Function

CGContextSetAlpha

Sets the opacity level for objects drawn in a graphics context.

Declaration

void CGContextSetAlpha(CGContextRef c, CGFloat alpha);

Parameters

c

The graphics context for which to set the current graphics state’s alpha value parameter.

alpha

A value that specifies the opacity level. Values can range from 0.0 (transparent) to 1.0 (opaque). Values outside this range are clipped to 0.0 or 1.0.

Discussion

This function sets the alpha value parameter for the specified graphics context. To clear the contents of the drawing canvas, use CGContextClearRect.

See Also

Setting Color, Color Space, and Shadow Values

CGContextSetCMYKFillColor

Sets the current fill color to a value in the DeviceCMYK color space.

CGContextSetFillColor

Sets the current fill color.

CGContextSetCMYKStrokeColor

Sets the current stroke color to a value in the DeviceCMYK color space.

CGContextSetFillColorSpace

Sets the fill color space in a graphics context.

CGContextSetFillColorWithColor

Sets the current fill color in a graphics context, using a CGColor.

CGContextSetGrayFillColor

Sets the current fill color to a value in the DeviceGray color space.

CGContextSetGrayStrokeColor

Sets the current stroke color to a value in the DeviceGray color space.

CGContextSetRGBFillColor

Sets the current fill color to a value in the DeviceRGB color space.

CGContextSetRGBStrokeColor

Sets the current stroke color to a value in the DeviceRGB color space.

CGContextSetShadow

Enables shadowing in a graphics context.

CGContextSetShadowWithColor

Enables shadowing with color a graphics context.

CGContextSetStrokeColor

Sets the current stroke color.

CGContextSetStrokeColorSpace

Sets the stroke color space in a graphics context.

CGContextSetStrokeColorWithColor

Sets the current stroke color in a context, using a CGColor.