golang pdf convert image-Golang-php.cn

golang pdf convert image

王林

Release： 2023-05-14 20:27:36

Original

2622 people have browsed it

With the advent of the digital age, the use of electronic documents is becoming more and more widespread, and PDF files are widely used in various scenarios, such as academic papers, contract agreements, electronic books, etc. However, in some cases, we need to convert PDF files to image format for subsequent processing or display. This article will introduce how to use Golang to convert PDF files to image format.

In order to realize the function of converting PDF to images, we need to use a third-party library GoPdf. GoPdf is a library for processing PDF files in the Go language. It supports generating and editing PDF files, and also supports converting PDF to image formats. The installation of GoPdf is very simple, just enter the following command in the terminal:

go get github.com/signintech/gopdf/...

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After the installation is complete, we can start writing programs to convert PDF files into images. A sample program is given below:

package main

import (
    "bufio"
    "flag"
    "fmt"
    "github.com/signintech/gopdf"
    "image"
    "image/jpeg"
    "image/png"
    "os"
    "path/filepath"
    "strings"
)

var (
    inputFile        string // 输入的 PDF 文件名
    outputFilePrefix string // 输出的图片文件名前缀
    outputFormat     string // 输出的图片格式
    dpi              int    // 输出图片分辨率（DPI）
)

func main() {
    flag.StringVar(&inputFile, "input", "", "Input PDF filename")
    flag.StringVar(&outputFilePrefix, "prefix", "", "Output image filename prefix")
    flag.StringVar(&outputFormat, "format", "png", "Output image format: png or jpeg")
    flag.IntVar(&dpi, "dpi", 72, "Output image resolution (DPI)")
    flag.Parse()

    if inputFile == "" {
        fmt.Println("Please specify input PDF filename using -input")
        return
    }

    if outputFilePrefix == "" {
        outputFilePrefix = strings.TrimSuffix(inputFile, filepath.Ext(inputFile))
    }

    pdf, err := gopdf.Open(inputFile)
    if err != nil {
        fmt.Println("Failed to open PDF file:", err)
        return
    }
    defer pdf.Close()

    numPages := pdf.GetPageCount()
    if numPages == 0 {
        fmt.Println("PDF file contains no page")
        return
    }

    for i := 1; i <= numPages; i++ {
        page := pdf.GetPage(i)
        if page == nil {
            continue
        }
        defer page.Close()

        img := page.Render(dpi, dpi, nil)
        if img == nil {
            fmt.Println("Failed to render page", i)
            return
        }

        outputFile := fmt.Sprintf("%s_%d.%s", outputFilePrefix, i, outputFormat)
        file, err := os.Create(outputFile)
        if err != nil {
            fmt.Println("Failed to create output file:", err)
            return
        }
        defer file.Close()

        writer := bufio.NewWriter(file)
        if outputFormat == "png" {
            if err := png.Encode(writer, img); err != nil {
                fmt.Println("Failed to encode image:", err)
                return
            }
        } else {
            if err := jpeg.Encode(writer, img, &jpeg.Options{Quality: 95}); err != nil {
                fmt.Println("Failed to encode image:", err)
                return
            }
        }

        fmt.Println("Page", i, "saved to", outputFile)
    }

    fmt.Println("Done")
}

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In this sample program, we specify the input PDF file name through the command line parameter -input, and -prefix specifies the output The image file name prefix, -format specifies the output image format, -dpi specifies the resolution (DPI) of the output image. If -prefix is not specified, the input file name minus the extension is used as the prefix by default. The program first opens the input PDF file and obtains the total number of pages in it. Then iterate through each page, render it as a picture, and save it to the output file. The image format can be PNG or JPEG, which are encoded using image/png and image/jpeg respectively in the Go standard library.

Using the sample program is very simple, just enter the following command in the terminal:

go run pdf2img.go -input input.pdf

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where input.pdf is the name of the PDF file to be converted. If you need to specify the prefix, format or resolution of the output file, you can add the corresponding command line parameters, for example:

go run pdf2img.go -input input.pdf -prefix output -format jpeg -dpi 300

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This will convert input.pdf into a JPEG format image, The resolution is 300 DPI and saved with names such as output_1.jpeg, output_2.jpeg, output_3.jpeg, etc.

To sum up, using GoPdf and image/png and image/jpeg in the Go standard library can easily convert PDF files to image formats , to implement your own PDF processing needs.

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