bug#49688: 28.0.50; Attempting to show images crashes Emacs

[Alan Third]

On Sun, Jul 25, 2021 at 12:44:59AM +0200, Rudolf Adamkovič wrote:
> TL;DR The images show pixelated.
> 
> Every modern Mac has a HiDPI (a.k.a. Retina) screen, where each point
> (logical pixel) maps to 4 physical pixels, a.k.a. 2× scale. I in the
> attached small screenshot, please compare the sharpness of the image with
> the text next to it. Emacs renders the image at 1× and the text at 2×.

Without knowing more about the image and how it's being displayed I
can't say whether there's anything wrong with that.

Images are, by default, displayed at 1x resolution so they will appear
the same size on retina and non-retina screens.

If you want to display images with pixels at a 1:1 ratio you need to
scale the image by (/ 1 (frame-scale-factor)), but that will only
work on Emacs 28.

This is how Emacs has always worked on retina screens, this patch
shouldn't change that. If it does then there's something else wrong,
but I don't see any change in image display here.

-- 
Alan Third