How to Flatten PDF Transparencies with cURL

Learn how to flatten all PDF transparencies with the pdfRest Flatten Transparencies API Tool using cURL
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Why Use Flatten Transparencies with cURL?

The pdfRest Flatten Transparencies API Tool is a powerful feature that allows users to process PDF files by flattening transparent elements within the document. This can be particularly useful when preparing a PDF for printing or ensuring compatibility across different viewing platforms. This tutorial will show how to send an API call to Flatten Transparencies using the command-line tool cURL, which is widely used for transferring data with URLs.

Imagine you have a PDF with complex vector graphics and transparency effects that look great on-screen but cause issues when printed on certain printers. By flattening the transparencies, you can convert these effects into a format that is more printer-friendly, ensuring that the printed document closely matches what is seen on a display. This is just one scenario where flattening transparencies can be crucial for maintaining the quality and consistency of your PDF documents.

Flatten Transparencies with cURL Code Example

curl -X POST "" \
  -H "Accept: application/json" \
  -H "Content-Type: multipart/form-data" \
  -H "Api-Key: xxxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" \
  -F "file=@/path/to/file" \
  -F "output=example_out"

Reference to the provided code: pdfRest API cURL Samples

Breaking Down the Code

The cURL command provided is used to make a POST request to the pdfRest API endpoint for flattening transparencies in a PDF file. Let's break down each part of the command:


This specifies the HTTP method for the request, which is POST in this case, indicating that data will be sent to the server.


This is the URL of the API endpoint that will process the request to flatten transparencies.

-H "Accept: application/json"

This header tells the server that the client expects a response in JSON format.

-H "Content-Type: multipart/form-data"

This header indicates that the data being sent in the request is in multipart form-data format, which is used for uploading files.

-H "Api-Key: xxxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"

This header is used to authenticate the request with your unique API key provided by pdfRest.

-F "file=@/path/to/file"

This form field is used to attach the file that needs to be processed. The '@' symbol indicates that a file is being uploaded, followed by the path to the file on your local system.

-F "output=example_out"

This form field specifies the name of the output file that will be created after the transparencies have been flattened.

Beyond the Tutorial

By following the steps outlined above, you have learned how to use cURL to make an API call to pdfRest's Flatten Transparencies endpoint. This process is essential for preparing PDFs for various use cases where transparency could cause issues, such as printing or viewing on different devices.

Feel free to demo all of the pdfRest API Tools in the API Lab. For more detailed information, refer to the API Reference Guide.

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

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