mode "RGB" then for each of band/color a list of pixel counts will be returned, totaling 768.

 

  • In other words, for an RGB image, the histogram() method gives information on how many kind of Red, Green and Blue pixels are present in the image for each 256 types of red, 256 types of green and 256 types of blue.

 

Example:

from PIL import Image

import matplotlib.pyplot as plt

 

def getRed(redVal):

    return '#%02x%02x%02x' % (redVal, 0, 0)

 

def getGreen(greenVal):

    return '#%02x%02x%02x' % (0, greenVal, 0)

   

def getBlue(blueVal):

    return '#%02x%02x%02x' % (0, 0, blueVal)

 

 

# Create an Image with specific RGB value

image = Image.open("./peacock.jpg")

 

# Modify the color of two pixels

image.putpixel((0,1), (1,1,5))

image.putpixel((0,2), (2,1,5))

 

# Display the image

image.show()

 

# Get the color histogram of the image

histogram = image.histogram()

 

# Take only the Red counts

l1 = histogram[0:256]

 

# Take only the Blue counts

l2 = histogram[256:512]

 

# Take only the Green counts

l3 = histogram[512:768]

 

plt.figure(0)

 

# R histogram

for i in range(0, 256):

    plt.bar(i, l1[i], color = getRed(i), edgecolor=getRed(i), alpha=0.3)

 

# G histogram

plt.figure(1)

for i in range(0, 256):

    plt.bar(i, l2[i], color = getGreen(i), edgecolor=getGreen(i),alpha=0.3)

 

 

# B histogram

plt.figure(2)

for i in range(0, 256):

    plt.bar(i, l3[i], color = getBlue(i), edgecolor=getBlue(i),alpha=0.3)

 

plt.show()

 

Output:

The image for which histogram is created:

Image for which histogram is taken using Python-Pillow

Histogram of red pixels:

Histogram of red color pixels present in the image - Pillow Example

Histogram of green pixels:

Histogram of green color pixels present in the image - Pillow Example

Histogram of blue pixels:

Histogram of blue color pixels present in the image - Pillow Example


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