Alpha composite of two images in Pillow

Overview:

An alpha channel of an image represents its transparency.

Pillow the Python Image Processing Library provides alpha compositing of images through the Image class method alpha_composite().

When the value of alpha channel of one image is 0 - and of another image is 1, the alpha_composite() will display only the second image since its pixels are opaque.

When the value of alpha channel of one image is 1 - and of another image is 0, the alpha_composite() will display only the first image as the pixels of the first image are opaque.

When alpha channels of both the images are opaque, both the pixels are to be displayed - Transparency levels are determined by the color of the pixel's' from both the images equally.

Example:

from PIL import Image

# Function to change the image size
def changeImageSize(maxWidth,
maxHeight,
image):

widthRatio = maxWidth/image.size[0]
heightRatio = maxHeight/image.size[1]

newWidth = int(widthRatio*image.size[0])
newHeight = int(heightRatio*image.size[1])

newImage = image.resize((newWidth, newHeight))
return newImage

# Take two images
image1 = Image.open("./sky.png")
image2 = Image.open("./plane.png")

# Make the sizes of images uniform
image3 = changeImageSize(800, 500, image1)
image4 = changeImageSize(800, 500, image2)

# Make sure the images have alpha channels
image3.putalpha(1)
image4.putalpha(1)

# Display the images
image3.show()
image4.show()

# Do an alpha composite of image4 over image3
alphaComposited = Image.alpha_composite(image3, image4)
#alphaBlended = Image.blend(image4, image3,.1)
#alphaBlended.show()

# Display the alpha composited image
alphaComposited.show()

Output:

Image1 of the alpha composite:

Image2 of the alpha composite:

Image2 of the alpha composite

The Alpha Composite of two images:

The alpha composite image of two images - Python - Pillow Example