On Tue, 11 Mar 2003 09:46:49 +0000 "Adam D. Moss" <adam@xxxxxxxx> wrote: > The idea > of rehash-on-dirty would be to catch identical tiles, even > accidentally-identical tiles (like great masses of transparent > tiles, presuming that you scrub the RGB data of a transparent > pixel; the row-hints stuff has been doing this and potentially > breaking the ill-advised anti-erase feature for 100 years now > and no-one has complained) Perhaps because no-one knew, you should not have told us this. I think that the user should be able to edit the alpha channel independent from the other channels. I don't think that it is unreasonable that a user initially makes some parts of the layer transparent, then makes some other edits to the layer and finally decides that the transparency boundaries should be slightly different, e.g. slightly more feathered. In most cases this will work fine but when some of the tiles have been scrubbed this will not work for these tiles. In my mental model the alpha information is simply one of the "color" channels, that are all completely independent from one another. What I find particularly nasty is that scrubbing could happen at unexpected moments and this makes it very difficult to reproduce any bugs that are related to this "feature". If it is really desirable to remove color information from transparent pixels, this must have a predictable behavior. The logical place seems to be the operations that modify the alpha channel, e.g. erase. These operations should set the color channels to 0 for transparent pixels. In this way you get at least reproducable behavior. Finally, when everybody believes that scrubbing by the tile manager is a great idea, I have another one: delete all tiles from the image that are completely obscured by higher layers. After all, like the color information in transparent pixels, these tiles do not contribute anything to the final image, so it seems very reasonable delete them. Also I suggest that a good random number generator is used to decide when these tiles are deleted :) greetings, Ernst Lippe
