Re: Testing native image scaling

[Andy Moreton <andrewjmoreton@gmail.com>]

On Wed 27 Mar 2019, Eli Zaretskii wrote:

>> From: Andy Moreton <andrewjmoreton@gmail.com>
>> Date: Wed, 27 Mar 2019 18:35:09 +0000
>> 
>> > It seems to work, but maybe I don't know what and how to check.  Can
>> > you show what I should expect to see with and without the :scale
>> > attribute, in "emacs -Q"?
>>
>> I would expect a sliced image to be composed of a grid of tiled images
>> instead of a single image, but to have the same visual appearance as the
>> original image. The w32 code does not get this right.
>
> Did insert-sliced-image ever work on Windows, even before scaling was
> added?
>
>> Adding the ":scale 0.5" argument scales down the tiled array of images
>> correctly, but they still contain the same display artifacts as the
>> sliced image without scaling.
>
> Thanks, but I asked for the _correct_ image I need to expect, because
> I want something to compare to if/when I decide to try to fix this.

Sorry - I thought that was clear. The following forms should all produce
the same visual appearance in the buffer:

(insert-image (create-image "splash.png" nil nil :scale 0.5))

(insert-sliced-image (create-image "splash.png" nil nil :scale 0.5)
 nil nil 1 1)

(insert-sliced-image (create-image "splash.png" nil nil :scale 0.5)
 nil nil 3 5)

The sliced images are displayed as an array of tiled smaller images, but
should otherwise have the same appearance as the original (non-sliced)
image.

    AndyM