On 10/14/17 21:25, Per Funke wrote:

in the attached image there are two property windows, both from Gimp. The left showing an image before doing a crop in Gwenview, the right after doing a crop WITHOUT removing anything from it. The difference in size is 7.2MB! There is no quality deterioration as far as I can see, both images seem to be exactly the same

1) What has been removed? (Nothing that the eye can detect anyway)

2) When adjusting an image in Gimp (Colors => Curves) and exporting, it grows bigger than the original.

What has been added?

Since I store some 30000 images at home I'd prefer that Gimp exported images as small as the cropped ones from Gwenview, if possible...

Anybody having any thoughts on this?

Attachments aren't supported in this mailing list.

When using JPEG, there are several compression settings that have an influence on the size including (but not only) the "quality" setting. Your camera likely produces JPEGS with high quality (at least 95). Experimentally, if I slightly crop a JPEG in Gwenview, I get (TEST0 is the initial image from my camera, TEST1 is what Gwenview saved):

General Complete name : TEST0.JPG
Format : JPEG
File size : 7.36 MiB

Image
Format : JPEG
Width : 5 472 pixels
Height : 3 648 pixels
Color space : YUV
Chroma subsampling : 4:2:2
Bit depth : 8 bits
Compression mode : Lossy
Stream size : 7.36 MiB (100%)

General Complete name : TEST1.jpg
Format : JPEG
File size : 1.97 MiB

Image
Format : JPEG
Width : 5 460 pixels
Height : 3 648 pixels
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Compression mode : Lossy
Stream size : 1.97 MiB (100%)

So , the result is saved with quality 75, which IMHO is not enough, and the chroma subsampling is more agressive. That could be OK for web publishing,
but not what I would recommend for archival. You may find this OK, because, as your question indicates, you are pretty new to the field, but look closely at the hard edges in your pictures and you'll see the differences.

In Gimp, when you edit and re-export a JPEG, Gimp uses the same quality settings as in the original image, but you can change the setting in the JPEG export dialog and set new defaults. But on the whole, I seldom use quality below 85 and the quartered chroma.

Unfortunately, attachments generally don't work on the GIMP mailing list...

In the meantime, what file format were you exporting to?

-- Stratadrake strata_ranger@hotmail.com
--------------------
Numbers may not lie, but neither do they tell the whole truth.

From: gimp-user-list  on behalf of Per Funke 
Sent: Saturday, October 14, 2017 12:25:19 PM
To: gimp-user-list@gnome.org
Subject: [Gimp-user] image information disappearing

in the attached image there are two property windows, both from Gimp.
The left showing an image before doing a crop in Gwenview, the right after
doing a crop WITHOUT removing anything from it. The difference in size is
7.2MB! There is no quality deterioration as far as I can see, both images
seem to be exactly the same

1) What has been removed? (Nothing that the eye can detect anyway)

2) When adjusting an image in Gimp (Colors => Curves) and exporting, it
grows bigger than the original.

What has been added?

Since I store some 30000 images at home I'd prefer that Gimp exported
images as small as the cropped ones from Gwenview, if possible...

Anybody having any thoughts on this?

Best,
Per Funke
(using ubuntu)