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Turn photo to cartoon manually http://gimpchat.com/viewtopic.php?f=23&t=19531	Page 1 of 1

Author:

cli345 [ Wed Aug 04, 2021 11:22 am ]

Post subject:

Turn photo to cartoon manually

Hello,

Here is a very short tutorial about turning a photo into a cartoon picture manually without:

G'MIC "Artistic" filters,
plug-ins (except G'MIC "Repair" filters),
drawing.

(It's just what I learned during my experiments to turn photos into cartoons.)

Warning: It aims to make simple style cartoons (not to make more artistic cartoons).

You can proceed, for example, like this:

Reduce the image to about 700px-1000px wide or high
Duplicate layer
On bottom layer, "Colors -> Saturation (scale=1.8)"
On bottom layer, "Colors -> Hue-Chroma (lightness=10)"
On top layer, "Filters -> G'MIC-Qt -> Repair -> Smooth [NL-Means]"
On top layer, "Filters -> G'MIC-Qt -> Repair -> Smooth [Bilateral]"
On top layer, "Filters -> Edge-Detect -> Difference of Gaussians (legacy)" (uncheck "Invert" option)
On top layer, "Colors -> Desaturate -> Desaturate (mode=Value)"
On top layer, "Colors -> Invert"
On top layer, "Colors -> Threshold : about 210-240, 255"
On top layer, set "layer mode" to "multiply"
On top layer, "Merge down"
"Filters -> G'MIC-Qt -> Repair -> Smooth [Bilateral]", multiple times

The following posts explain the reasons why this method works better (according to me) than :

desaturing first
or using "Filters -> Edge-Detect -> Edge...(Sobel)"

To be continued...

Author:	cli345 [ Thu Aug 05, 2021 6:37 am ]
Post subject:	Re: Turn photo to cartoon manually
1) The big steps Here are the four big steps: Intensify colors, that is: On bottom layer, "Colors -> Saturation (scale=1.8)" On bottom layer, "Colors -> Hue-Chroma (lightness=10)" Stroke edges (the big part), that is: On top layer, "Filters -> G'MIC-Qt -> Repair -> Smooth [NL-Means]" On top layer, "Filters -> G'MIC-Qt -> Repair -> Smooth [Bilateral]" On top layer, "Filters -> Edge-Detect -> Difference of Gaussians (legacy)" (uncheck "Invert" option) On top layer, "Colors -> Desaturate -> Desaturate (mode=Value)" On top layer, "Colors -> Invert" On top layer, "Colors -> Threshold : about 210-240, 255" Mix, that is: On top layer, set "layer mode" to "multiply" On top layer, "Merge down" Flatten, that is just: "Filters -> G'MIC-Qt -> Repair -> Smooth [Bilateral]", multiple times Attachment: steps4.jpg [ 39.26 KiB \| Viewed 4947 times ] The very difficult step is "stroke edges". To be continued...

Author:	Wallace [ Thu Aug 05, 2021 8:56 pm ]
Post subject:	Re: Turn photo to cartoon manually
Thank you cli345 for posting this tutorial. We've added it to our Tutorial Index. Gimp Chat Tutorial Index

Author:

cli345 [ Fri Aug 06, 2021 6:45 am ]

Post subject:

Re: Turn photo to cartoon manually

Thanks, Wallace!

2) The steps to "Stroke edges"

Here are the five steps to "Stroke edges":

Smooth, that is:
- On top layer, "Filters -> G'MIC-Qt -> Repair -> Smooth [NL-Means]"
- On top layer, "Filters -> G'MIC-Qt -> Repair -> Smooth [Bilateral]"
Detect edges, that is just: On top layer, "Filters -> Edge-Detect -> Difference of Gaussians (legacy)" (uncheck "Invert" option)
Desaturate, that is just: On top layer, "Colors -> Desaturate -> Desaturate (mode=Value)"
Invert, that is just: On top layer, "Colors -> Invert"
Increase contrast, that is just: On top layer, "Colors -> Threshold : about 210-240, 255"

Attachment:

stepEdge5.jpg [ 32 KiB | Viewed 4868 times ]

There are three choices to do:

Which smooth (I haven't understood the reason why one smooth works better than another one)
Which edge detection (see following posts)
In which order, to do the steps 2,3,4 (see following posts). There are three possibilities:
- Detect, desaturate, invert
- Detect, invert, desaturate
- Desaturate, detect, invert

To be continued...

Author:

cli345 [ Sat Aug 07, 2021 8:13 am ]

Post subject:

Re: Turn photo to cartoon manually

3) "Detect, desaturate, invert"

To show that "Detect, desaturate, invert" is the best choice (in my view), here are three little experiments on the following image:

Attachment:

multiplColors.jpg [ 4.9 KiB | Viewed 4737 times ]

First experiment ("Desaturate, detect, invert"):

Desaturate the image (you choose the method yourself, try several ones), you can try:
- Colors -> Desaturate -> Desaturate (choose the mode you want)
- Colors -> Desaturate -> Color to Gray
Filters -> Edge-Detect -> Edge
Colors -> Invert

Second experiment ("Detect, invert, desaturate"):

Filters -> Edge-Detect -> Edge
Colors -> Invert
Colors -> Desaturate -> Desaturate (choose the mode you want)

Third experiment ("Detect, desaturate, invert"):

Filters -> Edge-Detect -> Edge
Colors -> Desaturate -> Desaturate (mode=Value) (compare with other modes)
Colors -> Invert

Have fun!

