The document discusses how to generate image histograms using the Pillow library in Python. It explains that the histogram() method returns a list of pixel counts for each color band in an image. It provides an example of generating histograms for the red, green, and blue color channels of an RGB image, displaying the counts for each channel in separate figures. The code sample modifies two pixel colors in an image, gets the image histogram, and plots the histograms for each color channel.

1. Image Histograms using
Pillow
pythontic.com

2. Image Histogram using Python - Pillow
• histogram() method provides counts of
different colors/bands of an image.
• returns a list of pixel counts for each band
present in the image
• Example: For an image with mode "RGB” – for
list of pixel counts for each color is returned -
totaling 768.

3. Image Histogram using Python - Pillow
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")

4. Image Histogram using Python - Pillow
# 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]

5. Image Histogram using Python - Pillow
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()

6. Image Histogram using Python - Pillow