Pseudogrey Script-fu in need of an update.

I originally posted this topic at GIMPChat. Hope Pat sees this post and has the time to possibly update it so it can work in GIMP 2.10x. :slight_smile:

If you want a specific person to see something use the @ plus their handle, like @patdavid. :stuck_out_tongue:

It’d be helpful if you linked directly to the script!

Ack! I didn’t have any time to update that script for 2.10, but honestly - it’s in G’MIC so I’ve left it alone mostly:

If I get a moment I’ll have a look at the old script and see if I can quickly get it sorted out.

1 Like

Forgot that G’MIC now handles that, Pat. I do agree with you as well, Mica, but I had a hunch Pat would see this post. lol

:slight_smile:

Rich (at GIMPChat) actually had updated your script for 2.9 and it works in 2.10, Pat. Always like more than one way to skin a cat. lol

:slight_smile:

http://gimpchat.com/viewtopic.php?f=23&t=4245&p=227917#p227916

2 Likes

Do I need to be logged in at gimpchat to see the attachment? I’d love to add it to our pixls.us gimp github repo

Check with @rich2005 that it’s licensed appropriately.

It still belongs to you patdavid :wink:

Looked at the Script-fu and he mentioned your name/site within it, Pat. :slight_smile:

lol

You beat me to it, Rich. :slight_smile:

I meant that you were ok distributing it. (Didn’t know if you wrote your own thing from scratch or not, so wanted to make sure you were in the loop!). :smiley:

I haven’t used pseudo-grey before. In which post-processing contexts is it useful? To me, to_gray, e.g., is closer to how I perceive the tiger:

gmic sp tiger +to_gray +to_pseudogray..

But psuedo has so much more pop to it!

When used correctly you likely won’t notice much of a difference (if at all). Your settings seem like they may be off a bit between gray and pgray.

@David_Tschumperle and I took a look at this a while back and his comparison images were visually indistinguishable for me, though the theory is certainly sound. (bit stealing).

A great article was posted here a few years ago.

Mentioned in this article was some information about Pseudogrey:

Point is that I haven’t found a personal use for it and am curious where people have.

Could be the case. My example uses the default settings of the commands.

Biggest benifit, per the article that I linked above (and by personal experience) is to address sky banding or any solid large areas with ever slight gradients. For normal conversions, 256 levels is more than enough. Banding is an issue. Can also try to address such issues by adding noise (grain) to break up the banding. :slight_smile:

1 Like

Hi there,

My first approach to RT was an pseudo-grey implementation for BW export. @Morgan_Hardwood stepped in of course and asked for the benefits. I only then found out: There are no benefits, especially when saving to JPG with something other than 100% quality. Even If you take the example from the PIXLS (and formerly Pat’s) BW article, convert it to a greyscale PNG, and compare that to the original, you’ll see that only a few pixels (about 2%) are different. All other subtle differences were wiped out by JPG compression.

HTH,
Flössie

2 Likes

Indeed so, Floessie. You have to save using a lossless format otherwise pseudogrey is all but useless. :slight_smile:

I find with some B&W there is benefit but I save jpg’s at 95%. :slight_smile: Being ancient I used to regularly print 20x16 in B&W from 35mm and find digital has problems matching what I know that can do. :wink: When I hear mention of grain I get the impression people must have strange memories or maybe had everything done via the local chemists. Actually I feel that there are reason why film etc could do a better job that a pc screen.

:frowning: Anyway, still no joy with the other version. Looking around on the web it looks like it may be down to scripting changes - NORMAL and others no longer defined. One suggestion was to replace all such with 0 but yet more errors.

So currently just hope some one can sort it out. Not so sure about the version in GMIC maybe because of the sliders and not knowing how these relate to the original version. It looks to be based on channel mixing but I’m only guessing.
John