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Extending Color Beyond the End of a Gradient

When you create a gradient, you have the option of filling the space beyond the ends of the gradient with a solid color. Quartz uses the color defined at the boundary of the gradient as the fill color. You can extend beyond the start of a gradient, the end of a gradient, or both. You can apply the option to an axial or a radial gradient created using either a CGShading object or a CGGradient object. Each type of object supplies constants you can use to set the extension option, as you’ll see in “Using a CGGradient Object” and “Using a CGShading Object.”

Figure 8-7 shows an axial gradient that extends at both the starting and ending locations. The line in the figure shows the axis of the gradient. As you can see, the fill colors correspond to the colors at the starting and ending points.

Figure 8-8 compares a radial gradient that does not use the extension options with one that uses extension options for both the starting and ending locations. Quartz takes the starting and ending color values and uses those solid colors to extend the surface as shown. The figure shows the starting and ending circles, and the axis of the gradient.

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