Hi Iulian,
I'm glad to hear that it worked for you. I wonder why you implemented it in a C DLL... As far as I can see, the manipulations with the parameters would be done only once for every quad you want to transform. The computation time for that should be negligible compared to the time it takes to actually transform all the pixels in the quad / rectangle. At least that's what I was thinking, maybe i am wrong?
Cheers
Matthias
On Tue, Sep 23, 2008 at 1:08 AM, Iulian Wande Radu infinite.flow@gmail.com wrote:
Thank you for the guidelines for skewing forms.
I've followed Matthias' instructions (and the associated math doc) and skewing works well this way through WarpBlt. (The code linked by Yoshiki was too slow and didn't work fully).
I wrote the math conversions in a C DLL, and it would probably be useful for people. Is there any place where I could put the code so the community can use it ?
Cheers, Iulian
---------- Forwarded message ---------- From: Matthias Berth matthias.berth@googlemail.com Date: Tue, Jul 22, 2008 at 7:10 PM Subject: Re: [Newbies] Skewing Forms in Squeak V2 To: "A friendly place to get answers to even the most basic questions about Squeak." beginners@lists.squeakfoundation.org
So it comes down to this:
given a projective transformation T from a rectangle (your form) to a quad Q (what you want to draw on screen), how can you express the same transformation in terms of mapping a quad to a rectangle (what WarpBlt needs)?
One possible plan is:
determine the transformation's parameters
take the bounding box of Q (a rectangle R) and transform it by the
inverse of T, giving you a quad Q'
- use WarpBlt to transform pixels in Q' (should be a superset of your
form) to R
- mask the result with your original quad Q, using pixel-by-pixel
operations on Forms
I think all you need in terms of mathematics for this is in http://www.cs.cmu.edu/~ph/869/www/notes/proj/proj.pdf
Hope this helps, feel free to ask about the details,
Matthias
On Thu, Jul 24, 2008 at 1:39 AM, Yoshiki Ohshima yoshiki@vpri.org wrote:
At Tue, 22 Jul 2008 13:53:21 -0400, Iulian Wande Radu wrote:
Hi, I'd like to skew the graphics of a Form, is there an easy way to do this in v2 ?
What I want is to take the rectangle from a normal form, transform it into an arbitrarily-defined quadrilateral, and then paint on the screen. I saw that WarpBlt does something like this.. but it maps a quadrilateral section of a form onto a rectangle.
There was similar a discussion on this a while ago:
http://lists.squeakfoundation.org/pipermail/squeak-dev/2001-February/013402....
-- Yoshiki _______________________________________________ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners