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 Post subject: G'MIC Finger paint Tutorial
PostPosted: Tue Feb 24, 2015 6:46 pm  (#1) 
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Finger paint Tutorial
With G'MIC 1.6.1.0, coming whenever it is ready, a slightly revised Gimp Fingerpaint filter will be going down the slide ways, launching into a Gimp near you. The current 2014/12/11 version migrates to 2015/02/23 or maybe a little higher. No change in the interface, but a slight darkening that has occurred with strong highlights has been minimized, along with some internal parameter tuning: a brighter, lighter Finger paint is in the offing.
I never wrote up a Gimp Chat tutorial for Finger paint as I had done for Hairlocks, last December, so this puts that to right. Everything here will work with the current Finger paint version, and continue to work with the new. You might be less inclined to raise the gamma or otherwise lighten the result of this filter after you take 1.6.1.0 on board, which will have the 2015/02/23 version, or thereabouts.

What is Finger paint?
First, if you have no idea whatsoever about what Finger paint is, it lives in the G'MIC plug-in, so you need the G'MIC plug-in before any of this makes sense. Here's how you can get it (gmic.eu/gimp.shtml). There are also fine people here on Gimp Chat who compile integrated versions of Gimp and G'MIC. One such good person is samj (www.aljacom.com/~gmic/), another is partha, (partha.com). Searching on either of those names will turn up many, many installation related discussions, and both are enormously helpful. Last, but not least, the author and lead developer of G'MIC, ronounours, is here almost daily; look in the G'MIC Discussion area.
If you have the G'MIC plug-in, then Chris Fiedler did one of those nice, wordless video tutorials which always has such charm. It is worth three minutes of your time: Chris Fiedler Fingerpaint Tutorial On YouTube.
Second, there are resources at gmic.eu
  • The Fingerpaint Filter: A brief introduction to the Gimp Fingerpaint filter
  • Fingerpainting: A walk through of the G'MIC code inside the filter, for those who want to hack the G'MIC
    command language straight up: no ice, oh, maybe a little water on the side.
The filter abducts G'MIC's anisotropic smoothing machinery to make a bump map of finger or brush strokes, these based on regions of similar color. It uses a primitive lighting model to furnish basic light and shadows, and specular highlights.
Premise
You want to transform a photograph into a mimic finger painting. Literally. Three dimensional paint hanging off of canvas, with brush strokes casting shadows and shiny highlights.
  1. Pick a Layer. Make it Active. Strong images with contrasting edges are usually the most successful, though low contrast, high key images can work as well. Here is a prime example:
    Image
  2. Observe that the color has slight variation to it. Painters sometimes like to mix colors on canvas, so that no one region is absolutely just one color. There are a bunch of ways to achieve this. One technique, which tends to follow edges and such, harnesses the G'MIC Spectral Filters ► Bandpass filter. See Post Script: Diversifying Color, following.
  3. Choose Filters ►G'MIC. In the middle of the plug-in there is a selection box containing filter groups. Find Artistic and click on the '►' icon to open it ('▼'). scroll down to Finger paint and click on it. The Finger paint dialog box should open.
  4. Paint and Render Detail. You should find two groups of widgets. The widgets clustered under “Paint Detail” let you furnish hints and policy to guide the business of decomposing an image into strokes. “Render Detail” allows you to furnish hints about how the paint itself should appear.
Paint Detail
  1. Finger Size: Ranges from zero to one and defaults to 0.5. Larger values imply fatter fingers with less detail dexterity. Your image will degenerate into paint swirls near values of one.
  2. Keep Detail: Ranges from zero to one and defaults to 0.5. Larger values makes Finger paint more assiduous about finding image edges. Smaller values induce rather random scribbles. Edges orient brush strokes, so if Finger paint can't be arsed to find edges, strokes generally meander all over the place. That may be perfectly fine in some cases, aggravating in others.
  3. Bristle Size: Ranges from zero to one and defaults to zero. By default, Finger paint uses diffusion ellipses with eccentricities very near one. This lends a fine, sable-hair brush appearance to the “paint.” Increasing this number makes the ellipses less eccentric, giving the appearance of fatter, coarser bristles. Near unity, bristles tend to disappear.
  4. Edge Detect Includes Chroma (EDIC): Turn this on if you'd like to organize brush strokes primarily by color; such an image would tend to have very saturated objects on less saturated backgrounds – think of colored festival balloons floating off into an evening sky, It is of indifferent utility if the image is unsaturated; you'd be better off turning it off in those cases.
Render Detail
