photo editing – Why does GIMP increase the size of exported JPEG files?

I’m using GIMP to edit some vacation pictures (JPEG files) taken with a rather old digital camera. Lacking a professional background, I just went about by trial and error and ended up adjusting the following parameters:

  • Images are way too dark —> Colors > Levels > Input Levels > Increase Clamp Input, decrease High Input
  • Colors could be more vibrant —> Colors > Auto > Color Enhance

When exporting the edited files, I noticed that the file size has increased by a factor of 3, i.e. files less than 3 MB in size are now 10 MB or larger. What is causing this and is there any way to prevent this without trading away image quality?

GIMP: Why can I set a higher quality than original image in the “Export Image as JPEG” dialog?

After having read the GIMP Export Image as JPEG section, I still have one understanding issue:

Why am I able to select a higher quality value than the one from original image in the export dialog?

For example, given a .jpeg image, the quality slider is first set to the default 90. When marking “Use quality settings from original image”, the value is set to 75. I can now still select slider values > 75, which creates the impression to raise the quality above original image.

With that assumption in mind (which may be wrong, I am happy to be corrected here), this dialog does not make sense to me. JPEG is a lossy format and an image with lower quality cannot be magically transformed to a higher-detail image. Also, the value seems to indicate some kind of “absolute quality”, not a relative one – otherwise the original quality would be 100.

GIMP: Why can I save a JPEG with higher quality than original image?

After having read the GIMP Export Image as JPEG section, I still have one understanding issue:

Why am I able to select a higher quality value than the one from original image in the export dialog?

For example, given a .jpeg image, the quality slider is first set to the default 90. When marking “Use quality settings from original image”, the value is set to 75. I can now still select slider values > 75, which creates the impression to raise the quality above original image.

With that assumption in mind (which may be wrong, I am happy to be corrected here), this dialog does not make sense to me. JPEG is a lossy format and an image with lower quality cannot be magically transformed to a higher-detail image. Also, the value seems to indicate some kind of “absolute quality”, not a relative one – otherwise the original quality would be 100.

GiMP ( snap ) and thumbnails for .xcf files

On Ubuntu ( Budgie ) 20.04 when using Gimp as a snap, you’ll see thumbnails for .xcf files only « inside » Gimp and nowhere else ( Nemo, Nautilus, gThumb… )

1⋅ how tell my session to look for thumbnails not only in ~/.cache/thumbnails/ but also in any thumbnails folder inside ~/snap/ ?

2⋅ reading again snap doc I wonder if https://snapcraft.io/docs/thumbnailer-service-interface might be the answer. Should I connect that interface to Gimp ? Or doesn’t it do what I’m looking for ?

I’d prefer an answer to 1⋅ as it may solve the issue for any snap app eventually generating thumbnails.

For references : https://forum.ubuntu-fr.org/viewtopic.php?id=2053949 ⋅ https://forum.snapcraft.io/t/gimp-and-thumbnails-for-xcf-files/18131 ⋅ https://discourse.ubuntubudgie.org/t/gimp-as-a-snap-no-thumbnails-for-xcf-files-in-nemo-gthumb/3799

python – GIMP and github plugin issue

I have Gimp 2.10.14 on my Ubuntu 16.04 (32-bit) installed via flatpak. Since i wanted to make use of re-synthesizer plugin available from https://github.com/bootchk/resynthesizer i downloaded it and saw that gimp didn’t detect the plugins.

So I went over and and installed Gimp from snap and I couldn’t access the plug-in folder from Gimp-preference window refer thread https://askubuntu.com/questions/1249360/snap-app-armor-and-gimp-plugins due to app armor policy but the same issue was noted in it.

I tried various methods mentioned in multiple forums like moving downloaded plug-ins to *config > plug-in folder* to mentioning i.e Edit > Preferences > Folder > plug-ins > add new folder but to no avail

Finally I saw this forum thread https://www.gimp-forum.net/Thread-Gimp-2-10-Resynthesizer-Linux?pid=11261#pid11261 and downloaded the plug-in from the link VOILA!!! it worked (and mentioned it in preference rather than copying it to location)

So i did some detective work and found that the plug-ins downloaded from above link showed up in the terminal as green and the github one showed as plain text screenshots attached
enter image description here

So,

  1. I would like to understand what is the problem here, is it because the plugin is not made for 2.10.14v?

  2. If I need to compile the github download plug-in then how am I supposed to do it ?

  3. How to change app armor policy for snap gimp ?

4.Is it due to older python version (coz firing python in terminal shows 2.7.12v) ?

Postprocessing – How do I apply identical color curves to many images in GIMP?

For everyone else who wanted to do this, I found out.

First I got the desired color curve and clicked the plus sign to save "Save current settings as named preset".

Then I pressed Manage Preferences -> Export Current Settings to File next to the Plus

Then I downloaded CurveBatch from here http://gimpfr.org/contrib_photolabo.php

Then I clicked Edit-> Settings-> Folders-> Plug-Ins in GIMP to find out where Plug-Ins are stored.

