[digiKam-users] JPEG grows bigger. Why?

[Andrew Goodbody]

Jpeg is a lossy compression format. The size of the file is dependant on 
two things for the most part. The first is what is in the picture and 
the second is what quality it is saved at. Saving at 100% quality 
generally greatly increases the file size. So the increase may be either 
that you are saving it at a higher quality than previously. Or else the 
changes you make are resulting in an image that does not compress so 
well and so a larger file is produced. It may also depend on which code 
is used to implement the compression used in the jpeg image.

So the answer is 'it depends and we cannot tell without detailed 
inspection of both files by someone who can determine what is going on'.

But I suspect the most likely answer is that the original was saved at 
less than 100% quality.

Andrew

On 06/08/2021 21:52, Dmitri Popov wrote:
> Hello,
> 
> Another day, another question from yours truly. Actually, that's something I've noticed long time ago, but I never bothered to ask. Until now.
> 
> When I edit a JPEG file in digiKam, and then save at 100% quality, the result is usually double the size of the original (for example, a ~11MB JPEG file becomes larger than 22MB). Where do the extra megabytes come from?
> 
> Kind regards,
> Dmitri
> ---
> Tōkyō Made - https://tokyoma.de/
>