Function

CGBitmapContextGetAlphaInfo

Returns the alpha information associated with the context, which indicates how a bitmap context handles the alpha component.

Declaration

CGImageAlphaInfo CGBitmapContextGetAlphaInfo(CGContextRef context);

Parameters

context

A bitmap context.

Return Value

A bitmap information constant. If the specified context is not a bitmap context, kCGImageAlphaNone is returned.

Discussion

Every bitmap context contains an attribute that specifies whether the bitmap contains an alpha component, and how it is generated. The alpha component determines the opacity of a pixel when it is drawn.

See Also

Getting Information About Bitmap Contexts

CGBitmapContextGetBitmapInfo

Obtains the bitmap information associated with a bitmap graphics context.

CGBitmapContextGetBitsPerComponent

Returns the bits per component of a bitmap context.

CGBitmapContextGetBitsPerPixel

Returns the bits per pixel of a bitmap context.

CGBitmapContextGetBytesPerRow

Returns the bytes per row of a bitmap context.

CGBitmapContextGetColorSpace

Returns the color space of a bitmap context.

CGBitmapContextGetData

Returns a pointer to the image data associated with a bitmap context.

CGBitmapContextGetHeight

Returns the height in pixels of a bitmap context.

CGBitmapContextGetWidth

Returns the width in pixels of a bitmap context.