How to blend and composite images with transparency in Go?

To blend and composite images with transparency in Go, you can use the draw package from the image package. The draw package provides several functions for manipulating and combining images. Here's how you can blend and composite images with transparency:

Import the required packages:

import (
    "image"
    "image/draw"
    "os"
)

Load the images that you want to blend:

// Open the source image
sourceFile, _ := os.Open("source.png")
sourceImage, _, _ := image.Decode(sourceFile)
sourceFile.Close()

// Open the destination image
destFile, _ := os.Open("destination.png")
destImage, _, _ := image.Decode(destFile)
destFile.Close()

Create a new RGBA image with the same size as the destination image:

// Create an RGBA image with the same size as the destination image
rgba := image.NewRGBA(destImage.Bounds())

Use the draw.Draw() function to blend the source image onto the destination image:

// Blend the source image onto the destination image
draw.Draw(rgba, destImage.Bounds(), destImage, image.Point{}, draw.Src)
draw.DrawMask(rgba, sourceImage.Bounds(), sourceImage, image.Point{}, &image.Uniform{color.Transparent}, image.Point{}, draw.Over)

In the code above, draw.Draw() is used to draw the destination image onto the rgba image with draw.Src mode, which replaces the destination pixels. Then, draw.DrawMask() is used to draw the source image onto the rgba image with draw.Over mode, which blends the source pixels with the existing pixels in the destination.

Save the blended image to a file:

// Save the blended image
outputFile, _ := os.Create("output.png")
png.Encode(outputFile, rgba)
outputFile.Close()

That's it! You have successfully blended and composited images with transparency in Go. Just replace "source.png", "destination.png", and "output.png" with the appropriate file paths.