How to convert pictures to PDF files using Golang

Golang is an efficient and easy-to-learn programming language. It has developed rapidly in recent years and has won the popularity of more and more developers. This article will introduce you how to use Golang to convert images into PDF files.

I. Before you begin

Before converting images, you need to ensure that the Go language environment and related dependent libraries have been installed on your computer. At the same time, you need to make sure you have the images you need to convert ready.

II. Use Golang library to convert images to PDF

First, we need to install a third-party library to convert images to PDF. Here we will use the gofpdf library to operate. Enter the following code in the terminal to install:

go get -u github.com/jung-kurt/gofpdf

After the installation is completed, we can introduce this library into the code and start converting images. The following is a sample code that can convert multiple JPG format pictures into one PDF file:

package main

import (
    "image/jpeg"
    "os"

    "github.com/jung-kurt/gofpdf"
)

func main() {
    // 创建一个新的pdf文件
    pdf := gofpdf.New("P", "mm", "A4", "")
    // 循环读取需要转换的图片
    for _, file := range []string{"image1.jpg", "image2.jpg", "image3.jpg"} {
        // 利用第三方库读取图片
        imgFile, err := os.Open(file)
        defer imgFile.Close()

        img, err := jpeg.Decode(imgFile)
        if err != nil {
            panic(err)
        }

        // 添加一个新的页面
        pdf.AddPage()

        // 设置图片的大小，使之填满整个页面
        imgWidth := pdf.GetPageSize()[0] - 20.0
        imgHeight := imgWidth * float64(img.Bounds().Dy()) / float64(img.Bounds().Dx())

        // 在pdf页面上绘制图片
        pdf.Image(file, 10.0, 10.0, imgWidth, imgHeight, false, "", 0, "")

    }

    // 输出pdf文件
    err := pdf.OutputFileAndClose("output.pdf")
    if err != nil {
        panic(err)
    }
}

The above code first creates a new pdf file, and then uses a loop to read the picture files that need to be converted. We used the image/jpeg library to read the image, then set the size of the image in the pdf page, and finally used the pdf.Image() method to draw the image on each page. Finally, we use the pdf.OutputFileAndClose() method to output the pdf file.

III. Summary

With the above code, you have successfully used Golang to convert images to PDF files. Due to the efficiency and simplicity of the Golang language, batch conversion of large-scale files has become possible. I hope this article can inspire you and help you develop better.

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