>> 
>> Attached is a first go at this. I can't work out image.el and
>> image-mode.el, so I'll either need a lot more time or someone more
>> familiar with them can have a look.
>> 
>> The basic problem is that image-size returns physical pixels, and we
>> want to calculate logical pixels. I tried a few things and failed
>> miserably. I tried changing image-size to return logical pixels, but
>> that just seemed to make everything worse, and I don't think it's a
>> good idea to lie about the image size.
> 
> I’m not sure what do you want to achieve here. Are you trying to automatically size bitmap images when opening them, so that it is displayed 1:1 to physical pixels? If can do something like this:
> 
> (insert-image (create-image "~/d/Screen Shot 2021-02-09 at 10.11.56 AM.png"
>                            nil nil :scale (/ 1 (frame-scale-factor))))
> 
> And the image inserted is displayed 1:1 to physical pixels. But :scale is not really meant for controlling pixel ratio. Maybe we should add a :pixel-ratio (or :scale-factor) attribute to control the default display size of a bitmap image?

Actually, :pixel-ratio probably isn’t a good idea. I guess we should just let the user decide what they want when inserting an image, and automatically add :scale in image-mode.

Yuan