Glenn Linderman on wrote...
| Adobe Photoshop has an operation on layers called "screen".
| Experimentally, I have found that duplicating a picture to two identical
| layers, choosing layer mode "screen", and varying selections for opacity
| depending on how dark a picture is, can nicely brighten a picture
| without that "washed out" look that comes from simply choosing the
| "brighten" operation.
|
| Does anyone have a clue how to produce that same effect in ImageMagick?
|
Sounds like 'Screen' Alpha Composition, which can only brighten images
by a negated multiplication technique.
http://www.cit.gu.edu.au/~anthony/graphics/imagick6/compose/#screen
EG try...
composite image.png image.png -compose screen result.png
It is a non-lienar brightening of the image.
Can you give and example of its use?
| Or what exactly "screen" mode is? The help screen for "layer blending
| modes" defines it this way, which may help someone that understands
| graphics transforms to produce the effect in ImageMagick.
|
| Screen Looks at each channels color information and multiplies the
| inverse of the blend and base colors. The result color is always a
| lighter color. Screening with black leaves the color unchanged.
| Screening with white produces white. The effect is similar to projecting
| multiple photographic slides on top of each other.
|
Yeap. that is a highly technical meaning of screen.
Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]>
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