I then saved CurveBatch here after extracting it.

Then I had to change the CurveBatch plug-in (photolab_curvebatch) slightly for GIMP 2.10

I have changed

  if lines(0) == "# GIMP curves tool settingsn":

to

  if lines(0) == "# GIMP 'Curves' settingsn":

Since GIMP 2.10 changed the first line indicating that it is a curve file (I don't know why someone would think about doing this for a second and break backwards compatibility for no reason).

Then I hit Filter -> Script-Fu -> Update Scripts

Then I closed and reopened GIMP.

Then the script was now displayed in filters. I hit Filter-> PhotoLab-> Batch Correction-> Curve

I selected the folder where my pictures are located, their extension and the curve file that I exported earlier.

This applied the curves to all of my pictures as I wanted.

apt – GIMP cannot be installed on Ubuntu 18.04.4 LTS

I'm trying to uninstall Gimp but I can't. It also doesn't allow me to install other packages.

Sudo apt-get remove gimp failed

Reading package lists... Done
Building dependency tree       
Reading state information... Done
You might want to run 'apt --fix-broken install' to correct these.
The following packages have unmet dependencies:
 gimp-gmic : Depends: gimp (>= 2.8) but it is not going to be installed
 sane : Depends: libgimp2.0 (>= 2.4.0) but it is not going to be installed
E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).

Other supporting gimp packages. "dpkg –list | grep gimp"

ii  gimp                                                             2.99.1+om~19-0ubu18.04.4~ppa                    amd64        The GNU Image Manipulation Program
ii  gimp-data                                                        2.99.1+om~19-0ubu18.04.4~ppa                    all          Data files for GIMP
ii  gimp-gmic                                                        1:2.4.5+om-ubu18.04.1~gimp299~ppa               amd64        GIMP plugin for GREYC's Magic Image Converter
ii  libgimp3.0                                                       2.99.1+om~19-0ubu18.04.4~ppa                    amd64        Libraries for the GNU Image Manipulation Program

Additional Gimp Details: "apt-cache show gimp"

Package: gimp
Priority: optional
Section: graphics
Installed-Size: 17693
Maintainer: Otto Meier 
Architecture: amd64
Version: 2.99.1+om~19-0ubu18.04.4~ppa
Recommends: ghostscript
Replaces: gimp-plugin-registry
Suggests: gimp-help-en | gimp-help, gimp-data-extras, gvfs-backends, libasound2
Provides: gimp-helpbrowser, gimp-python
Depends: libgimp3.0 (>= 2.99.1+om~19-0ubu18.04.4~ppa), libgimp3.0 (<= 2.99.1+om~19-z), gimp-data (>= 2.99.1+om~19), gimp-data (<= 2.99.1+om~19-z), libgegl-0.4-0 (>> 1:0.4.15+om~0), libbabl-0.1-0 (>> 0.1.63+om~0), liblcms2-2 (>= 2.8), python-gtk2 (>= 2.8.0), libmypaint (>= 1.4.0~7-ubu18.04.3~ppa~c196a86), mypaint-brushes (>= 1.0), gnome-icon-theme, libaa1 (>= 1.4p5), libappstream-glib8 (>= 0.6.7), libbz2-1.0, libc6 (>= 2.27), libcairo-gobject2 (>= 1.10.0), libcairo2 (>= 1.12.0), libfontconfig1 (>= 2.12), libfreetype6 (>= 2.2.1), libgcc1 (>= 1:3.0), libgdk-pixbuf2.0-0 (>= 2.27.1), libgexiv2-2 (>= 0.10.3), libglib2.0-0 (>= 2.55.2), libgs9 (>= 8.61.dfsg.1), libgtk-3-0 (>= 3.21.5), libgudev-1.0-0 (>= 167), libharfbuzz0b (>= 0.6.0), libheif1 (>= 1.1.0), libilmbase12 (>= 2.2.0), libjpeg8 (>= 8c), liblzma5 (>= 5.1.1alpha+20120614), libmng2 (>= 1.0.10), libopenexr22, libopenjp2-7 (>= 2.0.0), libpango-1.0-0 (>= 1.29.4), libpangocairo-1.0-0 (>= 1.29.4), libpangoft2-1.0-0 (>= 1.29.4), libpng16-16 (>= 1.6.2-1), libpoppler-glib8 (>= 0.22.1), librsvg2-2 (>= 2.14.4), libstdc++6 (>= 5.2), libtiff5 (>= 4.0.3), libwebkit2gtk-4.0-37 (>= 2.19.1), libwebp6 (>= 0.5.1), libwebpdemux2 (>= 0.5.1), libwebpmux3 (>= 0.6.1-2), libwmf0.2-7 (>= 0.2.8.4), libx11-6, libxcursor1 (>> 1.1.2), libxext6, libxfixes3, libxmu6, libxpm4, zlib1g (>= 1:1.1.4)
Breaks: gimp-plugin-registry
Filename: pool/main/g/gimp/gimp_2.99.1+om~19-0ubu18.04.4~ppa_amd64.deb
Size: 3978176
MD5sum: 1ed41694e65476e3f2f0e586e9485e8f
SHA1: 25e8a065af5a4a026b3f8519ce8da5cd9ec8e640
SHA256: 8fa5575b12bf3d2218bf88b85aa461018db98b036f7725f08e4ea6feb14804ca
Description-en: The GNU Image Manipulation Program
 GIMP is an advanced picture editor. You can use it to edit, enhance, and
 retouch photos and scans, create drawings, and make your own images.
 It has a large collection of professional-level editing tools and
 filters, similar to the ones you might find in Photoshop. Numerous
 fine-control settings and features like layers, paths, masks, and
 scripting give you total control over your images.
 Many image file formats are supported, including JPEG, Photoshop (.psd),
 and Paint Shop Pro (.psp) files. It can also be used to scan and print
 photos.
 .
 To open files remotely (like over HTTP), install the gvfs-backends
 package.
 .
 To use a MIDI device (like a musical keyboard) as an input controller in GIMP,
 install libasound2 and read the how-to at /usr/share/doc/gimp/README.MIDI
Description-md5: f2effb726861e0d75f53e1793347bcec
Original-Maintainer: Ari Pollak 

