Have you searched the existing issues (both open and closed) in the libjpeg-turbo issue tracker to ensure that this bug report is not a duplicate? #343 seems related, but that issue is closed.

Does this bug report describe one of the two known and unsolvable issues with the JPEG format? I don't think so.

Clear and concise description of the bug:

While rendering a progressive image, block smoothing appears to stop when one pass interrupts another.

Steps to reproduce the bug (using only libjpeg-turbo):

Apologies, I'm not familiar enough with libjpeg-turbo, but I have a browser demo, and I'm assured that part of the issue is in libjpeg-turbo, although there may need to be changes in Chrome and Firefox too.

• Images
• App (unfortunately the app only works in Chrome due to missing primitives in Firefox)

The app will slowly load a given image, stopping at a particular byte. From the set of images provided, here's cat.jpg stopped at 45538 bytes:

In this example, block smoothing isn't working on the luma channel (at least).

Here's ic-pr.jpg, stopped at 47424 bytes:

In this example, block smoothing isn't working on at least one chroma channel (see the stripes on the jumper).

Expected behavior:

The decoding goes from smooth to sharp, rather than switching to blocky.

Additional information:

I can only reproduce this by causing multiple passes, if I simply truncate the file it renders as expected. The app also supports simple truncation (see the dropdown).