Stroke stray pixels

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mediacentral
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Stroke stray pixels

Post by mediacentral »

I've seen in some denied clearart/logo comments an instruction to "add a stroke" to find semi-transparent pixels, seemingly a simple task. I'd like to get in the habit of doing these types of checks (stray pixels, adjusting levels, edge checking) to reduce my 'simple fix denials', however, I can't seem to find a plugin to do this within gimp. So, my question is, what is the procedure of adding a stroke? Is it as simple as Alpha to Selection>Stroke Selection? Will this even do what I'm looking for? Is there a more efficient way of accomplishing this, or a plugin I am unaware of?

I'm a self-taught Gimp-er Googling and learning as I go. I've learned quite a bit since joining Fanart.tv; cruising the forums (Thanks Akovia for the awesome tutorials), looking through denial reasons to get pointers, etc. So I'm sorry if this seems like a no-brainer to some.

As always, thanks for any help.
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akovia
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Re: Stroke stray pixels

Post by akovia »

Maybe I'm missing something, but I've never heard about adding a stroke to find semi-transparent pixels before. Not sure how that would work.
I hardly ever have to deal with finding stray pixels as I render almost everything with the path tool. Even when doing hair, I would trace around it very close with either the path or lasso tool before using any technique to render out the hair.

Just zooming in and looking against the different colored backgrounds should reveal anything you need to fix. One of my favorite ways to remove those almost transparent pixels is to use the curves tool on the alpha channel. I covered this technique in my Gimp From Scratch pt 5 tutorial. Start around the 28 minute mark.

As far as stokes go, I hardly ever get the results I want using stroke selection, unless the selection has perfect edges. I find that stroking it that way only reveals edge imperfections. Your results may vary.
By far the best way to add a stoke is by using the path tool. It's called "Paint Along Path" in your paths tab. This tool allows you to stroke with mitered or rounded corners, dotted or dashed lines, or stroke using any paint brush. (and much more) It's a superior tool but of course you need to have a path to use it.

I am kinda curious how adding a stroke will reveal semi-transparent pixels though. :)
Let me know if you need help with anything.
mediacentral
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Re: Stroke stray pixels

Post by mediacentral »

hey buddy, u miss some small spots ;) little tip - add a stroke after u are finish and u will see every old pixel zombie u forget ;)
^^From a reason for denial on a HD ClearART by schimi2k on 5/31/14.

And I believe I've seen him suggest it other than that single instance. From reading thru the forum, I've deduced that schimi uses photoshop(?). So I assumed this was a photoshop tool, but was wondering if there was an equivalent in gimp.

I have just recently started rendering using the path tool thanks to your 'From Scratch' tuts. Much easier, and a much nicer finished product, than masking, painting and erasing, like I was before. Somehow I missed the part on the alpha channel curves technique. I'll have to go back and review.

I was aware of the stroke path tool, again, from your tutorials. I was just going for the quickest & easiest way I could think of to replicate the advice from schimi.

As you said, using the paths tool should remove any possibility for stray pixels, but I like to do my due diligence to ensure I don't waste the mods' time denying art for simple fixes I can quickly check for on my own.
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schimi2k
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Re: Stroke stray pixels

Post by schimi2k »

Hello mediacentral :)
well i give that tip from time to time, thats correct, and its a fast and simple "technique" to check finaly if u have some Ghost-pixels left ( i call it zombiepixels, cause i like zombies more than ghosts hehe ;) )
let me show it with an example ( i dont know why i choose this clearart but it will work 8-) )
I use a realy EXTREME Example !!! just to show u what i mean with "ADD A STROKE"

Image
http://i.imgur.com/ZeONm7i.png


Thats what u see without any STROKE ... well i dont see anythink i would deny...

now add a Stroke to it... in Photoshop its a "LAYER EFFECT" - dont realy know how to add a layereffect in Gimp - in PS just double click on the right side of the layer in layerpanel and choose "stroke" and add an maybe 2-3pixel Stroke ( outside of course )

u will see THAT - its the SAME IMAGE as before !!!!

Image
http://i.imgur.com/RoRKeEH.png

i make some circles on the black backround where u can see the "Ghost/Zombie" Pixels ! as i say before - this is an EXTREME Example, but when u work on an image for an hour or so u missed such small things on borders or so.
When u work with the pentool to cut out objects from the backround u dont realy need to check it this way ( but it wont hurt ) - When u just "rubber" the backround away, or work with masks its a fast and good technique to see if u have some old pixels left :)

i hope i could show with this example what i mean - maybe akovia can show u how to add a stroke in GIMP
have a nice day :geek:
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akovia
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Re: Stroke stray pixels

Post by akovia »

Great post schimi!
It makes perfect sense now. I love to learn new things. :)
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Re: Stroke stray pixels

Post by schimi2k »

realy ... ok one more... Santa Clause isnt real ;)
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akovia
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Re: Stroke stray pixels

Post by akovia »

That's just MEAN! :(
mediacentral
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Re: Stroke stray pixels

Post by mediacentral »

Thanks schimi, that is kind of what I figured you meant.

Thanks for the pictures and the detailed info.
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