Relight, a "digital fill-in flash" filter

This post an update about the work I am doing on shadows/highlights compression and tone mapping. It describes a new filter that works as a sort of "digital fill-in flash", that brightens the dark areas of an image while having a minor effect on the highlights.

Here is a preview of the filter in action (original image of the left, "relight" filter on the right with the corresponding tool dialog opened):

(image source: https://discuss.pixls.us/t/playraw-raw-challenge-backlit/1676)

New shadows/highlights and tone-mapping tools

This post is still work in progress!!!

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Introduction

This post describes the new shadows/highlights adjustment tool that I have introduced in PhotoFlow, and gives some implementation details in case someone would like to port the code to some other image editor.

The shadows/highlights adjustment can be split in the following steps:

1. the input pixels are converted from linear RGB to log grayscale, to create a log-luminance (LL) mask:
   LL = log10(lumi(RGB))
2. the LL mask is blurred with a guided filter pyramid (more on this below)
3. the blurred LL mask is tone-mapped with an analytical function that rises the shadows and lowers the highlights (more on this below); an anchor parameter allows to define the splitting point between shadows and highlights regions
4. the input RGB values are linearly scaled by the ratio of the blurred LL mask after/before the tone mapping

CSS image comparison slider test

Drag the black border ↔ pure Css

Credits:Original idea: solipsistaCP

New batch processing options for image export

Image export options, and a corresponding image export dialog, have been implemented in PhotoFlow quite some time ago:

However, until now those options were not yet implemented in the batch processor. While introducing the image export options, I also had to partly change the way command-line parameters are passed to the batch processor.

As usual, up-to-date packages for Linux, MacOS and Windows 64 bits are available from here.

PhotoFlow - EXIF data info panel

I have just introduced a little but useful enhancement in the PhotoFlow gui: a panel showing the EXIF data of the image being edited. Here is an example:

The up-to-date pre-compiled packages are available as usual from GitHub: https://github.com/aferrero2707/PhotoFlow/releases/tag/continuous (you will have to select those created on 2018/10/10 or newer).

Enjoy!

Launch of crowd-funding campaign on Patreon

Dear PhotoFlow enthusiasts,
I have just launched a crowd-funding campaign on Patreon, with the goal of getting some support out of my FLOSS development activities.

Here is the link to the corresponding creator page: https://www.patreon.com/andreaferrero

Apart from the development of PhotoFlow, that you can follow on this blog and on the forum, I am providing AppImage packages and Continuous Integration support for other graphics-related FLOSS projects, namely:

• The GIMP image manipulation program
• The RawTherapee editor
• LuminanceHDR
• HDRMerge
• The Hugin panorama photo stitcher

If you like what I am doing and you find it useful, it would be great if you could consider a little donation. I do not have very ambitious goals regarding the crowd-funding campaign, and I am surely not going to adopt a philosophy of the kind "you only get it if you pay for it!". The work I am doing will continue regardless of the collected money.

Nevertheless, a little financial contribution will certainly help me to justify the spare time I am spending on FLOSS work!

The new "editing mode" for interactive tools

It has been a while since I posted last time... meanwhile I have been silently working on PhotoFlow, adding new tools and improving the usability.

In this post I will explain how interactive tools (those who require mouse interaction in the preview area in order to set their parameters, like the crop tool) are working in the latest development versions.