vImageHistogramSpecification_ARGB8888(_:_:_:_:)
Specifies the histogram of an 8-bit-per-channel, 4-channel interleaved buffer.
Declaration
func vImageHistogramSpecification_ARGB8888(_ src: UnsafePointer<vImage_Buffer>, _ dest: UnsafePointer<vImage_Buffer>, _ desired_histogram: UnsafeMutablePointer<UnsafePointer<vImagePixelCount>?>, _ flags: vImage_Flags) -> vImage_ErrorParameters
- 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.
- desired_histogram:
The histograms that the operation applies to the source buffer.
- 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.
To specify that the function doesn’t apply the operation to the alpha channel, set the Kvimageleavealphaunchanged flag.
Return Value
kvImageNoError; otherwise, one of the error codes in Data Types and Constants.
Discussion
Use this function to apply a histogram — that you’ve generated using vImageHistogramSpecification_ARGBFFFF(_:_:_:_:_:_:_:_:) — to each channel of another image.
The following code applies a histogram to a 4-channel interleaved vImage buffer:
// `histogramAlpha`, `histogramRed`, `histogramGreen`, and `histogramBlue` are `entryCount` element arrays.
histogramAlpha.withUnsafeBufferPointer { zeroPtr in
histogramRed.withUnsafeBufferPointer { onePtr in
histogramGreen.withUnsafeBufferPointer { twoPtr in
histogramBlue.withUnsafeBufferPointer { threePtr in
var histogramBins = [zeroPtr.baseAddress, onePtr.baseAddress,
twoPtr.baseAddress, threePtr.baseAddress]
histogramBins.withUnsafeMutableBufferPointer { histogramBinsPtr in
// `buffer` is a `vImage_Buffer` structure
_ = vImageHistogramSpecification_ARGB8888(&buffer, &buffer,
histogramBinsPtr.baseAddress!,
vImage_Flags(kvImageNoFlags))
}
}
}
}
}