Besides standard/progressive, the 3rd kind of JPEG compression: load by channel?

Question

this question might be an \"Open Question\" and many of you might be eager to close it, but please don\'t. Let me explain.

As we all know, JPEG has two kinds of compress

Answer 1

The image data in a JPEG file can be sliced up in many different ways, and the slices (or "scans" as they're usually called) can be stored in the file in many different orders.

In most JPEG files, the first scan in the file contains all of the image's color components, interleaved together if it is a color image. In a non-progressive JPEG, the file will contain just that one scan. In a progressive JPEG, other scans will follow, each of which may contain one component or multiple components.

But there's nothing that requires it to be done that way. If the first scan in the file does not contain all the color components, we might call such a file "non-interleaved".

Your examples files are non-interleaved, and they are also progressive. Progressive non-interleaved JPEGs seem to be more widely supported than non-progressive non-interleaved JPEGs.

The standard IJG libjpeg software is capable of creating non-interleaved files. Though it's not exactly easy, you can use its cjpeg utility, with the -scans option documented in the wizard.txt file.