What you want to do is set the PorterDuff mode on a Paint object; you can then use that in any function which takes a Paint as a parameter, and the correct transfer mode will be applied. I've assembled some quite complex imagery in my apps this way.
String On Apr 23, 9:47 pm, "Rob Y." <[email protected]> wrote: > I'm having the same problem. A Paint object treats Color.TRANSPARENT > as 'paint transparently' - i.e. don't paint anything. What you and I > want is something that 'paints transparency' - ie. replace whatever > color is there with transparency. > > I don't see anything in Canvas or Paint that lets you control this > behavior. Pretty silly, since it ought to be easy to implement. > Maybe they could just define a Color.TRANSPARENCY that has this > behavior. But that would be kludgey. You'd have to set aside a > particular ARGB value (0xffffffff?) with that meaning, and wouldn't be > able to use it as a normal ARGB value. > > There is the Canvas.drawColor(color, PorterDuff.Mode). That lets you > control the way the color is combined with the Canvas. But drawColor > is the only function that seems to support this kind of control. So, > I guess if all you wanted to erase was a rectangle, you could set a > clipping rectangle and erase just that. In fact, I think I'm going to > try that (I am just drawing rectangles). The other thing I was going > to try was similar to your 'replace black with transparency' idea. I > think you can do that by running a getPixel loop across the whole > bitmap, and then replacing any black pixels with transparent pixels (0 > should do the trick). Sounds awfully inefficient, but nothing better > seems to be provided. > > If somebody out there knows of a 'right' way to just get a Paint > object to erase to transparency, please speak up before I commit the > above atrocity. > > -- > You received this message because you are subscribed to the Google > Groups "Android Developers" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group > athttp://groups.google.com/group/android-developers?hl=en -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
