Re: Image transformations

[Alan Third]

On Fri, Jun 14, 2019 at 04:55:39PM +0100, Richard Copley wrote:
> 
> I like the idea Yuri described. It's as powerful and easier to use.
> As far as I can see there would still be a homogeneous matrix on the
> implementation side, though, with the accompanying variations for
> each platform, so perhaps it doesn't overcome your reservations.

FWIW I like Yuri’s suggestion too, but even though it provides a
simple API for doing transforms, and could even replace the transform
code in image.c almost entirely (including for ImageMagick) while
still providing some level of backwards compatibility, it introduces
some other questions.

For example how would we handle cropping? With the code in Emacs at
the moment I cheated: I just reset the origin, and set the width and
height; the rest of the image is still there, we just don’t display
it. If we allow arbitrary translations and rotations after the crop,
however, then it’s reasonable for the user to expect the cropped area
to translate and rotate, without reintroducing areas previously
cropped out. I don’t know how to get round this without, perhaps,
modifying the mask, which isn’t supported on NS at least, or drawing
the image to a new surface at the moment of cropping. I want to avoid
that if possible, but it may be the only solution.

-- 
Alan Third