How to create thumbnails and smaller versions of images in Go?

To create thumbnails and smaller versions of images in Go, you can use the github.com/nfnt/resize package. This package provides an easy way to resize images while maintaining their aspect ratio.

Here's an example code that demonstrates how to create thumbnails and smaller versions of images using this package:

package main

import (
	"fmt"
	"image"
	"image/jpeg"
	"log"
	"os"

	"github.com/nfnt/resize"
)

func main() {
	// Open the image file
	file, err := os.Open("input.jpg")
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	// Decode the image
	img, _, err := image.Decode(file)
	if err != nil {
		log.Fatal(err)
	}

	// Create a thumbnail with a maximum width of 100 pixels
	thumbnail := resize.Thumbnail(100, 100, img, resize.Lanczos3)

	// Save the thumbnail to a file
	outputFile, err := os.Create("thumbnail.jpg")
	if err != nil {
		log.Fatal(err)
	}
	defer outputFile.Close()

	jpeg.Encode(outputFile, thumbnail, nil)

	fmt.Println("Thumbnail created!")

	// Create a smaller version of the image with a width of 500 pixels
	small := resize.Resize(500, 0, img, resize.Lanczos3)

	// Save the smaller version to a file
	outputFile, err = os.Create("small.jpg")
	if err != nil {
		log.Fatal(err)
	}
	defer outputFile.Close()

	jpeg.Encode(outputFile, small, nil)

	fmt.Println("Smaller version created!")
}

In this example, we first open the image file using os.Open and decode it using the image.Decode function. Then, we create a thumbnail of the image using resize.Thumbnail by specifying a maximum width and height for the thumbnail. We also specify the resizing algorithm to be used (in this case, resize.Lanczos3).

Next, we save the thumbnail to a file using jpeg.Encode. The same process is repeated to create a smaller version of the image, with a specific width, using resize.Resize.

Make sure to replace "input.jpg" with the path to your input image file. The thumbnails and smaller versions of the images will be saved as "thumbnail.jpg" and "small.jpg" respectively.