Function

vImageHistogramSpecification_ARGB8888(_:_:_:_:)

Performs a histogram specification operation on an ARGB8888 source image.

Declaration

func vImageHistogramSpecification_ARGB8888(_ src: UnsafePointer<vImage_Buffer>, _ dest: UnsafePointer<vImage_Buffer>, _ desired_histogram: UnsafeMutablePointer<UnsafePointer<vImagePixelCount>?>, _ flags: vImage_Flags) -> vImage_Error

Parameters

src

A pointer to a vImage buffer structure that contains the source image.

dest

A pointer to a vImage buffer data structure. You are 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 pointed to by this structure contains the destination image data. When you no longer need the data buffer, you must deallocate the memory.

desiredHistogram

A pointer to an array of four histograms, one each for alpha, red, green, and blue (in that order). These are the desired histograms for the transformed image. Each histogram should be an array with 256 elements.

flags

The options to use. Set the kvImageDoNotTile flag if you plan to perform your own tiling or use multithreading.

Set the kvImageLeaveAlphaUnchanged flag to copy the alpha channel to the destination image unchanged.

Return Value

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

Discussion

The specification operation alters the image histogram so that it more closely resembles a given histogram. The histogram specification operation is done separately for each of the four channels—alpha, red, green, and blue. However, the size and range values are the same for each of the four histograms, and for each of the four desired histograms.

The source and destination buffers must have the same height and the same width.