Fit
Controls how the image is fitted to its target dimensions. Below are a couple of examples. Some of these values are based on the object-fit CSS property.
Inside &fit=inside
Default. Preserving aspect ratio, resize the image to be as large as possible while ensuring its dimensions are less than or equal to both those specified.
<img src="//t.net.co/?url=t.net.co/lichtenstein.jpg&w=300&h=300&fit=inside">

Outside &fit=outside
Preserving aspect ratio, resize the image to be as small as possible while ensuring its dimensions are greater than or equal to both those specified.
<img src="//t.net.co/?url=t.net.co/lichtenstein.jpg&w=300&h=300&fit=outside">

Cover &fit=cover
Crop the image to cover both provided dimensions.
<img src="//t.net.co/?url=t.net.co/lichtenstein.jpg&w=300&h=300&fit=cover">

Fill &fit=fill
Ignore the aspect ratio of the input and stretch to both provided dimensions.
<img src="//t.net.co/?url=t.net.co/lichtenstein.jpg&w=300&h=300&fit=fill">

Contain &fit=contain
Embed within both provided dimensions. The remaining space can be filled with a background color by using &cbg=
. See here for the supported color formats.
More info: Issue #80 - letterbox images that need to fit.
<img src="//t.net.co/?url=t.net.co/lichtenstein.jpg&w=300&h=300&fit=contain&cbg=black">

Without enlargement &we
Do not enlarge if the width or height are already less than the specified dimensions.
<img src="//t.net.co/?url=t.net.co/lichtenstein.jpg&w=300&h=300&fit=inside&we">
