Convert PGX Image Free

How to Convert Files

Convert PGX JPEG 2000 test images to and from viewable formats in your browser. Processing runs locally on your device.

What a PGX file holds

PGX is a minimal raster format created for JPEG 2000 conformance testing, and it is used by the JPEG 2000 Verification Model. It stores a single component (one channel) of uncompressed sample data, which is why it is often used one file per colour component during codec testing.

A PGX file begins with a short ASCII header starting with the characters PG, followed by the byte order (ML for big-endian or LM for little-endian), whether the samples are signed, and the bit depth, width, and height. After that header comes the raw sample data. The design is deliberately bare so that a codec's output can be compared byte for byte against a reference.

Strengths and limits

PGX's value is precision and simplicity. Because it stores raw, single-component samples with an explicit bit depth and sign, it is ideal for the exact, lossless comparisons that conformance testing demands, including the high bit depths JPEG 2000 supports.

It is not meant for everyday use. It holds only one component per file, has no colour management, and is supported almost exclusively by JPEG 2000 tooling. To view an image built from PGX components you combine them and convert to a normal format such as PNG or TIFF.

History of PGX

PGX was developed in the early 2000s as part of the JPEG 2000 standardization efforts by ISO/IEC. Its creation aimed to provide a straightforward method for testing codec implementations against the JPEG 2000 specification. By focusing on a single-component raster format, PGX streamlined the process of validating color component handling in JPEG 2000 encoders and decoders.

As JPEG 2000 gained traction in various applications, PGX became a crucial tool for developers and researchers. Its simplicity and precision made it widely adopted for conformance and verification testing. Over time, PGX has been integrated into various JPEG 2000 tooling, ensuring its relevance and accessibility for ongoing codec development and testing processes.

Practical Use of PGX

Choose PGX when precise, lossless comparison of single-channel data is required, particularly in JPEG 2000 conformance testing. It is ideal for scenarios where other formats may introduce compression artifacts or complexity. Common workflows include validating encoder outputs against expected results and analyzing single color channels in image processing tasks.

When converting to or from PGX, ensure that the bit depth and sign of the samples are correctly specified. Compatibility with other formats may vary, so check tools for support of PGX. Use dedicated conversion tools that preserve the integrity of the single-component data. Be aware that PGX files do not support multiple channels, which could limit their use in multi-color workflows.

Working with PGX files

You will run into PGX only when testing or developing JPEG 2000 codecs, where reference images are distributed as PGX to allow exact verification of decoder output.

To inspect the content, use JPEG 2000 tooling that understands the single-component layout, then convert the combined result to PNG or TIFF for viewing. Note the byte-order and bit-depth fields in the header, since misreading them corrupts the sample values.