(06-13-2022, 07:18 AM)Stephen Liu Wrote: Hi all

I'm going to scan about 1,000 photos to digital images.  On testing I found the size of each digital image is about 2.0MB.  

I can compress its size to about half, 1.1MB on GIMP;
File -> Export As -> Select File Type (By Extension)
file type - jpg
-> Export
Export Image as JPEG
Quality --> 85

The final compressed size of the digital image = 1.1MB

Would the compressed image files affect their future use?  I won't print them but use them on digital album, digital slideshow, posting on websites etc.

Please advice.

(06-13-2022, 07:18 AM)Stephen Liu Wrote: Besides I'll further compress and archive all digital files running "gzip"

Thanks

Regards

(06-13-2022, 07:33 AM)PixLab Wrote:

(06-13-2022, 07:18 AM)Stephen Liu Wrote: Hi all

I'm going to scan about 1,000 photos to digital images.  On testing I found the size of each digital image is about 2.0MB.  

I can compress its size to about half, 1.1MB on GIMP;
File -> Export As -> Select File Type (By Extension)
file type - jpg
-> Export
Export Image as JPEG
Quality --> 85

The final compressed size of the digital image = 1.1MB

Would the compressed image files affect their future use?  I won't print them but use them on digital album, digital slideshow, posting on websites etc.

Please advice.

This type of compression, definitively yes, you will never get back information's loss.
JPEG is a lossy format that offers a higher compression rate than PNG in the trade-off for quality ➤ you are trading quality for smaller size with jpg, in other words, smaller a jpg is ➤ less quality from the original it has

(06-13-2022, 07:18 AM)Stephen Liu Wrote: Besides I'll further compress and archive all digital files running "gzip"

Thanks

Regards

This type of compression, no, it's a completely different type of compression https://www.youtube.com/watch?v=Mjab_aZsdxw
I would use 7z to compress instead of gzip, let say it's a personal choice. https://en.wikipedia.org/wiki/7z

(06-13-2022, 11:57 AM)rich2005 Wrote: If the jpeg from your phone camera is anything like mine then the compression setting is 95.  You can check by using  identify -verbose filename.jpg There is a compression value in the listing.

A bit about jpeg, it is a lossy format, even a 99 setting is compressed and lossy. The jpeg compression -> file size curve is not linear. Not much visible loss in quality down to about 80 but can be a good saving in file size Below 50 big drop off in quality, less saving in file size.

You can get an estimate of file size when exporting a jpeg. Enable the "Show preview in image window" 



PNG is a lossless format. Smaller compression = larger file size. 9 is default and best compression. It can govern how fast a large image loads. Smaller compression loads faster. 

There are other formats, TIFF for example, but you are starting with a jpeg, you might as well continue. You will not much space by packing jpeg/png files to an archive, they are already well compressed but 7zip is a good choice.

(06-13-2022, 01:09 PM)PixLab Wrote: Indeed, like said @rich2005 if it's jpg, no need to convert to png, just stay jpg.

If it was me (in theory), I'll just put all original jpg (from your phone) in a directory, right click on the directory then select "create archive", (or "compress" on Ubuntu? OMG 1 week on MX Linux and I don't really remember what's on the right click on Ubuntu-MATE   )
Then another directory for all the post-processed one, and same right click on it "create archive" or "compress", and store those 2 archives on an external drive.

In reality, I don't compress, I just store the full directories of raw/ photos and post processed jpg on external drive, because I can see the thumbnail, and in 10 years from now I know for a fact that I will not be happy about the jpg, then I will re-process some of the raw... or not