What is MIME type "image/x-portable-graymap"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

image/x-portable-graymap defines a very simple grayscale image format from the Netpbm suite. This format stores image data as shades of gray without color information.
It uses a minimal header to specify details such as the image’s width, height, and maximum gray value. After the header, the file holds pixel data in either plain text (ASCII) or binary form. This makes it easy to read and process, even with basic tools.

Simplicity: The file structure is straightforward, which aids in manual editing and debugging.
Flexibility: The dual ASCII and binary representations allow for easy human inspection or efficient processing.
Interoperability: It is part of a family of formats used in Netpbm applications. Other related formats include PPM for color images, PGM for portable graymap graphics, PNM for any variation within the family, and PBM for bitmap images.
Practical Use: It is useful in quick image processing, testing algorithms, and converting images between different software systems.

For more technical details and history on the Netpbm formats, visit Netpbm on Wikipedia.
This MIME type serves as a robust, no-frills option when a lightweight, grayscale image format is needed in various computing environments.

Associated file extensions

.ppm, .pgm, .pnm, .pbm

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: image/x-portable-graymap

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="image/x-portable-graymap">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');
    
    http.createServer((req, res) => {
      res.setHeader('Content-Type', 'image/x-portable-graymap');
      res.end('Content here');
    }).listen(3000);

Associated file extensions

.ppm, .pgm, .pnm, .pbm

FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.