  1. Light Direction: Ranges from zero to 360° and defaults to 45.° The default value lights up surfaces facing to the northwest; zero degreees lights from the left, 180° lights from the right.
  2. Shadow: Ranges from zero to one and defaults to 0.5. Larger numbers engender darker shadows.
  3. Highlight: Ranges from zero to one and defaults to 0.5. Larger numbers engender brighter highlights but less saturated and darker mid-tones.
  4. Specular: Ranges from zero to 360° and defaults to 45°. Larger numbers might suggest that the paint is glossy.
Resolution Dependence
Grounded on anisotropic smoothing, everything about Finger paint is scale dependent. It operates at pixel scales, and when one pixel grows larger in relation to the overall image, the Finger paint effect increases. Put another way, smaller images produce more dramatic effects.
As a consequence, the plug in preview may not preview all that well. For an accurate preview, I suggest that you set the layer presentation at 100%, then set the plug-in preview scaling so that the size of features in the preview match the same features on the layer. That is, a circle 70 pixels wide in the original layer should appear in the preview also at 70 pixels wide. There is no easy way to fix this.
Examples
  1. Red: Fingerpainted at 350 × 350. Finger size: 0.5 Keep detail: 0.5 Bristle size: 0.01 EDIC: off Light direction: 45 Shadow: 0.1 Highlight: 0.1 Specular: 0.9
    Image Image
  2. Windmill: Fingerpainted at 1024 × 1024, reduced to 400 × 400. Finger size: 0.4, Keep detail: 0.53, Bristle size: 0.05, EDIC: off, Light direction: 135, Shadow: 0.07, Highlight: 0.08, Specular: 0.13:
    Image Image
  3. Camperdown Elm, Prospect Park, Brooklyn:
    1. 1150 × 710, reduced to 400 × 247, not fingerpainted:
      Image
    2. finger painted at 1150 × 710 then reduced to 400 × 247. Finger size: 0.4 Keep detail: 0.3 Bristle size: 0.1 EDIC: on Light direction: 45 Shadow: 0.06 Highlight: 0.5 Specular: 0.9
      Image
    3. Reduced to 400 × 247 then finger painted. Finger size: 0.4, Keep detail: 0.3 Bristle size: 0.1 EDIC: on Light direction: 45 Shadow: 0.06 Highlight: 0.5 Specular: 0.9
      Image
Post Script: Diversifying Color and Geometry
Vector Graphics tend to have large masses that are the same color. The following 400 × 400 greeting has just two colors, a blue-green and a yellow-orange.
Image
The finger painting of this greeting shows absolute, ruler straight, brush strokes. No human being can make those kind of brush strokes (settings: Finger size: 0.5, Keep detail: 0.5 Bristle size: 0.01 EDIC: off Light direction: 45 Shadow: 0.5 Highlight: 0.5 Specular: 0.5 ):
Image
The G'MIC filter, Spectral Filters ►Bandpass, breaks up these monotone masses with variations that are sensitive to the geometry of the image, so that the variations are plausibly from a human hand. That same output may also warp the graphic just a little bit to suggest a hand drawn aspect. In the following, All values are guidelines. Experiment and play with them:
  1. Duplicate the layer to be finger painted. On the duplicate layer, above the original in the layer stack, run the G'MIC Spectral Filters ►Bandpass. (Settings: Low Frequency: 0.08 High Frequency: 0.2 Channel(s): HSV[hue] Value Action: Normalize Preview Type: <whatever you prefer>). Your top layer should look like this:
    Image
    This is your “color variation layer.” Now we are going to make the “Geometry variation layer.”
  2. Duplicate this top layer (you now have three layers) and desaturate it via Colors ►Desaturate. Choose the “Luminosity” radio button and click on 'OK'. Your top “Geometry layer should look something like this:
    Image
    This is your “Geometry variation layer”. Turn its visibility “off” for now – we'll come back to this layer shortly.
  3. Switch the middle “Color variation layer” and set its mode to “Difference” and its opacity to 0.30. Make sure the original, still pristine layer on the bottom is visible ( toggle the leftmost “eye” button to “on”) The composite of the middle and bottom layer should look something like this:
    Image
    Try Grain Merge, Grain Extract, Add, and Subtract modes for other variations. Play with opacity too. When you are done, merge the middle layer down to the bottom layer (Right Mouse Button on middle “Color variation layer” ► “Merge Down”.
  4. Select the now-merged bottom layer. Choose Filters ►Map ► Displace to acquire the “Displace” dialog. Choose both 'X' and 'Y' displacement, set the distortion magnitude to '3.0' and choose the top “Geometry variation layer” as the displacement source. Hit 'OK'; your bottom layer should now look something like this:
    Image
  5. Summon Filters ►G'MIC ► Artistic ► Finger paint and use settings something like: Finger size: 0.40, Keep detail: 0.50 Bristle size: 0.02 EDIC: off Light direction: 160 Shadow: 0.5 Highlight: 0.8 Specular: 0.7. Could be that your results might look like this:
    Image
    This is how my fingers would paint “Hi!”, spastic as I am.
  6. Go on and have fun. Take care.
A PDF file is attached reproducing all the spelling and grammatical errors that are here in this original.


