```
package Image::Leptonica::Func::pix4;
$Image::Leptonica::Func::pix4::VERSION = '0.04';
1;
__END__
=pod
=encoding UTF-8
=head1 NAME
Image::Leptonica::Func::pix4
=head1 VERSION
version 0.04
=head1 C<pix4.c>
pix4.c
This file has these operations:
(1) Pixel histograms
(2) Pixel row/column statistics
(3) Foreground/background estimation
Pixel histogram, rank val, averaging and min/max
NUMA *pixGetGrayHistogram()
NUMA *pixGetGrayHistogramMasked()
NUMA *pixGetGrayHistogramInRect()
l_int32 pixGetColorHistogram()
l_int32 pixGetColorHistogramMasked()
NUMA *pixGetCmapHistogram()
NUMA *pixGetCmapHistogramMasked()
NUMA *pixGetCmapHistogramInRect()
l_int32 pixGetRankValue()
l_int32 pixGetRankValueMaskedRGB()
l_int32 pixGetRankValueMasked()
l_int32 pixGetAverageValue()
l_int32 pixGetAverageMaskedRGB()
l_int32 pixGetAverageMasked()
l_int32 pixGetAverageTiledRGB()
PIX *pixGetAverageTiled()
NUMA *pixRowStats()
NUMA *pixColumnStats()
l_int32 pixGetComponentRange()
l_int32 pixGetExtremeValue()
l_int32 pixGetMaxValueInRect()
l_int32 pixGetBinnedComponentRange()
l_int32 pixGetRankColorArray()
l_int32 pixGetBinnedColor()
PIX *pixDisplayColorArray()
Pixelwise aligned statistics
PIX *pixaGetAlignedStats()
l_int32 pixaExtractColumnFromEachPix()
l_int32 pixGetRowStats()
l_int32 pixGetColumnStats()
l_int32 pixSetPixelColumn()
Foreground/background estimation
l_int32 pixThresholdForFgBg()
l_int32 pixSplitDistributionFgBg()
=head1 FUNCTIONS
=head2 pixColumnStats
l_int32 pixColumnStats ( PIX *pixs, BOX *box, NUMA **pnamean, NUMA **pnamedian, NUMA **pnamode, NUMA **pnamodecount, NUMA **pnavar, NUMA **pnarootvar )
pixColumnStats()
Input: pixs (8 bpp; not cmapped)
box (<optional> clipping box; can be null)
&namean (<optional return> numa of mean values)
&namedian (<optional return> numa of median values)
&namode (<optional return> numa of mode intensity values)
&namodecount (<optional return> numa of mode counts)
&navar (<optional return> numa of variance)
&narootvar (<optional return> numa of square root of variance)
Return: na (numa of requested statistic for each column),
or null on error
Notes:
(1) This computes numas that represent row vectors of statistics,
with each of its values derived from the corresponding col of a Pix.
(2) Use NULL on input to prevent computation of any of the 5 numas.
(3) Other functions that compute pixel column statistics are:
pixCountPixelsByColumn()
pixAverageByColumn()
pixVarianceByColumn()
pixGetColumnStats()
=head2 pixDisplayColorArray
PIX * pixDisplayColorArray ( l_uint32 *carray, l_int32 ncolors, l_int32 side, l_int32 ncols, l_int32 textflag )
pixDisplayColorArray()
Input: carray (array of colors: 0xrrggbb00)
ncolors (size of array)
side (size of each color square; suggest 200)
ncols (number of columns in output color matrix)
textflag (1 to label each square with text; 0 otherwise)
Return: pixd (color array), or null on error
=head2 pixGetAverageMasked
l_int32 pixGetAverageMasked ( PIX *pixs, PIX *pixm, l_int32 x, l_int32 y, l_int32 factor, l_int32 type, l_float32 *pval )
pixGetAverageMasked()
Input: pixs (8 or 16 bpp, or colormapped)
pixm (<optional> 1 bpp mask over which average is to be taken;
use all pixels if null)
x, y (UL corner of pixm relative to the UL corner of pixs;
can be < 0)
factor (subsampling factor; >= 1)
type (L_MEAN_ABSVAL, L_ROOT_MEAN_SQUARE,
L_STANDARD_DEVIATION, L_VARIANCE)
&val (<return> measured value of given 'type')
Return: 0 if OK, 1 on error
Notes:
(1) Use L_MEAN_ABSVAL to get the average value of pixels in pixs
that are under the fg of the optional mask. If the mask
is null, it finds the average of the pixels in pixs.
