MPSImageHistogramInfo(3) MetalPerformanceShaders.framework MPSImageHistogramInfo(3)NAME
MPSImageHistogramInfo - Specifies information to compute the histogram for channels of an image.
SYNOPSIS
#include <MPSImageHistogram.h>
Public Attributes
NSUInteger numberOfHistogramEntries
BOOL histogramForAlpha
vector_float4 minPixelValue
vector_float4 maxPixelValue
Detailed Description
Specifies information to compute the histogram for channels of an image.
MPSImageHistogram.h MetalPerformanceShaders.framework
Copyright:
Copyright (c) 2015 Apple Inc. All rights reserved. MetalPerformanceShaders histogram filters
Member Data Documentation
BOOL MPSImageHistogramInfo::histogramForAlpha
Specifies whether the histogram for the alpha channel should be computed or not.
vector_float4 MPSImageHistogramInfo::maxPixelValue
Specifies the maximum pixel value. Any pixel value greater than this will be clipped to this value (for the purposes of histogram
calculation), and assigned to the last histogram entry. This maximum value is applied to each of the four channels separately.
vector_float4 MPSImageHistogramInfo::minPixelValue
Specifies the minimum pixel value. Any pixel value less than this will be clipped to this value (for the purposes of histogram
calculation), and assigned to the first histogram entry. This minimum value is applied to each of the four channels separately.
NSUInteger MPSImageHistogramInfo::numberOfHistogramEntries
Specifies the number of histogram entries, or 'bins' for each channel. For example, if you want 256 histogram bins then
numberOfHistogramEntries must be set to 256. The value stored in each histogram bin is a 32-bit unsigned integer. The size of the histogram
buffer in which these bins will be stored should be >= numberOfHistogramEntries * sizeof(uint32_t) * number of channels in the image.
numberOfHistogramEntries must be a power of 2 and is a minimum of 256 bins.
Author
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Version MetalPerformanceShaders-100 Thu Feb 8 2018 MPSImageHistogramInfo(3)
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mlib_ImageHistogram2(3MLIB) mediaLib Library Functions mlib_ImageHistogram2(3MLIB)NAME
mlib_ImageHistogram2 - histogram
SYNOPSIS
cc [ flag... ] file... -lmlib [ library... ]
#include <mlib.h>
mlib_status mlib_ImageHistogram2(mlib_s32 **histo, const mlib_image *img, const mlib_s32 *numBins, const mlib_s32 *lowValue, const mlib_s32
*highValue, mlib_s32 xStart, mlib_s32 yStart, mlib_s32 xPeriod, mlib_s32 yPeriod);
DESCRIPTION
The mlib_ImageHistogram2() function creates a histogram by scanning an image, counting the number of pixels within a given range for each
channel of the image, and then generating a histogram.
The image can have 1, 2, 3 or 4 channels. The data type of the image can be MLIB_BYTE, MLIB_SHORT, MLIB_USHORT, or MLIB_INT. The histogram
must have the same number of channels as the image has.
One entry of the histogram, or a bin, is used to accumulate the number of pixels within a certain sub-range. The legal pixel range and the
number of bins may be controlled separately.
If binWidth is defined as (highValue - lowValue )/numBins then bin i counts pixel values in the following range:
lowValue + i*binWidth <= x < lowValue + (i + 1)*binWidth
The set of pixels scanned may furthermore be reduced by specifying xPeriod and yPeriod parameters that specify the sampling rate along each
axis.
The set of pixels to be accumulated may be obtained from the following equation:
x = xStart + p*xPeriod; 0 <= p < (w - xStart)/xPeriod
y = yStart + q*yPeriod; 0 <= q < (h - yStart)/yPeriod
It is the user's responsibility to clear the histogram table before this function is called and to ensure that the histogram table supplied
is suitable for the source image and the parameters. Otherwise, the result of this function is undefined.
The range from lowValue[k] to (highValue[k] - 1) must be a valid subrange of the image type range.
PARAMETERS
The function takes the following arguments:
histo Pointer to histogram. The format of the histogram is histo[channel][index]. The index values for channel i can be 0, 1,
..., numBins[i]-1.
img Pointer to source image.
numBins The number of bins for each channel of the image.
lowValue The lowest pixel value checked for each channel.
highValue The highest pixel value checked for each channel. When counting the pixel values, highValue is not included.
xStart The initial X sample coordinate.
yStart The initial Y sample coordinate.
xPeriod The X sampling rate. xPeriod >= 1.
yPeriod The Y sampling rate. yPeriod >= 1.
RETURN VALUES
The function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Evolving |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO mlib_ImageHistogram(3MLIB), attributes(5)SunOS 5.10 10 Nov 2004 mlib_ImageHistogram2(3MLIB)