So the comment I propose mixing what you said with my understanding: I'm an abstract class which introduce a filter between a drawing request and the final output, handled by #mapColor:
For each potential pixel operation like: source -> op -> output it introducing a color mapping stage: source -> op -> mapping -> output Then #mapColor: can be redefined in subclasses to implement more specific behavior. For example: - ShadowDrawingCanvas will replace the rendered color with the color of shadow (if not transparent). - AlphaBlendingCanvas will add or intensify alpha of rendered color. For an easy to understand example see #drawPolygon:color:borderWidth:borderColor: ShadowDrawingCanvas: see ColorMappingCanvas comment. AlphaBlendingCanvas: see ColorMappingCanvas comment. Laurent. On Mon, Feb 14, 2011 at 7:57 PM, Igor Stasenko <[email protected]> wrote: > On 14 February 2011 18:45, laurent laffont <[email protected]> > wrote: > > Today: ColorMappingCanvas > > > > As far as i understood, this class is abstract, and its subclasses > implement more specific behavior > - shadow > - semitransparency mapping > > > The idea of is kind of canvas is to modify/filter the final output in > rendering pipe.. > i.e., for each potential pixel operation like: > > source -> op -> output > > it introducing a color mapping stage: > > source -> op -> mapping -> output > > > So, then for instance you could make a subclass which could turn all > colors to be grayscale (disregarding that initial input was in > colors). > > in fact i think this guy took wrong direction. It is much more > effective to let the canvas to draw whatever it wants to some > backup/temporary surface, and once it done, simply blit + color-map > result to destination form using one, single strike. > > > -- > Best regards, > Igor Stasenko AKA sig. > >
