On March 15, 2010, Tiemo Hollmann TB toolbook at kestner.de wrote:
I am not that familiar with the image manipulating capabilities of rev. I
have a batch of images with a person in front of a blue background.
What I would like to do is to change the blue background against a white
background, so that a printed image has a better contrast. Up to now I
thought that this is a photoshop job, but I am always again surprised what
people do with rev (blending, masking, etc.). Or any externals for Mac and
Win? I don't know if at all it would be possible, to find and select
automatically the "background" (e.g. select always the topleft corner) and
select all of the blue, like photoshops wizard selecting tool with some
tolerance of 10 or 20%, because the RGB isn't that plain over the whole
background.
and
stephen barncard stephenREVOLUTION2 at barncard.com answered:
you mean you want a "magic wand" or "replace color" tool? I don't
think rev
can do that natively. Adobe may even have a patent on it.
I think "to replace a color in an image" is one of the simpler tasks
feasable with Rev (see farther below for the recipes).
There are some on this list that have explored possibilities of image
editing with Rev - and from which I have learned much when I started
myself to experiment with such things. Some of the results and related
image-manipulating tools can be inspected on my website
<http://www.sanke.org/MetaMedia>.
The two "Imagedata Toolkits" from 2006 and 2007 contain more than
hundred filters and other tools to manipulate images. A number of newer
stacks are still in the process of being prepared for public release.
The basic problem with using Rev for image processing is that with
big-sized images the processing speed can be very, very slow. Another
problem are a number of bugs in Rev that led to rather frequent crashes
when I was working on a set of other tools ("Photo Patchworks",
"Gradientology", "Kaleidoscope Tool"), which has substantially delayed
their release - along with the fact that Rev is no longer in the center
of my interests as it has been before.
I have addressed the speed and crash problems on various occasions and
also in my last post to this list of March 9: "Language comparisons:
"Lua" - simpler and faster than RevTalk?" (which you can also get from here:
<http://www.sanke.org/MetaMedia/LanguageComparisonsLua.rtf>)
and in which I announced two other stacks "Exploring Hues" and "Lua
Filters". Both stacks contain "replace" tools, one that I ported from
Lua and others that I had developed earlier on my own.
Concerning Tiemo's question:
I replaced (a range of) colors colors in two images in two different ways:
1. Replacing a color range with a "plain" replace color
2. Replacing a color range while preserving "structures" in the color
area being replaced, for examples the clouds on the blue sky that now
look red like the replaced color of the sky, but remain discernible
inside the new red background.
Two examples for each approach:
<http://www.sanke.org/MetaMedia/Town-original.jpg>
<http://www.sanke.org/MetaMedia/Town-RedBG-plain.jpg>
and
<http://www.sanke.org/MetaMedia/Landscape-original.jpg>
<http://www.sanke.org/MetaMedia/Landscape-RedBG.jpg>
You find the necessary scripts here:
<http://www.sanke.org/MetaMedia/ReplaceScripts.rtf>
The procedures to replace the colors in this case are like here (many
other approaches are of course possible).
- select a color-to-be-replaced by clicking on the image and getting the
"mousecolor" using a script in the image
- define a "range" for that color via an ask dialog
- get the replace color from somewhere; in my case I used a color field
whose background colors I set with RGB sliders - as in the "Color
Chooser" stack.
- finally press the replace button (and repeat that process if necessary
to refine color selection and range).
I also use a movable graphic on top of the image to restrict such
"replace color" (or any other) effects to a specific area of the image.
Kind regards,
Wilhelm Sanke
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