[magick-users] Suggestion to Digital Photo Handling section, part 3

[Anthony Thyssen]

- Tong - on  wrote...
| Hi Anthony,
| 
| On http://www.imagemagick.org/Usage/photos/, in Photo Conversion
| Cookbook section you have two examples on converting photos to
| sketches -- "Childrens Color-In Images" & "Pencil Sketch".
| 
| Before going into these, maybe it is a good idea to first discuss
| convert's built-in -charcoal operator, just to make it a full
| story, because there might be people who don't know of the operator. 
| 

I'll add a link to my own discussion...
  http://www.imagemagick.org/Usage/transform/#charcoal
:-)

But the two methods you mention are not really using charcoal as such.
In that case it is used more as a edge detection method, to generate
disgonal pencil lines.

I have added a new 'photo transform' for charcoal.
   http://www.imagemagick.org/Usage/photos/#charcoal
Give it a day to so for it to appear on the main IM exmaple site.


| Moreover, when I apply the Childrens Color-In Image method to a
| portrait photo, it did not work well.  I know that the Childrens
| Color-In Image method was originated from a long discussion about
| Generating Coloring-In Pages on the IM Users Forum. So I'm
| thinking, let's try another algorithm.
| 
Good, because I am certainly not happy with it!

| What I really like to see in the Photo Conversion Cookbook
| section, is an example for "Simplest Sketch", ie, convert the
| photo to a sketch that has bare minimum lines to represent the  
| original photo. I found a very good algorithm from the gimp
| tutorials section. 
| 
| http://www.gimp.org/tutorials/Sketch_Effect/
| 
No that is a great effect!!!

In fact such an effect of removing unimportant lines may be a good one
for image comparision too!

| To be honest, I was just stunned by how good the effect can be.
| I had been trying to achieve the same result in gimp long time ago
| using my limited understanding/knowledge but failed. Looking at
| how a machine can do in just several simples steps, I have to say I
| was amazed. I think that's a very effective algorithm, but I don't 
| know how to do it in IM. 
| 
Hmmm
  highpass fiter:   -- not sure...  Anyone?
  blur:     -blur 0x7
  invert    -negate
  we need the original  then do a opacity 50% and add..

Command so far...
  convert image.png \( +clone -median 2 -blur 0x7 -negate \) \
          -matte -channel A -evaluate set 50% -compose plus -composite \
          ...

Hmmm our image has some color in it but it is close.  prehaps
I have the point of cloning wrong, or I have the high pass filter wrong
(likely)

Continuing  increase contrast
    -sigmoidal-contrast 7x50%
or  -normalize  prehaps with a controled 'denormalize' or greying...
   http://www.imagemagick.org/Usage/color/#greying

After that is simular to using various stech and edge detection.

Of course some manual (sic) handling was also done.

Anyone like to improve this?

-------------------------

Another technique I would like to see converted to IM is....

Watercolors from photos...
   http://www.state-of-entropy.com/watercolor.html

Though the title image is great looking, the example image used is not so
good.

  Anthony Thyssen ( System Programmer )    <A.Thyssen at griffith.edu.au>
 -----------------------------------------------------------------------------
  "I have a top secret gravely important assignment here."
  "What other kind do I ever get?"     -- Stainless Steel Rat (Revenge)
 -----------------------------------------------------------------------------
     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/