vImagePremultiplyData_RGBAFFFF(_:_:_:)

Transforms a floating-point 32-bit-per-channel, 4-channel ARGB buffer from nonpremultiplied alpha format to premultiplied alpha format.

Declaration

func vImagePremultiplyData_RGBAFFFF(_ src: UnsafePointer<vImage_Buffer>, _ dest: UnsafePointer<vImage_Buffer>, _ flags: vImage_Flags) -> vImage_Error

src:
The source vImage buffer.
dest:
A pointer to the destination vImage buffer structure. You’re responsible for filling out the Height, Width, and Rowbytes fields of this structure, and for allocating a data buffer of the appropriate size. On return, the data buffer this structure points to contains the destination image data. When you no longer need the data buffer, deallocate the memory to prevent memory leaks.
flags:
The options to use when performing the operation. If your code implements its own tiling or its own multithreading, pass Kvimagedonottile; otherwise, pass Kvimagenoflags.

kvImageNoError; otherwise, one of the error codes in Data Types and Constants.

This function multiplies color channels by the alpha channel using the following code:

float destColor = src * alpha;
float destAlpha = alpha;