Modification of original images by MD

[rxls]

I would like to ask what kind of modifications do the MD reader to the original images. After comparing the same files downloaded from MD in two different occasions I noticed a significant drop in size. Of course no data saver is enabled.

Chapter:
[hidamari] Kemono Michi c21 {source mangadex at 29/03/2019} 42415KB
[hidamari] Kemono Michi c21 {source mangadex at 28/10/2020} 23758KB
Chapter 21 Image 01 File Size: 1546 kB (29/03/2019)
Chapter 21 Image 01 File Size: 832 kB (28/10/2020)

After comparing the images with exiftool I noticed different Color Type & Bit Depth for the same images.

edit
Also some mod please delete Gangking Vol. 7 Ch. 53 since it's corrupted (1page). I've already reported it but no-one has delete it. According to the raws it must me 24 pages

 

[Halo]

@rxls

https://mangadex.org/thread/250545

Holo: Just to add to ix's post - we're currently in the process of pingoing all the .pngs on the image servers. This lossless optimisation process reduces filesize because it strips out the unnecessary metadata and does not result in any loss of quality. This is going to take a while, we're looking at around 16 weeks in total, because there are almost 10TB to go through. By the time it finishes, we expect to save around 1.5 TB of data!

 

[BraveDude8]

@rxls Refer to the announcement linked above, pingo running in lossless .PNG mode will reduce bit depth if it's not being used. diffcheck the actual image files, and there will be no visible difference.

 

[DrWhoCares]

@rxls To further clarify, it's not that there will be "no perceivable difference" but rather that there "is no visual difference."

It is a lossless optimization, it discards unnecessary data chunks and optimizes the rest where possible.