PDF.co Web API – PDF To Image API – VB.NET – Convert PDF To PNG From URL Asynchronously

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ByteScoutWebApiExample.sln

      

Microsoft Visual Studio Solution File, Format Version 12.00
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ByteScoutWebApiExample.vbproj

      
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    <StartupObject>ByteScoutWebApiExample.Module1</StartupObject>
    <RootNamespace>ByteScoutWebApiExample</RootNamespace>
    <AssemblyName>ByteScoutWebApiExample</AssemblyName>
    <FileAlignment>512</FileAlignment>
    <MyType>Console</MyType>
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Module1.vb

      
Imports System.IO
Imports System.Net
Imports System.Threading
Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq


' Cloud API asynchronous "PDF To PNG" job example.
' Allows to avoid timeout errors when processing huge or scanned PDF documents.

Module Module1

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

	' Source PDF file
	Const SourceFileUrl As String = "https://bytescout-com.s3.amazonaws.com/files/demo-files/cloud-api/pdf-to-image/sample.pdf"
	' Comma-separated list of page indices (or ranges) to process. Leave empty for all pages. Example: '0,2-5,7-'.
	Const Pages As String = ""
	' PDF document password. Leave empty for unprotected documents.
	Const Password As String = ""
	' (!) Make asynchronous job
	Const Async As Boolean = True


	Sub Main()

		' Create standard .NET web client instance
		Dim webClient As WebClient = New WebClient()

		' Set API Key
		webClient.Headers.Add("x-api-key", API_KEY)

        ' Set JSON content type
        webClient.Headers.Add("Content-Type", "application/json")

		' Prepare URL for `PDF To PNG` API call
		Dim url As String = "https://api.pdf.co/v1/pdf/convert/to/png"

        ' Prepare requests params as JSON
        ' See documentation: https : //apidocs.pdf.co
        Dim parameters As New Dictionary(Of String, Object)
		parameters.Add("password", Password)
		parameters.Add("pages", Pages)
		parameters.Add("url", SourceFileUrl)
		parameters.Add("async", Async)

        ' Convert dictionary of params to JSON
        Dim jsonPayload As String = JsonConvert.SerializeObject(parameters)

		Try
			' Execute POST request with JSON payload
			Dim response As String = webClient.UploadString(url, jsonPayload)

			' Parse JSON response
			Dim json As JObject = JObject.Parse(response)

			If json("error").ToObject(Of Boolean) = False Then

				' Asynchronous job ID
				Dim jobId As String = json("jobId").ToString()
				' URL of generated JSON file available after the job completion; it will contain URLs of result PNG files.
				Dim resultJsonFileUrl As String = json("url").ToString()

				' Check the job status in a loop. 
				' If you don't want to pause the main thread you can rework the code 
				' to use a separate thread for the status checking and completion.
				Do
					Dim status As String = CheckJobStatus(jobId) ' Possible statuses: "working", "failed", "aborted", "success".

					' Display timestamp and status (for demo purposes)
					Console.WriteLine(DateTime.Now.ToLongTimeString() + ": " + status)

					If status = "success" Then

						' Download JSON file as string
						Dim jsonFileString As String = webClient.DownloadString(resultJsonFileUrl)

						Dim resultFilesUrls As JArray = JArray.Parse(jsonFileString)

						' Download generated PNG files
						Dim page As Integer = 1
						For Each token As JToken In resultFilesUrls

							Dim resultFileUrl As String = token.ToString()
							Dim localFileName As String = String.Format(".\page{0}.png", page)

							webClient.DownloadFile(resultFileUrl, localFileName)

							Console.WriteLine("Downloaded ""{0}"".", localFileName)
							page = page + 1

						Next

						Exit Do

					ElseIf status = "working" Then

						' Pause for a few seconds
						Thread.Sleep(3000)

					Else

						Console.WriteLine(status)
						Exit Do

					End If

				Loop

			Else
				Console.WriteLine(json("message").ToString())
			End If

		Catch ex As WebException
			Console.WriteLine(ex.ToString())
		End Try

		webClient.Dispose()


		Console.WriteLine()
		Console.WriteLine("Press any key...")
		Console.ReadKey()

	End Sub

	Function CheckJobStatus(jobId As String) As String

		Using webClient As WebClient = New WebClient()

			' Set API Key
			webClient.Headers.Add("x-api-key", API_KEY)

			Dim url As String = "https://api.pdf.co/v1/job/check?jobid=" + jobId

			Dim response As String = webClient.DownloadString(url)
			Dim json As JObject = JObject.Parse(response)

			Return Convert.ToString(json("status"))

		End Using

	End Function

End Module

    

packages.config

      
<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="Newtonsoft.Json" version="10.0.3" targetFramework="net40" />
</packages>
    

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