> 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:
>
> 1) determine the transformation's parameters
>
> 2) take the bounding box of Q (a rectangle R) and transform it by the
> inverse of T, giving you a quad Q'
>
> 3) use WarpBlt to transform pixels in Q' (should be a superset of your
> form) to R
>
> 4) 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.html
>>
>> -- 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
>
>
_______________________________________________
Beginners mailing list
Beginners@lists.squeakfoundation.orghttp://lists.squeakfoundation.org/mailman/listinfo/beginners