Represents the "SM" entry of the graphics state parameter dictionary object.

It is an optional entry defined as part of the PDF 1.3 specification.

It contains a double representing a PDF numeric object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 58, page 129.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 57, page 163.

The smoothness tolerance controls the rendering quality of smooth shading operators. It sets the maximum allowable colour error in device colour space when approximating a smooth shade with flat-colour regions.

Lower smoothness values produce more accurate gradients at the cost of more output primitives. A value of 0 requests the device's maximum quality. The value is in the range 0 to 1.