JPEGli En-/Decoder

[j7n]

The JPEG-XL team has released a high precision JPEG encoder called "Jpegli" which can produce JPEG files with less banding in gradients that remain compatible with existing decoders. To extract all of the encoded data, a better decoder must be used in the viewer. When opening regular JPEG files, the difference is not significant. It is probably slower, but not extremely so. Higher precision can be realized even in 8-bit sRGB, which IrfanView deals with. I wonder if it could be added to IrfanView without too many extra dependencies, which unfortunately made the XL plugin big and require modern Windows.

On the Git page, there is an exe encoder and decoder that can be used on Windows NT 6.1 and later. It can be integrated into audio encoder front-ends like Frontah for batch processing. They are statically compiled 3MB each.

The encoder also claims to produce slightly smaller files for a given quality, but in this day that is less important.

Examples best judged against a dark background.

gradient_16.png: source image without dithering

gradient_16_direct_irfan.jpg : encoded by IrfanView / jpeg-turbo directly

gradient_16_LI.jpg : encoded by Li (shows banding with mainstream viewers)

gradient_16_LI.png : encoded by Li and decoded by Li to 8-bit (banding disappears)

gradient_16_LI_Ps_dither.png : encoded by Li and decoded by Li to 16-bit, then dithered to 8-bit (best result)

gradient_8_dither_irfan.jpg : Photoshop CS2 noise shaping, overall superior, but larger size

NOTE: Images provided inside a Zip-file because the forum software transcodes them and the difference is lost.

[Bhikkhu Pesala]

Better send this to Irfan Skiljan. He discontinued the RIOT plugin because it was too big, so I somehow doubt if he would include this niche feature.

Let us know what he says.

[Winnie2]

I already send this feature request to Irfan, a few days ago. He rejected my request.
Maybe requests from more people might change his mind. But Jpegli is still under development and not final.
IrfanView can't show Jpeg files with XYB color space in correct colors right now, which can be created by Jpegli.

[Bhikkhu Pesala]

Thanks for the update. I have changed the thread’s status.

[j7n]

Why not XYB colors? It relies on ICC to fix up the colors. It works as expected. But I think using XYB is not a good idea because JPEG's strength is compatibility with existing software. Using an ICC in Irfan increases loading time by 10x. The Lcms plugin is phenomenally slow. So we lose both compat and speed.

In old version of FastStone 5.5 or Photoshop CS2 XYB does not work. I have upgraded ACE.dll from CS3 to solve a banding issue.

It seems that the developers have achieved unbelievable decoupling of brightness and color. I don't understand how it works. I got lost when they started talking about Long, Medium, Short eye cones. The XYB output has subsampling by default, but there is very little smearing. I can see a faint white glow around the text. The blue and red detail is hard for YCbCr subsampling.

I have an important outstanding request about EXR, so I decided it was not the right time to bother him more.

I uploaded as a Zip because the forum software transcodes the image.

512_16_xyb_ss_LI.zip