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File comment: Gimp Chat Finger paint Tutorial
fingerpaint_gc.pdf [4.93 MiB]
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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Tue Feb 24, 2015 7:34 pm  (#2) 
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the first 2 attempts failed, on the 3rd attempt it worked
Image

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Tue Feb 24, 2015 11:40 pm  (#3) 
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Cheers grosood :bigthup

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 12:55 am  (#4) 
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the effect on images is excellent
Image

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 2:32 am  (#5) 
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Hi Garry
just a quick heretical attempt

original:
Attachment:
DSCF0724.png
DSCF0724.png [ 2.65 MiB | Viewed 9413 times ]


applying: FingerPaint, then adding vibrancy to the colours, then a little deform:
Attachment:
DSCF0724_Finger+Vibrancy+Random.png
DSCF0724_Finger+Vibrancy+Random.png [ 1.69 MiB | Viewed 9413 times ]


cheers

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 2:47 am  (#6) 
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2nd attempt, playing with parameters:
Attachment:
DSCF0724_Finger+Vibrancy+Random_2.png
DSCF0724_Finger+Vibrancy+Random_2.png [ 1.54 MiB | Viewed 9410 times ]

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 5:07 am  (#7) 
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still playing with FingerPaint + DeformRandom

original:
Attachment:
1980_Dia_1644.jpg
1980_Dia_1644.jpg [ 264.1 KiB | Viewed 9346 times ]


à la Van Gogh:
Attachment:
van-gogh-1.png
van-gogh-1.png [ 2.12 MiB | Viewed 9346 times ]

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 6:03 am  (#8) 
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Thanks Garry for this nice tutorial.

Just a remark about the preview scale : When you define a new G'MIC filter, you can set its default preview zoom factor, which is what you apparently want to do in your case.
You just have to append '(factor)' to the G'MIC preview command, in your case '0' to says you want a 1:1 view :
For instance, this is how it's done for all smoothing filters :

#@gimp Smooth [anisotropic] : gimp_anisotropic_smoothing, gimp_anisotropic_smoothing_preview(0)


So I guess that this problem can be solved quite easily :)

Cheers,
David.


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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 10:05 am  (#9) 
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@Graechen
That font with so many circular sections is a particularly apt choice for Finger paint, which is fond of curves, but not liking corners all that much. And the cat is quite striking. Finger paint may handle fur nicely, or get very confused by it; the 'Keep detail' slider itself can be hypersensitive, with an ideal setting just 0.1 unit away from one that gives a turbulent, incoherent structure. Thank you for experimenting.
@Odinbc
Cheers, too! (clink!)
@dinasset
As always, I enjoy your experimental series, as they always start with the original and one can see the effect unfold. Also, I have an unconscious predilection of choosing certain types of images over another, a containment you don't suffer from, so I always find new things in your experiments.
@ronounours
Thanks for the Google+ boost, and the technical tip! Finger paint was the first Gimp-G'MIC filter that I set out on, and now, seven months later, can see a few opportunities for improvement. Yours, however, was one I overlooked, and an obvious one. But sometimes my nose gets buried in particulars...

Thank you, all.
G.


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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 10:36 am  (#10) 
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Cool tutorial that produces great results. :tyspin for posting it.

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 11:19 am  (#11) 
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Also Garry, I copy/paste a mail I've already sent you, about the Finger Paint filter.
There is one small problem with the split preview mode. If you read me, maybe you can do something to fix this ?

Quote:
I've noticed that your "Finger Paint" filter displays a splited preview, instead of a full one.
Actually, there is one important line missing in the "@#gimp' comments associated to this filter.
Could you then fix it, to get a working preview ?
Here is the fix, you need to add the line :

#@gimp : sep = separator(), Preview type = choice("Full","Forward horizontal","Forward vertical","Backward horizontal","Backward vertical","Duplicate horizontal","Duplicate vertical")

between lines 193 and 194 of your file at http://particularart.com/static/gmictutor.gmic

With that addition, the command '-gtutor_fpaint_preview' will make its job correctly, instead of taking the value of the parameter 'Specular' as the argument of the command '-gimp_split_preview'.

