Patent ID: 8643663

Claim:
A computer implemented method of determining a radial gradient blend defined by a gradient function, the method comprising: identifying respective first and second radial limits for a point of the radial gradient blend, the respective first and second radial limits having known blend values; receiving an estimated value of the gradient function for the point; determining a direction from the estimated value to an ideal value, wherein the ideal value is a value of the gradient function for the point and the direction of the ideal value is determined based on a sign of a decision variable associated with the estimated value; modifying the estimated value by a predetermined amount until the ideal value is within a predetermined threshold of the modified estimated value, a direction of the modified estimated value corresponding to, the direction of the ideal value, wherein the step of determining the modified estimated value of the gradient function comprises: defining a decision variable indicative of a difference between the received estimated value, or a subsequent modified estimate value, and the ideal value of the gradient function, in one or more steps, refining a current estimated value, by: evaluating the decision variable for two estimated values, one of the estimated values being greater than the current estimated value by a first predetermined amount, and the other estimated value being smaller than the current estimated value by a second predetermined amount, determining the signs of the decision variable for each of the two estimated Values, and depending on the determined signs, effecting one of the following: incrementing the current estimated value by a third predetermined amount, or decrementing the current estimated value by a fourth predetermined amount, or maintaining the current estimated value unchanged, the unchanged value in a given step determining the modified estimated value of the gradient function; and determining and storing in the computer a resultant blend value for the point by modifying one of the known blend values of the respective first and second radial limits on the basis of the modified estimated value.