On Sun, 17 Jan 2010 03:51:26 -0700
Troy Ablan <tab...@gmail.com> wrote:
| Hi folks,
|
| I'm currently trying to composite (add) a series of png images (exported
| from a movie) into a single image, the final image being a virtual "long
| exposure".
|
| The problem is that I need to scale the RGB values linearly toward
| black, so that a composited result will have appropriately-scaled
| levels, such as after this:
|
| for $seq (0..$#$image) {
| $target->Composite(image => $image->[$seq], compose => 'plus');
| }
|
| For the first try, I used $image->Modulate(brightness => 100*(1/$n));
| where $n is the number of images that I'm trying to composite into one.
| This seemed not to reduce the levels equally per channel, as
| Modulate doesn't seem to linearly scale RGB values. The resulting
| images appear oversaturated.
|
| I then discovered +levels in the command line documentation. This
| option seems to be what I need. However, I cannot find a way to map the
| +levels command line option into perl. Am I missing something, or is
| this simply not available?
|
You can simply use 'level' in perl but add a '!' to the geometry string you
pass to it to have it use the 'reversed' form instead.
I designed it this way so that the API interface can be used without change.
See the very first paragraph of
http://www.imagemagick.org/Usage/color/#level_plus
though it should be in the API library documentation of levelImage() as
well.
http://www.imagemagick.org/api/enhance.php#LevelImage
Anthony Thyssen ( System Programmer ) <a.thys...@griffith.edu.au>
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