使用 Visual Basic 将任何图像转换为 WebP

在本教程中，我们将介绍如何实现图像转换器的异步方法。您只需将源图像发送到 SubmitWebPConversionTask 或任何其他提交 API 方法（如 SubmitBmpConversionTask、SubmitDicomConversionTask 等）即可接收任务标识符作为响应。

收到任务标识符后，您需要通过调用 GetConversionTaskStatus 方法检查任务状态。只要任务状态等于“Waiting”，您需要在几秒钟延迟后调用相同的方法。一旦您从GetConversionTaskStatus方法收到“Completed”，您就可以调用DownloadResult方法来下载最终图像。您可以使用下面的 Visual Basic 实现。

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Imports System
Imports System.IO
Imports System.Net.Http

Module Program
    Async Function SubmitWebPConversionTask(filePathToConvert As String, rapidApiKey As String) As Task(Of String)
        Using httpClient As New HttpClient()
            Using form As New MultipartFormDataContent()

                form.Headers.Add("X-RapidAPI-Key", rapidApiKey)
                form.Add(New StringContent("true"), "lossy")
                Dim fileBytes = Await File.ReadAllBytesAsync(filePathToConvert)
                Dim fileName = Path.GetFileName(filePathToConvert)
                form.Add(New ByteArrayContent(fileBytes, 0, fileBytes.Length), "file", fileName)

                Using response = Await httpClient.PostAsync("https://image-converter4.p.rapidapi.com/submitWebPConversionTask", form)

                    response.EnsureSuccessStatusCode()
                    Return Await response.Content.ReadAsStringAsync()
                End Using
            End Using
        End Using
    End Function
    Async Function GetConversionTaskStatus(taskId As String, rapidApiKey As String) As Task(Of String)
        Using httpClient As New HttpClient()
            httpClient.DefaultRequestHeaders.Add("X-RapidAPI-Key", rapidApiKey)
            Using response = Await httpClient.GetAsync($"https://image-converter4.p.rapidapi.com/getConversionTaskStatus?taskId={taskId}")

                response.EnsureSuccessStatusCode()
                Return Await response.Content.ReadAsStringAsync()
            End Using
        End Using
    End Function
    Async Function DownloadResult(taskId As String, rapidApiKey As String) As Task(Of Byte())
        Using httpClient As New HttpClient()
            httpClient.DefaultRequestHeaders.Add("X-RapidAPI-Key", rapidApiKey)
            Using response = Await httpClient.GetAsync($"https://image-converter4.p.rapidapi.com/downloadResult?taskId={taskId}")

                response.EnsureSuccessStatusCode()
                Return Await response.Content.ReadAsByteArrayAsync()
            End Using
        End Using
    End Function
    Public Async Function ConvertToWebPAsync() As Task
        Dim rapidApiKey = "<YOUR RAPIDAPI KEY HERE>"
        Dim filePathToConvert = "<SOURCE IMAGE FILE TO CONVERT>"
        Dim taskId = Await SubmitWebPConversionTask(filePathToConvert, rapidApiKey)
        Dim retryCount = 0
        Do While (retryCount < 100)
            retryCount += 1
            Await Task.Delay(5000)
            Dim status = Await GetConversionTaskStatus(taskId, rapidApiKey)
            If (status = "Completed") Then
                Dim fileBytes = Await DownloadResult(taskId, rapidApiKey)
                Await File.WriteAllBytesAsync("final_image.webp", fileBytes)
                Exit Do
            ElseIf (status = "Waiting") Then
                Continue Do
            ElseIf (status = "Failed") Then
                Throw New Exception("Cannot convert image")
            Else
                Throw New Exception("Invalid status")
            End If
        Loop
    End Function
    Sub Main(args As String())
        ConvertToWebPAsync().Wait()
    End Sub
End Module