Contents

vImagePremultiplyData_RGBA16Q12(_:_:_:)

Transforms a fixed-point 16-bit-per-channel, 4-channel RGBA buffer from nonpremultiplied alpha format to premultiplied alpha format.

Declaration

func vImagePremultiplyData_RGBA16Q12(_ src: UnsafePointer<vImage_Buffer>, _ dest: UnsafePointer<vImage_Buffer>, _ flags: vImage_Flags) -> vImage_Error

Parameters

  • 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.

Return Value

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

Discussion

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

int16_t destColor = CLAMP((src * alpha + 2048) / 4096, INT16_MIN, INT16_MAX);
int16_t destAlpha = alpha;

See Also

Related Documentation

Converting from unpremultiplied to premultiplied format