Blend Two Images Using An Alpha Value


  • An alpha channel in an image introduces transparency to the Image.


  • Alpha blending combines two images by applying an alpha value to the images.


  • Pillow –Python Image Processing Library provides blend() method as part of the Image class implementation.


  • When Image1 and Image2 are blended using alpha value 0, Image1 is returned as and vice versa when the alpha value is 1.


  • When the alpha value varies from 0 to 1 and beyond, interpolation is used to determine the color value given by the formula


out=((int) in1[x] + alpha * ((int) in2[x] - (int) in1[x]));


from PIL import Image

# Function to change the image size
def changeImageSize(maxWidth, 
    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 for blending them together   
image1 ="./sky1.png")
image2 ="./spaceship1.png")

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

# Make sure images got an alpha channel
image5 = image3.convert("RGBA")
image6 = image4.convert("RGBA")

# Display the images

# alpha-blend the images with varying values of alpha
alphaBlended1 = Image.blend(image5, image6, alpha=.2)
alphaBlended2 = Image.blend(image5, image6, alpha=.4)

# Display the alpha-blended images


Image1 used in blending:

Image1 for blending using an alpha value - Pillow example

Image2 used in blending:

Image2 for blending using an alpha value - Pillow example

Alpha blended Image - alpha=0.2:

Alpha blended image 1, alpha = 0.2

Alpha blended Image - alpha=0.4:

Alpha blended image 2 - alpha = 0.4

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