How to transcode images in golang

In web development, image transcoding is a very common requirement. In Golang, you can transcode images by using the image and image/jpeg packages in the standard library.

In Golang, images can be decoded into standard image objects through image.Decoder, and standard image objects can be encoded into required image formats through image.Encoder, such as JPG, PNG, BMP, etc. . This article takes transcoding a JPEG format image into PNG format as an example.

First, we need to read a picture in JPEG format, which can be achieved through the following code:

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

img, err := jpeg.Decode(file)
if err != nil {
    log.Fatal(err)
}

In the above code, we use os.Open to open a picture named input.jpg The image file will throw an error if it fails to open. Then we use jpeg.Decode to decode the file into an image object img. If the decoding fails, an error will be thrown.

Next, we need to encode the image object into a PNG format picture. We can use the Encoder in the image/png package for encoding, as follows:

out, err := os.Create("output.png")
if err != nil {
    log.Fatal(err)
}
defer out.Close()

err = png.Encode(out, img)
if err != nil {
    log.Fatal(err)
}

In the above code, we use os.Create to create a PNG format image file named output.png. If the creation fails, will throw an error. Then we use png.Encode to encode the image object img into a PNG format image, and write the result to output.png. If the encoding fails, an error will be thrown.

The complete implementation of the above code is as follows:

package main

import (
    "image/jpeg"
    "image/png"
    "log"
    "os"
)

func main() {

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

    img, err := jpeg.Decode(file)
    if err != nil {
        log.Fatal(err)
    }

    out, err := os.Create("output.png")
    if err != nil {
        log.Fatal(err)
    }
    defer out.Close()

    err = png.Encode(out, img)
    if err != nil {
        log.Fatal(err)
    }

    log.Println("Image conversion successful!")

}

By running the above code, a JPEG format image can be transcoded into a PNG format image. It should be noted that we need to handle errors appropriately during the transcoding process, and we need to close the corresponding resources after using the files and image objects.

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