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:

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


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