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IDProjectCategoryView StatusLast Update
0012518ScribusGraphics / Image Framespublic2014-10-24 23:00
ReporterKunda Assigned To 
PrioritynormalSeverityfeatureReproducibilityhave not tried
Status newResolutionopen 
Product Version1.5.0svn 
Summary0012518: [PATCH] Port BAlpha auto-contrast.patch
Short version: add auto contrast image effect
Long verison:
This patch adds a new image effect called "Auto contrast".
The default settings for this effect do almost precisely the same thing as GIMP's "auto white balance". Discarding (thus clipping) the top and bottom 0.5% of the pixels, it stretches the red, green, and blue color channels to the full range. This can do magic to enhance photographs, in particular when they're tinted towards a certain color. And it can also do horrible things, depending on the image, so be sure to look at the actual result.
The effect has a few options:
Threshold low and Threshold high: This is the percentage of the image's pixels that are discarded when calculating the range of color values. As mentioned above, the default is 0.5% for both, but this can be adjusted indepently for dark (low) and light (high) values. If, for example, your photo has a large over-exposed area (that you may be cropping away anyway), you'll probably want to increase the high threshold.
Sync colors: If this is checked, then instead of adjusting the color channels independently, the low and high values will be identical for all three color channels (using the lowest low value and the highest high value). This means that there will be no color correction (or distortion); rather this will just increase the image contrast.
Amount: Controls the strenght of the effect from 100% (the default) to 0% (no change at all).
This effect only works on RGB images. Frankly, I've never used CMYK images, and I have now idea how I would treat them for applying this effect. In particular this means that this effect won't do anything when exporting CYMK PDFs unless you also apply the "effects before color management" patch (see its description for the reason).
This is not technically a file format change, however I have not tested how Scribus behaves when a file contains an unknown image effect. Thus opening and/or re-saving a .sla file that contains this effect with an unpatched version of Scribus may have unintended consequences.

Proposed Patch: auto-contrast.patch
Additional InformationBackground:
User BAlpha provides a set of patches for new features in Scribus v1.4 . They live on a Bitbucket repo and are GPL2+ licensed

- Overview of theses features :
- Patches :
- Licence is GPL2+ (as stated in Overview page and
TagsNo tags attached.


child of 0012007 new [MetaBugPatch] Port BAlpha new features to 1.5 so as to merge them with SVN 


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Issue History

Date Modified Username Field Change
2014-07-14 01:44 Kunda New Issue
2014-07-14 01:44 Kunda Issue generated from: 0012517
2014-07-14 01:44 Kunda Relationship added child of 0012007
2014-07-14 02:01 Kunda Description Updated
2014-10-24 23:00 Kunda Patch => Yes
2015-09-17 20:10 Kunda Category Graphics / Image Frames => Graphics/Img Frames
2015-09-17 20:11 Kunda Category Graphics/Img Frames => Graphics / Image Frames