Defines gradient spread methods.
Values:
| IG_VECT_GRADIENT_SPREAD_PAD | Expand the first or last color. |
| IG_VECT_GRADIENT_SPREAD_REFLECT | Repeat the gradient with reflection. |
| IG_VECT_GRADIENT_SPREAD_REPEAT | Repeat the gradient periodically. |
Remarks:
Spread method specifies how the gradient is expanded.