The HTML standard is not clear on how CanvasRenderingContext2D.getImageData should handle floating point parameters:

https://html.spec.whatwg.org/multipage/scripting.html#dom-context-2d-getimagedata

This has led to different behavior of browsers when floating point parameters are passed to getImageData. Here is the number of pixels returned by each browser when the given set of parameters is passed to getImageData:

Parameters                   Chrome    Opera     Firefox     IE & Edge
(1, 1, 1, 1)                 1         1         1           1
(1.5, 1.5, 1, 1)             4         4         1           1
(1, 1, 1.5, 1)               2         2         1           2
(1, 1, 1.5, 1.5)             4         4         1           4 
(1.01, 1.01, 1.01, 1.01)     4         4         1           1
(1.5, 1.5, 1.5, 1.5)         4         4         1           1
(1.99, 1.99, 1.99, 1.99)     9         9         1           4 

Safari is not tested. The test script is attached.
 

Deleted: getImageData-floatingPointParameters.html 808 bytes

getImageData-floatingPointParameters.html 808 bytes View Download