Incorrect image height

[Id2ndR]

CSS set ".remark-slide-content img" height with value "42vh !important". This relative size of 42% on Viewport height, with I expect to be 42% oh the "slide" height is not render as it should be.

I'm not sure if it is a browser issue, a remark one or a slides-in-markdown one, so I report in the end-user software. I got the same behavior in Firefox and Chrome.

Test case:

• open a bowser with a slide containing an image
• use developer mode of the browser, to get the actual heigh of the viewport and the image. Compute the ratio on these and compare to 42%
• resize the browser window to half it size in height. Compute again the new ratio and compare.

Expected results: get the 42% ratio in both previous cases.
Actual result: then the browser window is full screen, the ratio is bigger that expected (47% in my case), and a lot smaller with a small window (about 20% with a window height of half the height on my screen).