flash - Programatically draw a (drop)shadow -
this goes programming languages.
i use adobe flash as3 , reason boyond post, cannot use built-in dropshadow filters.
i do, however, have bitmap data available, color , alpha values.
so there should way draw own dropshadow filter.... right? existing algorithms should go , check out?
not looking as3 implementation, other example allow me convert code.
usually, dropshadows done so:
- copy bitmap's alpha channel
- blur copied alpha channel (a gaussian blur should fine)
- move copied alpha channel down , right
- use copied alpha channel darken background (that is, multiply background's rgb values inverse value alpha channel; same combining alpha channel all-black bitmap , alpha-blending on background)
- draw original bitmap (also using alpha-blending)
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