Re: Testing native image scaling

[Andy Moreton]

On Wed 27 Mar 2019, Eli Zaretskii wrote:

>> Date: Wed, 27 Mar 2019 11:35:26 +0900
>> From: YAMAMOTO Mitsuharu <address@hidden>
>> Cc: Alan Third <address@hidden>,
>>      address@hidden
>> 
>>   (insert-sliced-image (create-image "splash.png" nil nil :scale 0.5) nil 
>> nil 3 5)
>> 
>> Actually, I suspect this does not work on W32 because the comparison
>> with the original image size is made for s->slice.width (or height)
>> rather than s->img->width (or height) as I just did for cairo code.
>> Could you check it on W32?
>
> 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"?
>
> Thanks.

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.

w32-sliced-image.png
Description: PNG image

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.

    AndyM