How to Combine Multiple Images into One in Go?

How to Combine Images in Go

In Go, you can manipulate images to create a single larger image from multiple smaller ones. To do this, follow the steps below:

1. Load the Images: Use os.Open to open the image files and image.Decode to decode the images into image.Image objects.
2. Create the Large Image: Determine the dimensions of the final image and use image.NewRGBA to create an empty image with those dimensions.
3. Draw the First Image: Use draw.Draw to draw the first image onto the large image. Specify the starting point and the source image.
4. Calculate the Starting Point of the Second Image: Determine the offset of the second image in the final image. This is typically the width of the first image.
5. Draw the Second Image: Use draw.Draw to draw the second image onto the large image. Specify the starting point and the source image.
6. Export the Final Image: Use image.Encode to export the combined image to a file in the desired format.

For example, to create a horizontal concatenation of two images, you can use the following code:

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

func main() {
    // Load the images
    img1, err := os.Open("test1.jpg")
    if err != nil {
        fmt.Println(err)
    }
    img2, err := os.Open("test2.jpg")
    if err != nil {
        fmt.Println(err)
    }
    img1, _, err = image.Decode(img1)
    if err != nil {
        fmt.Println(err)
    }
    img2, _, err = image.Decode(img2)
    if err != nil {
        fmt.Println(err)
    }

    // Create the large image
    r1 := img1.Bounds()
    r2 := img2.Bounds()
    r := image.Rectangle{image.Point{0, 0}, r2.Max}
    rgba := image.NewRGBA(r)

    // Draw the images
    draw.Draw(rgba, r1, img1, image.Point{0, 0}, draw.Src)
    draw.Draw(rgba, r2, img2, image.Point{r1.Dx(), 0}, draw.Src)

    // Export the final image
    out, err := os.Create("output.jpg")
    if err != nil {
        fmt.Println(err)
    }
    
    var opt jpeg.Options
    opt.Quality = 80
    
    jpeg.Encode(out, rgba, &opt)
}

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