PDF.co Web API – PDF To Image API – JavaScript – Convert PDF To PNG From Uploaded File (Node.js)

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app.js

      
/*jshint esversion: 6 */

var https = require("https");
var path = require("path");
var fs = require("fs");

// `request` module is required for file upload.
// Use "npm install request" command to install.
var request = require("request");

// The authentication key (API Key).
// Get your own by registering at https://app.pdf.co/documentation/api
const API_KEY = "***********************************";


// Source PDF file
const SourceFile = "./sample.pdf";
// Comma-separated list of page indices (or ranges) to process. Leave empty for all pages. Example: '0,2-5,7-'.
const Pages = "";
// PDF document password. Leave empty for unprotected documents.
const Password = "";


// 1. RETRIEVE PRESIGNED URL TO UPLOAD FILE.
getPresignedUrl(API_KEY, SourceFile)
    .then(([uploadUrl, uploadedFileUrl]) => {
        // 2. UPLOAD THE FILE TO CLOUD.
        uploadFile(API_KEY, SourceFile, uploadUrl)
            .then(() => {
                // 3. CONVERT UPLOADED PDF FILE TO PNG
                convertPdfToPng(API_KEY, uploadedFileUrl, Password, Pages);
            })
            .catch(e => {
                console.log(e);
            });
    })
    .catch(e => {
        console.log(e);
    });


function getPresignedUrl(apiKey, localFile) {
    return new Promise(resolve => {
        // Prepare request to `Get Presigned URL` API endpoint
        let queryPath = `/v1/file/upload/get-presigned-url?contenttype=application/octet-stream&name=${path.basename(SourceFile)}`;
        let reqOptions = {
            host: "api.pdf.co",
            path: encodeURI(queryPath),
            headers: { "x-api-key": API_KEY }
        };
        // Send request
        https.get(reqOptions, (response) => {
            response.on("data", (d) => {
                let data = JSON.parse(d);
                if (data.error == false) {
                    // Return presigned url we received
                    resolve([data.presignedUrl, data.url]);
                }
                else {
                    // Service reported error
                    console.log("getPresignedUrl(): " + data.message);
                }
            });
        })
            .on("error", (e) => {
                // Request error
                console.log("getPresignedUrl(): " + e);
            });
    });
}

function uploadFile(apiKey, localFile, uploadUrl) {
    return new Promise(resolve => {
        fs.readFile(SourceFile, (err, data) => {
            request({
                method: "PUT",
                url: uploadUrl,
                body: data,
                headers: {
                    "Content-Type": "application/octet-stream"
                }
            }, (err, res, body) => {
                if (!err) {
                    resolve();
                }
                else {
                    console.log("uploadFile() request error: " + e);
                }
            });
        });
    });
}

function convertPdfToPng(apiKey, uploadedFileUrl, password, pages) {
    // Prepare URL for `PDF To PNG` API call
    var queryPath = `/v1/pdf/convert/to/png`;

    // JSON payload for api request
    var jsonPayload = JSON.stringify({
        password: password, pages: pages, url: uploadedFileUrl
    });

    var reqOptions = {
        host: "api.pdf.co",
        method: "POST",
        path: queryPath,
        headers: {
            "x-api-key": apiKey,
            "Content-Type": "application/json",
            "Content-Length": Buffer.byteLength(jsonPayload, 'utf8')
        }
    };
    // Send request
    var postRequest = https.request(reqOptions, (response) => {
        response.on("data", (d) => {
            response.setEncoding("utf8");
            // Parse JSON response
            let data = JSON.parse(d);
            if (data.error == false) {
                // Download generated PNG files
                var page = 1;
                data.urls.forEach((url) => {
                    var localFileName = `./page${page}.png`;
                    var file = fs.createWriteStream(localFileName);
                    https.get(url, (response2) => {
                        response2.pipe(file)
                            .on("close", () => {
                                console.log(`Generated PNG file saved as "${localFileName}" file.`);
                            });
                    });
                    page++;
                }, this);
            }
            else {
                // Service reported error
                console.log("readBarcodes(): " + data.message);
            }
        });
    })
        .on("error", (e) => {
            // Request error
            console.log("readBarcodes(): " + e);
        });
}

// Write request data
postRequest.write(jsonPayload);
postRequest.end();
    

package.json

      
{
  "name": "test",
  "version": "1.0.0",
  "description": "PDF.co",
  "main": "app.js",
  "scripts": {
  },
  "keywords": [
    "pdf.co",
    "web",
    "api",
    "bytescout",
    "api"
  ],
  "author": "ByteScout & PDF.co",
  "license": "ISC",
  "dependencies": {
    "request": "^2.88.2"
  }
}

    

Output

Though this code snippet is self-explanatory and straight-forward, let’s review it briefly. We can logically divide this code snippet into three parts. First, we’re adding library references and gathering all necessary data. Secondly, we’re uploading the input file and getting its public URL. And lastly, we’re using this public URL and processing PDF to PNG conversion.

Initially all references such as https, path, fs as well external reference such as request are loaded. We’re preparing necessary data such as API_KEY which is used for authenticating request at PDF.co server, SourceFile which as name suggests references source file path, Pages which indicates pages which needs to be converted to image format, etc.

In order to upload a file to PDF.co cloud and getting a public URL, we’re first getting pre-signed URL. This pre-signed URL is retrieved by the API endpoint /v1/file/get-presigned-url. This API request returns with two URLs, one for the pre-signed URL (data.presignedUrl) and the other for public URL (data.url). We’re using this pre-signed URL to upload the actual file using the PUT request, logic of which is in uploadFile function. After uploading the file with PUT request completed, the public URL returned by GetPreSignedURL request points to this uploaded file. This URL is temporary and only available for a few hours for security reasons.

The PDF.co API endpoint /v1/pdf/convert/to/png is used to convert PDF pages to PNG image format. In the request we’re passing JSON payload containing the input file URL, pages which needs to be converted, etc. In the request header we’re passing the PDF.co API key named x-api-key, this API key is used for authentication of the PDF.co request. The response contains URLs of PNG images. These PNG image URLs are downloaded and saved locally.

This is how easy to convert PDF pages to PNG image using the PDF.co API endpoint. Practical makes programmer perfect! Please try this program in your machine to get more out of this article. Thank you for reading!

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