Claus Cyrny on wrote...
| Hi,
|
| I'm currently about learning about compositing in IM, but I have
| the impression that there's an error in the respective section in
| 'Usage' <http://www.imagemagick.org/Usage/compose/>:
|
| The example code is:
|
| |convert bgnd_overlaid.png bgnd.png \
| -compose ChangeMask -composite bgnd_removed.png
|
| |
|
| (The example is about two third down the page.)
|
| In the description of 'compose'
| <http://www.imagemagick.org/script/command-line-options.php#compose>,
| there's only the operator `change-mask'
| available (not `ChangeMask').
|
| When I correct this (I have written a small shell script for this), I am
| getting
| the error message
|
| convert: unrecognized compose operator `change-mask'.
|
| What would be the proper syntax here?
|
yes this is an old topic, but I have been away, and thought I'd throw in
my 2 cents... Just as a FYI...
First constant strings like change-mask is case insensitive,
you can use capitals or lowercase, it doesn't matter to IM.
Next any underscores, or hypens in the name are ignored.
As such all these are the same thing to IM
changemask change-mask ChangeMask C_hangemASK
Sometimes IM also have altunatives for a specific string for example in
-channels "Red", and "Cyan" and special handling for "R" actually mean
the same the same thing, include the first image color channel in
operators that make use of channel selection (-negate, -fx, -seperate
etc).
In your case however the error means your IM does not understand that
specfic string. "Change-Mask" Composition was a very recent addition that I
myself made to ImageMagick Composition code, to allow for the creation of a
"-layers 'OptimizeTransparency'" method for GIF animation compression
optimization.
http://imagemagick.org/Usage/anim_opt/#opt_trans
But the composition method was very useful for more general background
removals, so was made public.
To find out what strings your IM understands use the "-list" option,
with the option name that uses that string. For example
convert -list compose
There are quite a number of "-compose" methods that are internal to IM
and not ment for direct external use, via a "-compose" setting. This
includes "dissolve" and "blend" which has to be set via their own
seperate operator options "-dissolve" and "-blend" rather than
"-compose".
Note however that a new 'method' may exist for a few releases before it
is fully operational, or even thought of as no longer 'experimental'.
A case in point is the "-distort" methods which I hope to be adding more
to in the near future.
Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]>
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