Bug 503438

Summary:	Transition PGM images (default ones) produce artifacts.
Product:	[Applications] kdenlive	Reporter:	Gabriel Gazzán <gabcorreo>
Component:	Video Effects & Transitions	Assignee:	Jean-Baptiste Mardelle <jb>
Status:	REPORTED ---
Severity:	normal
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	Other
OS:	Other
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	wipe showing artifacts wipe clean (using newly generated image) new wipe image used for testing small artifacts usgin the new image Softness

Description Gabriel Gazzán 2025-04-27 18:09:33 UTC

I've noticed that the PGM wipe images provided with Kdenlive have something bad in them that produces artifacts that can be seen as a noise and an horizontal pattern showed at the edges of the transitions. It happens to all of them at several degrees of magnitude.

I've tried to quickly regenerate one of them (symmetric clock) as a test, using Krita, to see if the problem was in the images themselves or it was something in the code. 
Fortunately, the results with the new image was good, so there must be something in the images themselves that is causing this problem.

Here I attach 3 images:
- result with current "Symmetric clock" wipe.
- result with new "Symmetric clock" wipe. 
- the new "Symmetric clock" image, itself. (it's only a draft to prove the point, it doesn't accurately replicates the original one)

(I've tested it both with HD and SD versions of the images, and both produce the same artifacts)

Comment 1 Gabriel Gazzán 2025-04-27 18:10:09 UTC

Created attachment 180709 [details]
wipe showing artifacts

Comment 2 Gabriel Gazzán 2025-04-27 18:11:04 UTC

Created attachment 180710 [details]
wipe clean (using newly generated image)

Comment 3 Gabriel Gazzán 2025-04-27 18:12:28 UTC

Created attachment 180711 [details]
new wipe image used for testing

Comment 4 Gabriel Gazzán 2025-04-27 18:21:14 UTC

Additional note:
Results with the new image is not without its little imperfections too, at the edges. (attached a 4th image showing those).
I even tried using an 16-bit PNG and it made no difference...
I guess this could, in fact, be something in the code (related to antialiasing of the edges, perhaps?)

Nevertheless, this problem is still much less noticeable than the one generated by the images themselves.

Comment 5 Gabriel Gazzán 2025-04-27 18:22:16 UTC

Created attachment 180712 [details]
small artifacts usgin the new image

Comment 6 Gabriel Gazzán 2025-04-27 20:07:54 UTC

Also related, while not the same issue:

I notice the "Softness" is achieved by just letting the previous frames of the wipe be seen, with various degrees of opacity.
Perhaps a certain degree of blur there, could lead to better results (and a solution to the aliasing of the edges too).

Comment 7 Gabriel Gazzán 2025-04-27 20:11:32 UTC

Created attachment 180713 [details]
Softness