Package: gimp
Architecture: amd64
Version: 2.8.22-1
Priority: optional
Section: universe/graphics
Origin: Ubuntu
Maintainer: Ubuntu Developers 
Original-Maintainer: Debian GNOME Maintainers 
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 15398
Provides: gimp-python
Depends: libgimp2.0 (>= 2.8.22), libgimp2.0 (<= 2.8.22-z), gimp-data (>= 2.8.22), gimp-data (<= 2.8.22-z), python-gtk2 (>= 2.8.0), libgdk-pixbuf2.0-0 (>= 2.24.1), libaa1 (>= 1.4p5), libbabl-0.1-0 (>= 0.1.10), libbz2-1.0, libc6 (>= 2.15), libcairo2 (>= 1.10.2), libdbus-1-3 (>= 1.9.14), libdbus-glib-1-2 (>= 0.88), libexif12 (>= 0.6.21-1~), libfontconfig1 (>= 2.12), libfreetype6 (>= 2.2.1), libgegl-0.3-0 (>= 0.3.0), libglib2.0-0 (>= 2.41.1), libgs9 (>= 8.61.dfsg.1), libgtk2.0-0 (>= 2.24.10), libgudev-1.0-0 (>= 167), libjpeg8 (>= 8c), liblcms2-2 (>= 2.2+git20110628), libmng2 (>= 1.0.10), libpango-1.0-0 (>= 1.29.4), libpangocairo-1.0-0 (>= 1.29.4), libpangoft2-1.0-0 (>= 1.29.4), libpng16-16 (>= 1.6.2-1), libpoppler-glib8 (>= 0.18.0), librsvg2-2 (>= 2.14.4), libtiff5 (>= 4.0.3), libwmf0.2-7 (>= 0.2.8.4), libx11-6, libxcursor1 (>> 1.1.2), libxext6, libxfixes3, libxmu6, libxpm4, zlib1g (>= 1:1.1.4), python2.7, python:any (>= 2.7.5-5~)
Recommends: ghostscript
Suggests: gimp-help-en | gimp-help, gimp-data-extras, gvfs-backends, libasound2
Filename: pool/universe/g/gimp/gimp_2.8.22-1_amd64.deb
Size: 3672180
MD5sum: ac5aee938db6979012c945b8f33613d7
SHA1: 9ccb7adb1d967d91cefe52bd99ce23eef76a95be
SHA256: 3cafbc52a67990691ec5102b56c760651d65e8057a3c4b522e1ca93877dfabd7
Homepage: https://www.gimp.org/
Description-en: GNU Image Manipulation Program
 GIMP is an advanced picture editor. You can use it to edit, enhance, and
 retouch photos and scans, create drawings, and make your own images.
 It has a large collection of professional-level editing tools and
 filters, similar to the ones you might find in Photoshop. Numerous
 fine-control settings and features like layers, paths, masks, and
 scripting give you total control over your images.
 .
 Many image file formats are supported, including JPEG, Photoshop (.psd),
 and Paint Shop Pro (.psp) files. It can also be used to scan and print
 photos.
 .
 To open files remotely (like over HTTP), install the gvfs-backends
 package.
 .
 To use a MIDI device (like a musical keyboard) as an input controller in GIMP,
 install libasound2 and read the how-to at /usr/share/doc/gimp/README.MIDI
Description-md5: 0c13253910a0a1bd77c64d38c07351a0
Task: ubuntustudio-publishing, ubuntustudio-photography, ubuntustudio-graphics