How to Flatten Layers in PDF Files in .NET with C#

Why Use Flatten Layers with C#?

The pdfRest Flatten Layers API Tool is designed to simplify PDFs by merging layers into a single layer, which can be useful in various scenarios such as ensuring compatibility with older PDF viewers, reducing file size, or preparing a document for printing.

This tutorial will guide you through the process of sending an API call to Flatten Layers using C#. For example, a graphic designer might use Flatten Layers to ensure that a complex brochure with multiple layers prints correctly without any layering issues.

Flatten Layers with C# Code Example

using System.Text;

using (var httpClient = new HttpClient { BaseAddress = new Uri("https://api.pdfrest.com") })
{
    using (var request = new HttpRequestMessage(HttpMethod.Post, "flattened-layers-pdf"))
    {
        request.Headers.TryAddWithoutValidation("Api-Key", "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx");
        request.Headers.Accept.Add(new("application/json"));
        var multipartContent = new MultipartFormDataContent();

        var byteArray = File.ReadAllBytes("/path/to/file");
        var byteAryContent = new ByteArrayContent(byteArray);
        multipartContent.Add(byteAryContent, "file", "file_name");
        byteAryContent.Headers.TryAddWithoutValidation("Content-Type", "application/pdf");


        request.Content = multipartContent;
        var response = await httpClient.SendAsync(request);

        var apiResult = await response.Content.ReadAsStringAsync();

        Console.WriteLine("API response received.");
        Console.WriteLine(apiResult);
    }
}

Source code reference: GitHub - pdfRest API Samples

Breaking Down the Code

The code snippet above demonstrates how to use C# to call the pdfRest Flatten Layers API. Let's break down what each part of the code is doing:

using (var httpClient = new HttpClient { BaseAddress = new Uri("https://api.pdfrest.com") })

This line initializes a new instance of the HttpClient class with the base address set to the pdfRest API endpoint.

using (var request = new HttpRequestMessage(HttpMethod.Post, "flattened-layers-pdf"))

Here, we're creating a new POST request to the "flattened-layers-pdf" endpoint.

request.Headers.TryAddWithoutValidation("Api-Key", "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx");

This line adds your API key to the request headers. Replace "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" with your actual pdfRest API key.

var multipartContent = new MultipartFormDataContent();

This initializes a new MultipartFormDataContent object, which allows you to send files as part of the request.

var byteArray = File.ReadAllBytes("/path/to/file");
var byteAryContent = new ByteArrayContent(byteArray);
multipartContent.Add(byteAryContent, "file", "file_name");

These lines read the PDF file you want to flatten from the specified path, create a ByteArrayContent with the file's bytes, and add it to the multipart content with the form field name "file" and the filename "file_name".

var response = await httpClient.SendAsync(request);

This line sends the request to the pdfRest API and waits for the response.

var apiResult = await response.Content.ReadAsStringAsync();

Once the response is received, this line reads the content of the response as a string.

Beyond the Tutorial

By following the steps in this tutorial, you've successfully called the pdfRest Flatten Layers API using C#. This allows you to programmatically flatten layers in a PDF document and handle the resulting file as needed. You're encouraged to demo all of the pdfRest API Tools in the API Lab at https://pdfrest.com/apilab/ and refer to the API Reference documentation at https://pdfrest.com/documentation/ for more information.

Note: This is an example of a multipart API call. Code samples using JSON payloads can be found at GitHub - pdfRest API Samples (JSON Payload).