shift / roll color
shift / roll color is a color special effects plug-in for iMovie. it manipulates the color values of each pixel in various, user-configurable ways. the result is a clip with significantly altered colors. the effect ranges from slightly changed colors to totally alien color combinations. the plug-in provides three different methods to change the colors
red, green, blue sliders
depending upon the method chosen (see below), these sliders apply the desired change to the selected channel. the green and blue sliders have no effect when choosing 'roll whole pixel' method.
this menu selects the processing method used to alter the color of a pixel. you can choose between the following methods:
- shift values:
the value of a channel is increased / decreased by the amount of the slider. if a value exceeds the maximum possible for a channel, it is wrapped around.
- strangeroll values:
this rather strange method will employ a modified roll algorithm to generate strange (and compared to a straight roll, smoothed) color effects.
- roll whole pixel
the whole pixel is used to shift/roll the value (note: alpha is ignored, as iMovie doesn't use it). this will create extreme color effects, most of which will make the image unrecognizable. note that only the 'red' slider is used in this method.
- shift value (no wrap)
simply adds/subtracts a constant value from the selected channel. values are clipped to minimum and maximim possible values per channel.
- roll channels (strict)
this method applies a mathematically strict roll algorithm to the pixel. in contrast to our 'strangeroll' method, this one is mathematically correct, but may be visually less pleasing on most settings.
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