JPEGT

Revision as of 20:45, 27 February 2026

JPEGT and JPEGT+ (JPEG Transparent or JPEG with Transparency) are image formats created by myself. It's the successor of Hemera Photo-Object.

It's just JPEG with transparency, a feature that didn't come out until earlier with JNG and Hemera Photo-Object.

Likewise, it's being used for clip art, logos, photos, you name it.

A new version called JPEGT+ uses JPEG for the mask, which reduces file sizes with somewhat minimal loss in mask quality.

Identification

JPEGT

The file starts with JPGT%% and then 0x31 0x41 0x59 0x26 0x53 0x58 which it's the first 12 BCD encoded digits of pi.

Then the JPEG picture comes in, and the PNG mask comes in. A variation of this is mostly the same, but the PNG mask is deflated with Pako, in this case it starts with CMPR.

That variation is not longer used, and the current version is using the correct formats.

The idea was also used by Hemera Photo-Object, but the signature is not the same, but how it works it's the same.

JPEGT+

The file starts with JPGT%% and then 0x58 0x53 0x26 0x59 0x41 0x31 which it's the first 12 BCD encoded digits of pi, but each byte is in reversed order.

Then the JPEG picture comes in, and the JPEG mask comes in.

Software

• JPEGT encoder, viewer and decoder

It supports PNG files for encoding and JPEGT files for viewing and decoding back to PNG.