Maybe this fix can apply for other filters too (in your Testing/ folder ?).


Keep well,

David.


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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 3:43 pm  (#12) 
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I already used this filter for texturing one of my digital paintings at the end of last year. It was in G'MIC's "testing" category, and took quite a bit to find. It's actually one of, if not the most impressive filters I've ever seen. Though my intention was not to purely filter my digital painting, as that would have killed a lot of detail that I needed to keep. So I instead filtered my painting with it, -->copied the filtered image, -->undo to regain my original painting, then created a new layer and pasted the filtered one on top of it. After which I experimented with layer modes and set down the opacity to about 30%, as I wanted a lot of the details of the underlying painting visible. It effectively created an oil / acrylic brush texture. This was my result:

Image


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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 6:37 pm  (#13) 
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Superb job on the coke bottle David-C. :bigthup

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Wed Feb 25, 2015 7:05 pm  (#14) 
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I do like the impasto like result you can get with this preset G. :)


Attachments:
impast.jpg
impast.jpg [ 418.25 KiB | Viewed 2518 times ]

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Thu Feb 26, 2015 9:42 am  (#15) 
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@David-C
An American, having sprung into being just at the cusp of mid-twentieth century, Haddon Sundblom has been seared into my visual cortex, probably in more ways than I am aware of (Sundblom illustrated for Coca-Cola from 1932 through 1964 and gave Americans the iconic Santa Claus that most think of when they think of 'Santa Claus' at all). From what I've seen of his originals, he worked fast, was happy to let his brushwork show, and drew his paintings with his brushwork as much as he painted them. That was probably banging around my subconsciousness when I first started fooling around with the filter. You've certainly got the quintessential Sundblom Coke bottle bang-on. Kudos.

I think you've got the right idea in pulling back on Finger paint with a subtle blend. The filter can hit you over the head if you let it. You've got it just enough to leave people wondering if it is digital art or a scan of a (physical) painting.

@Lyle
Of course, you come by with Finger paint hitting people over the head ;) but in a nice way! I think you've had splendid success in having Finger paint latch onto the right edges, giving the illusion that the flower petals were drawn with two or three deft paint strokes - what I had in mind with Sundblom drawing his painting as well as painting it. Finger paint can get demonic and acquire very strange ideas about what constitutes an edge, but with this one you've tamed that very well. Quite apart from Finger paint, I enjoy the color environment; almost everywhere mute and unsaturated but for that splash of hot pink just where it needs to be.

@Ronounours
Odd - haven't seen your mail yet. But grabbed your patch from here during the wee hours and pushed the revision up, and the server is dutifully sending it down now on an -update. Thank you so much for that, and for the general G'MIC playpen!


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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Thu Feb 26, 2015 11:54 am  (#16) 
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Thanks Garry for the fix !


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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Thu Feb 26, 2015 12:37 pm  (#17) 
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Thank you so much for your tutorial. I will try it in some picture. :tyspin :coolthup
Great outcomes above, I like them a lot. :clap

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Sun Mar 01, 2015 9:48 am  (#18) 
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Homage à Garry...

using Finger Painting + Hair Lock

original
Attachment:
DSCF0914.png
DSCF0914.png [ 2.17 MiB | Viewed 2461 times ]


transformed
Attachment:
DSCF0914_FingerPaint+HairLock.png
DSCF0914_FingerPaint+HairLock.png [ 2.65 MiB | Viewed 2461 times ]


painted with a finger and an ... airbrush!

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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Sun Mar 01, 2015 11:59 pm  (#19) 
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@dinasset
Wow. Quite dramatic. Makes me think of a hot day, a pleasure on this dismal first day of March here on the Atlantic seaboard. Been a day of gray skies, freezing rain and snow here in Brooklyn. Apart from the fingerpainting and airbrushing, that seems to be a very pleasant courtyard. I could sit there all afternoon with a good book.

Garry


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 Post subject: Re: G'MIC Finger paint Tutorial
PostPosted: Mon Mar 02, 2015 2:02 am  (#20) 
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Tuscany.
The warmth is a personal add-on, but I wanted to show that Finger Painting and Hair Lock could work well together: an increase in the "bristle" look.

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