some explanation please

[brucet]

OK let me first stress that this is not a PL v PSP competition. Rather just me trying to understand how PL works.

A very simple scenario. I have an image. I duplicate the image. So I have two layers. I edit the bottom layer. I go to the top layer. With the free lasso I make a selection. I then go to the eraser and set it to a 1 or 2 intensity. I want to reveal some of the edited bottom layer. Some, not all. Then while the selection/lasso is still active I apply a mild gaussian blur. The intent is to reveal some of the bottom layer but not clearly. Like looking through a dirty window!

Now in PSP this work fine. However in PL it works fine, 'until' I continue with further editing. At some stage the edited lasso/selection' falls to pieces. Not in a consistent manner either. Sometimes it will get very pixelated. Sometimes the gaussian blur will change.

Can you help me understand what PL is doing that changes the selected area when I make further changes during my work?

I know the above is a bit vague but because it is inconsistent I find it difficult to nail down the exact moment things change. For instance sometimes the selection will change hue or saturation.

regards

[brucet]

OK to add a bit more specific information. Anytime I send a layer to an external program the issue is happening. But only if I have used anything but 100% intensity. BUT!! But anywhere I have used the eraser at all in PL will return from an external editor with a very fine line around any erased area. One pixel at a guess. It's almost as though there is a very fine shrinkage in the transfer from the external editor back to PL. Could it be a gamut conflict between programs?

I guess it all comes down to working completely within PL. But then why have an external feature?

regards

[Herbert123]

I do not work with PSP - but when I send a layer with erased areas to Krita, erase some more, and send it back to Photoline (PNG), it all works as expected. No thin lines or shrinkage at all. I also sent the same layer to Photoshop (TIFF), and again no issues.

Might be a problem with PSP?

[Herbert123]

As for the first question, could you perhaps record the screen, and post it? That would make it easier to understand what your are doing, and how.

[Hoogo]

I remember that you had such a problem before, a thread with a car and a line along the cut out parts,but we have not really found a solution.

You already think about something special about the alpha channel that is returned by PSP. Maybe you can post some small before-after files like this here? The browser doesn't show transparency,, but it's there.

[brucet]

Thanks guys. I'm starting to think it's an issue with how each program is handling gamut/bit depth. ie, if I create a subtle gradient with the spray gun in PL and send that layer to PSP all is fine. However when it comes back to PL my fine gradient edges are now harsh transitions. The 'snail trails' are a real mystery though. These also are a result of flipping between PL and PSP. Anywhere I use an eraser in PL comes back from PSP with the fine 'snail trail'. Maybe it's how I have the save function setup in PSP.

The real issue though is me still wanting to use some of my favorite PSP features. I guess I'm being lazy not hurrying up to find out how to use more of PL's features. I guess an external editor feature is nice but expecting it to work 100% of the time is just not realistic.

Still I like to learn. And sometimes that learning process is a distraction.

I'll try to get a few before and after pic uploaded.

regards

[photoken]

What type of image file are you using? TIFF? 16-bit depth?

[bkh]

OK to add a bit more specific information. Anytime I send a layer to an external program the issue is happening. But only if I have used anything but 100% intensity. BUT!! But anywhere I have used the eraser at all in PL will return from an external editor with a very fine line around any erased area. One pixel at a guess. It's almost as though there is a very fine shrinkage in the transfer from the external editor back to PL. Could it be a gamut conflict between programs?

Hard to tell. Might be a problem with pre-multiplied alpha vs. independent alpha, but this is just a guess. Which external editor and what file format do you use?

Can you provide small sample files showing the effect? Save the pld, then use the external editor (making no changes if possible) and save the pld file with the returned layer. You'll have to .zip both to be able to attach them to a forum post.

Cheers

Burkhard.

[Herbert123]

Which version of PSP do you use?

[Herbert123]

Right, I installed PSP X7, and did some more testing. When I use TIFF as the interchange format, things go all wrong in both PSP and in Photoshop CS6: in PSP the alpha channel seems to be expanding (pre-multiplies with white), while in Photoshop it pre-multiplies the mask with black - which introduces black into the anti-aliased transparent edges.

When I use PNG, I have no issues in both apps.

Ergo, both PSP and Photoshop automatically pre-multiply the mattes (alpha channel) of a TIFF. I was already aware of this in Photoshop, which is why I never use Photoshop for this kind of work (this is a decision by the Photoshop dev team - Chris Cox, senior developer actually states 99% of software expects this).

However, this means you cannot prevent this behaviour in Photoshop. Perhaps you can in PSP, but I doubt it.

Basically, this is BAD - bad for compositing.

The solution is to use PNG, which uses transparency as a value, and not an alpha channel, used in TIFF files - and an alpha channel must be "interpreted" and a decision must be made how to treat the matte edges: multiplied with white, black, or unmultiplied (which is possible to do in After Effects and other professional compositing software).

Moral of the story: avoid TIFF.

[Herbert123]

By the way, a number of years ago a heated discussion between Chris Cox and the user community flared up over the topic of how Photoshop pre-multiplies TIFF alpha channels by default. The entire community tried to convince Chris to change this behaviour in Photoshop, but to no avail: even a very well known and respected film/visual effects compositor was derided by Chris for "having it all wrong", and "Photoshop's behaviour is according to the specs".

It was a pretty sad display of total obstinate pig-headed behaviour on the side of the Photoshop developers.

When you must use transparency, your safest workflow is to do this through PNG. PNG will support up to 16bpc, which is more than enough for almost all purposes.

[photoken]

123,

Thanks for the explanation.

FWIW, I had no problem using 16-bit TIF as an interchange format between PL and CorelPhotoPaint (part of my CorelDraw Graphics Suite X5, which is a couple of versions old by now). When the image layer came back into PL, I zoomed in to the soft edges of the erased areas and did not notice any black or white artifacts.

Corel considers PhotoPaint their "Professional" image editor and it has many features/capabilities not available in PSP....

[brucet]

Herbert123 I think you've hit the proverbial nail on the head. I'm using 16bit tiffs and PSPx7. (FWIW my move to PL was due to the many problems being encountered with PSPx8).

Since my last post I tried, as best I could, to replicate my work flow without opening the external editor,PSPx7, with no issues.

So now I'll try the same but with PNG and see what happens.

regards

[brucet]

Ken I have no experience with CorelPhotoPaint so I can't compare it to Corel PaintShopPro.

regards

[photoken]

Since my last post I tried, as best I could, to replicate my work flow without opening the external editor,PSPx7, with no issues.

Just as a side note, if you get some time to do experimenting, it might be interesting to go to
pexels.com
(which provides images with unrestricted CC0 licenses) to find an image similar to the ones you're working with. Then we could all jump in with PL workflow suggestions....