Andrew wrote: > Say I'm importing an image of a person standing in full figure against > a white background. When this image is in front of another larger > image, you can see the white background behind the person. I just want > to make the white background behind the person invisible so it just > looks like the person is standing in front of the other picture.
I can testify that doing this to a real world image is not trivial (and doing it fast, even more so). I used Rev a couple of years ago for an application where members of the public took a photo of themselves in front of a blue screen, and then used a touchscreen to manipulate the photo in various ways (adding different backgrounds, props etc). The project was ultimately a success (and I still get a very entertaining check feed of images, peaking at around 50 a day) but it was a nightmare, and we wrote off a bundle on it. I confidently and naively assumed that I would take an RGB point that was the 'pure' (or at least average) bluescreen colour, construct a sphere around this, and make transparent any pixel with a colour in this space. Then I decide I needed an inner and outer sphere, with a penumbra of transparency falling off from one to the other. Then I tried something else, ... and so it went on. I was partly handicapped by the architects (who decided that they didn't like the standard bluescreen colour, and went for a dark green instead (!) and also ignored everything we told them about lighting for blue screen, and saved money by using the worst possible option. And the speed issue was greatly magnified because although I coded the backend app which took the photo and added transparency in Revolution, I lost the battle to have the frontend app in Revolution as well; it was coded in Director, which proved to be a massive cycle hog. My app which took 10 seconds (which seemed long but acceptable) to process the image when running in the foreground, took four minutes when Director - doing nothing - was active. So that put the pressure on. But the whole experience greatly increased my respect for Photoshop et al! There's no such thing as a flat colour in a real-world photo. And depending on the image source, all sorts of strange colour pixels can turn up in an area which broadly looks like one colour. Depending on your application, I'd say: either allow for a _lot_ of development time; explore the ways in which you can alter the environment (making the source image more helpful is a lot easier than trying to solve the problems afterwards); consider whether you might do better to build on someone else's work, seeing if you could AppleScript Photoshop or a similar app to do this work for you. Possibly all of the above! Ben Rubinstein | Email: [EMAIL PROTECTED] Cognitive Applications Ltd | Phone: +44 (0)1273-821600 http://www.cogapp.com | Fax : +44 (0)1273-728866 _______________________________________________ use-revolution mailing list [EMAIL PROTECTED] http://lists.runrev.com/mailman/listinfo/use-revolution
