Home >Backend Development >Golang >How to Concatenate Images in Golang?
Although Go provides robust image manipulation capabilities, users often face challenges in creating a single image from multiple smaller ones. Specifically, how can two PNG or JPEG files be concatenated to form a comprehensive image?
The provided code reveals the reading of PNG files into an RGBA format:
imgFile, err := os.Open(path) if err != nil { return Image{}, err } img, _, err := image.Decode(imgFile) if err != nil { return Image{}, err } rgba := image.NewRGBA(img.Bounds()) if rgba.Stride != rgba.Rect.Size().X*4 { return Image{}, fmt.Errorf("unsupported stride") } draw.Draw(rgba, rgba.Bounds(), img, image.Point{0, 0}, draw.Src)
However, the crux of the issue lies in understanding how to combine multiple RGBA datasets into a single image.
The solution involves creating a new, empty image (NewRGBA) of sufficient size to accommodate both original images. Subsequently, the Draw method can be employed to overlay each image onto designated portions of the extended image:
// Load two images imgFile1, err := os.Open("test1.jpg") if err != nil { fmt.Println(err) } imgFile2, err := os.Open("test2.jpg") if err != nil { fmt.Println(err) } img1, _, err := image.Decode(imgFile1) if err != nil { fmt.Println(err) } img2, _, err := image.Decode(imgFile2) if err != nil { fmt.Println(err) } // Starting position of the second image sp2 := image.Point{img1.Bounds().Dx(), 0} // New rectangle for the second image r2 := image.Rectangle{sp2, sp2.Add(img2.Bounds().Size())} // Rectangle for the big image r := image.Rectangle{image.Point{0, 0}, r2.Max} // Create a new image rgba := image.NewRGBA(r) // Draw the two images draw.Draw(rgba, img1.Bounds(), img1, image.Point{0, 0}, draw.Src) draw.Draw(rgba, r2, img2, image.Point{0, 0}, draw.Src) // Export the 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)
Note: This method preserves the height of the second image. If the first image is taller, it will be cropped.
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