Bug 388067

Summary: Image Editor preview / apply processes image twice?
Product: [Applications] digikam Reporter: Roger F <roger.foss>
Component: Plugin-Editor-SharpenAssignee: Digikam Developers <digikam-bugs-null>
Status: RESOLVED INTENTIONAL    
Severity: normal CC: caulier.gilles, metzpinguin
Priority: NOR    
Version First Reported In: 5.6.0   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In: 5.8.0
Sentry Crash Report:

Description Roger F 2017-12-20 11:16:20 UTC 
When I use the Enhance / Sharpening filter in the Image Editor, it takes a while for the preview to show the effect of my settings - especially when I use the Estimate Noise option.
When I click OK to apply the filter, digikam runs the sharpening filter again.  I will have to wait again for the estimation and then application.

However, if I dont't change any settings but simply accept what the preview is showing, couldn't digikam just save the image generated for the Preview?
It always feels like I'm applying the filter one time more than required.

I'm asking because to me it seems the Preview takes just as long as the application of the filter, which suggest the Preview doesn't just do the sharpening on a part of the entire picture.

If I'm wrong about this then feel free to close the issue.
Comment 1 caulier.gilles 2017-12-20 11:24:07 UTC 
You are right, and not.

yes the preview is computed against the whole image IF you don't zoom inside.

When you zoom , the preview render only the visible region on the canvas.

In this case, the final render must be computed over whole image at end.

Note : zooming is important to show effects applied on image details. Don't forget also the type of preview generated where only one portion of image will be used.

So, you proposal to not re-compute effect on whole image is only valid if whole image is show on screen, without a specific image portion to render.
Using 100% of image to preview effect with this kind of tool is typically never used in production (sharpening, noise reduction, etc...)

Gilles Caulier
Comment 2 Maik Qualmann 2017-12-26 20:54:38 UTC 
The final render step is also necessary if the user canceled the preview creation and choose OK. I close the bug as WONTFIX.

Maik