UI selected transform question

[Boudewijn Rempt]

On Saturday 19 March 2005 12:23, Casper Boemann wrote:
> I'm fiddling with recoding scaling,rotating and shearing.
>
> Apart from doing it with integer math and multipass algorithms I also want
> to take selections into account.
>
> Regarding selection. The code is easy enough, but how do we let the user
> scale in a GUI manner:
>
> When you have selected a rect in a traditional paint app. it's easy enough
> simply drag the corners.
>

Well... Most traditional paint apps also use a mask for selections only they
hide it better. The basic problem when scaling is, I guess, finding a way to 
have an accurate rectangle around all the selected pixels -- i.e., a precise 
extent. I've been groping for algorithms for that, but I've found nothing 
that I thought good enough.

> But when you have selection that is a bitmap, then how do you present the
> user with an intuitive GUI.

Lay a raster over the precise extent of the selection with handles at the four 
corners and four sides, with a smart mouse movement detector that figures out 
that when you grab a corner and move round, the selection rotatis, but if you 
move the corner in or out, it resizes. I've seen things like that in other 
apps, so it must be possible.

> A simple slider is not good enough because it doesn't offer the fine
> control down to a single pixel as users would want. Think of a scale to 3
> times original size  plus 3 pixels (to eg match a feature in an underlying
> layer).

Add a ctrl or shft modifier for precise movement, coupled with a extent 
coordinates display in the tool widget.

> do you get the problem and any ideas?

Maybe I didn't get the problem completely, but ideas aplenty!

-- 
Boudewijn Rempt 
http://www.valdyas.org/fading/index.cgi
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
Url : http://mail.kde.org/pipermail/kimageshop/attachments/20050319/dea2e744/attachment-0001.pgp