Proportions constraints and rendering
A proportions constraint defines the intended proportions of an image when rendered.
The original image does not have to match these proportions, but it will automatically be cropped to match them when rendered.
Also, a user will not be able to manually crop an image to any other proportions.
If an image has multiple proportions defined, the user will be able to choose between them when cropping manually.
For additional settings, including free-form cropping and focal points, see the properties of the ProportionsAttribute.
Combined with size constraints
Proportions constraints are often combined with size constraints, for example to ensure an image is of standard 3:2 proportions while maintaining a minimum size of 1200x800 pixels.
In that case, it is enough to specify a minimum width of 1200 pixels, since the proportions constraint of 3:2 effectively makes the minimum height 800 pixels.
When both proportions and size constraints have been defined, a user can only select an image that can be cropped to the specified proportions while maintaining the minimum size.
Render an image with custom proportions
It is possible to override any proportions constraints when rendering an image.
For example, you might decide to use a product image with a proportions constraint of 16:9 and turn it into a small square image to use as a thumbnail in a search result.