How to change font with Golang

Golang is a fast and convenient programming language that has received more and more widespread attention and use in recent years. In basic Golang programming, it is often necessary to change the font of text. This article will introduce how to use Golang to change the font.

The basic steps to change the font are:

1. Download the font
2. Install the font to the computer
3. Use Golang to print and use the font

Step one: Download fonts

There are many ways to download fonts, but the easiest way is to download them online and choose the fonts that meet your needs. After downloading the fonts, we need to move them to the folder of our Golang project.

Step 2: Install fonts to the computer

Font files usually have a .ttf or .otf suffix. Under Windows systems, we can copy these font files to the Fonts of the operating system. folder. Under Mac system, we need to copy the font files to the /Library/Fonts or ~/Library/Fonts folder.

Step 3: Use Golang to print and use fonts

Golang provides a method to output fonts in the console. We can use the Println function in the built-in fmt package in Golang to print the string with changed font. However, it is important to note that we need to use the fonts installed in the second step to print the output.

The sample code is as follows:

package main

import (
    "fmt"
    "golang.org/x/image/font"
    "golang.org/x/image/font/basicfont"
    "golang.org/x/image/font/inconsolata"
    "golang.org/x/image/font/opentype"
    "image"
    "image/color"
    "image/draw"
    "image/png"
    "io/ioutil"
    "os"
)

func main() {
    tempFile, err := downloadFontTemporarily()
    if err != nil {
        fmt.Printf("Failed to download the font: %v", err)
        return
    }
    // Cleanup the temp file.
    defer os.Remove(tempFile.Name())

    fontBytes, err := ioutil.ReadFile(tempFile.Name())
    if err != nil {
        fmt.Printf("Failed to read the font: %v", err)
        return
    }

    // Parse the font, allowing for a variety of font types.
    f, err := opentype.Parse(fontBytes)
    if err != nil {
        fmt.Printf("Failed to parse the font: %v", err)
        return
    }

    const size = 72
    d := &font.Drawer{
        Dst:  draw.NewRGBA(image.Rect(0, 0, 1024, 1024)),
        Src:  image.NewUniform(color.White),
        Face: truetype.NewFace(f, &truetype.Options{Size: size}),
    }
    d.Dot = fixed.Point26_6{
        X: (fixed.I(10)),
        Y: (fixed.I(50)),
    }
    d.DrawString("Hello World!")

    img := d.Dst.(*draw.RGBA)
    png.Encode(os.Stdout, img)
}

func downloadFontTemporarily() (*os.File, error) {
    // Download a font so we can draw it.
    resp, err := http.Get("https://storage.googleapis.com/golang/go1.9beta1.linux-amd64.tar.gz")
    if err != nil {
        return nil, fmt.Errorf("Failed to open source image: %v", err)
    }

    // Write the file to a temporary directory so `font.OpenType` can use it.
    tempFile, err := ioutil.TempFile("", "font.ttf")
    if err != nil {
        return nil, fmt.Errorf("Failed to create temp file: %v", err)
    }

    // Cleanup the temporary file,
    defer os.Remove(tempFile.Name())

    if _, err = io.Copy(tempFile, resp.Body); err != nil {
        return nil, fmt.Errorf("Failed to write font to temp file: %v", err)
    }

    // Seek back to the start of the file so it can be read again later.
    if _, err = tempFile.Seek(0, io.SeekStart); err != nil {
        return nil, fmt.Errorf("Failed to seek to start of temporary file: %v", err)
    }

    return tempFile, nil
}

This is a sample program that prints the "Hello World!" string. It uses the specified font and uses the DrawString function to draw the characters on the picture. , and finally convert the image to PNG format and output it to the standard output.

For different fonts, we can also use the built-in font package or basicfont package in Golang or the golang.org/x/image/font/inconsolata package to draw fonts.

Summary

Through the introduction of this article, we can see that the method of changing fonts in Golang is very simple. Just download the font, install the font, and then use the Println function in Golang to output the specified font. At the same time, by using the built-in font package or basicfont package or golang.org/x/image/font/inconsolata package to draw fonts, we can greatly increase the flexibility and scalability of Golang applications.

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