With which experiment do we obtain the edges more easily ?

In the first experiment, the desaturation of the image make you to lose some differences of colors. But, sometimes, limits of objects is visible as a difference of hue.

In the second experiment, some differences of colors is turned into yellow lines. But, it's difficult to find a desaturation method that turns yellow to dark gray.

The third experiment seems (to me) to give the best result. Some difference of colors is turned to blue lines. Only the "value" mode turns these to very light gray.

To be continued...

Author:

cli345 [ Sun Aug 08, 2021 3:24 pm ]

Post subject:

Re: Turn photo to cartoon manually

4) Stroke edges on the darker side

I think it's better to stroke edges on the darker side of edge locations (and not astride edge locations).

To show that, here are two little experiments on the following image:

Attachment:

smoothEye.jpg [ 1.88 KiB | Viewed 4703 times ]

First experiment:

Duplicate Layer
Filters -> Edge-Detect -> Edge (Sobel)
Colors -> Desaturate -> Desaturate (mode=Value)
Colors -> Invert
Colors -> Threshold : 170
Set mode to "multiply"
Toggle the visibility multiple times quickly (to see the effect well) (note the enlargement of dark zones)

Second experiment:

Duplicate Layer
Filters -> Edge-Detect -> Difference of Gaussians (legacy) (Radius1 = 8) (uncheck "Invert" option)
Colors -> Desaturate -> Desaturate (mode=Value)
Colors -> Invert
Colors -> Threshold : 232
Set mode to "multiply"
Toggle the visibility multiple times quickly (to see the effect well)

Have fun!

Which experiment gives the less distorted picture ?

To be continued...

Author:

cli345 [ Mon Aug 09, 2021 10:35 am ]

Post subject:

Re: Turn photo to cartoon manually

Here is the result of the first experiment:

Attachment:

smoothEyeExp1.jpg [ 2.95 KiB | Viewed 4678 times ]

Here is the result of the second experiment:

Attachment:

smoothEyeExp2.jpg [ 2.74 KiB | Viewed 4678 times ]

The difference between the two experiments was the method of edge detection (as implemented in Gimp).

First experiment (Sobel): strokes the edges astride the edge locations
Second experiment (Difference of Gaussians): strokes the edges onto the darker side of the edge locations

Stroking the edges astride enlarges dark zones of the image. This effect distorts the eyes of persons.
So, for "Comic Book" effect, I prefer stroking the edges onto the darker side.

Here are some Gimp (and G'MIC) filters that stroke astride:

Filters -> Edge-Detect -> Edge... (all the algorithms except Laplace),
Filters -> Edge-Detect -> Neon...
Filters -> Edge-Detect -> Sobel...
Filters -> Edge-Detect -> Image Gradient...
Filters -> G'MIC-Qt... -> Contours -> Edges
Filters -> G'MIC-Qt... -> Contours -> Edge
Filters -> G'MIC-Qt... -> Artistic -> Cartoon
Filters -> G'MIC-Qt... -> Artistic -> Poster Edges
Filters -> G'MIC-Qt... -> Testing -> Jayprich -> Jpr Line Edges
Filters -> G'MIC-Qt... -> Testing -> Joan Rake -> Artistic -> Neon
Filters -> G'MIC-Qt... -> Testing -> Joan Rake -> Contours -> Gradient Norm [JR's mod]
Filters -> G'MIC-Qt... -> Testing -> Naggobot -> Smooth Sketch
Filters -> G'MIC-Qt... -> Testing -> PhotoComix -> Color Sketch

Here are some methods that stroke onto the darker side:

Filters -> Edge-Detect -> Edge... (Laplace),
Filters -> Edge-Detect -> Laplace...,
Filters -> Edge-Detect -> Difference of Gaussians... (radius1 greater than radius2),
Filters -> Edge-Detect -> Difference of Gaussians (legacy)... (radius1 greater than radius2),
- Duplicate layer
- On bottom layer, "Filters -> Blur -> Gaussian Blur..."
- On top layer, set "layer mode" to "subtract"
- On top layer, "Merge down"
Filters -> Artistic -> Cartoon...
Filters -> G'MIC-Qt... -> Contours -> Morphological Filter (Action = Dilation - Original, size=2)
Filters -> G'MIC-Qt... -> Artistic -> Comic Book
Colors -> Tone Mapping -> Retinex... (Low, 16, 3, 0.1)

(Exception: For more artistical results, some little distortions can be needed. So, I think, in this case, it's better not to follow this tutorial!)

The tutorial is finished.

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