iphone - Four point gradient in iOS

Question

I am planing to create a four point gradient, pictured below, by drawing two linear gradients via core graphics and masking between them with a third black and white linear gradient.

Is there a more efficient way to draw a four point gradient using core graphics, or other?

Answer 1

Draw four circles:

Apply radial transparent gradient:

Result:

Notes:

• The gray lines represent the bitmap size.
• The diameter of the circles is twice the bitmap diameter.
• Each circle is centered at one of the bitmap corner.
• Effectively only the center part is drawn.
• The remaining parts are outside the bitmap.