(2) Likewise, use L_ROOT_MEAN_SQUARE to get the rms value of
pixels in pixs, either masked or not; L_STANDARD_DEVIATION
to get the standard deviation from the mean of the pixels;
L_VARIANCE to get the average squared difference from the
expected value. The variance is the square of the stdev.
For the standard deviation, we use
sqrt(<(<x> - x)>^2) = sqrt(<x^2> - <x>^2)
(3) Set the subsampling @factor > 1 to reduce the amount of
computation.
(4) Clipping of pixm (if it exists) to pixs is done in the inner loop.
(5) Input x,y are ignored unless pixm exists.
=head2 pixGetAverageMaskedRGB
l_int32 pixGetAverageMaskedRGB ( PIX *pixs, PIX *pixm, l_int32 x, l_int32 y, l_int32 factor, l_int32 type, l_float32 *prval, l_float32 *pgval, l_float32 *pbval )
pixGetAverageMaskedRGB()
Input: pixs (32 bpp, or colormapped)
pixm (<optional> 1 bpp mask over which average is to be taken;
use all pixels if null)
x, y (UL corner of pixm relative to the UL corner of pixs;
can be < 0)
factor (subsampling factor; >= 1)
type (L_MEAN_ABSVAL, L_ROOT_MEAN_SQUARE,
L_STANDARD_DEVIATION, L_VARIANCE)
&rval (<return optional> measured red value of given 'type')
&gval (<return optional> measured green value of given 'type')
&bval (<return optional> measured blue value of given 'type')
Return: 0 if OK, 1 on error
Notes:
(1) For usage, see pixGetAverageMasked().
(2) If there is a colormap, it is removed before the 8 bpp
component images are extracted.
=head2 pixGetAverageTiled
PIX * pixGetAverageTiled ( PIX *pixs, l_int32 sx, l_int32 sy, l_int32 type )
pixGetAverageTiled()
Input: pixs (8 bpp, or colormapped)
sx, sy (tile size; must be at least 2 x 2)
type (L_MEAN_ABSVAL, L_ROOT_MEAN_SQUARE, L_STANDARD_DEVIATION)
Return: pixd (average values in each tile), or null on error
Notes:
(1) Only computes for tiles that are entirely contained in pixs.
(2) Use L_MEAN_ABSVAL to get the average abs value within the tile;
L_ROOT_MEAN_SQUARE to get the rms value within each tile;
L_STANDARD_DEVIATION to get the standard dev. from the average
within each tile.
(3) If colormapped, converts to 8 bpp gray.
=head2 pixGetAverageTiledRGB
l_int32 pixGetAverageTiledRGB ( PIX *pixs, l_int32 sx, l_int32 sy, l_int32 type, PIX **ppixr, PIX **ppixg, PIX **ppixb )
pixGetAverageTiledRGB()
Input: pixs (32 bpp, or colormapped)
sx, sy (tile size; must be at least 2 x 2)
type (L_MEAN_ABSVAL, L_ROOT_MEAN_SQUARE, L_STANDARD_DEVIATION)
&pixr (<optional return> tiled 'average' of red component)
&pixg (<optional return> tiled 'average' of green component)
&pixb (<optional return> tiled 'average' of blue component)
Return: 0 if OK, 1 on error
Notes:
(1) For usage, see pixGetAverageTiled().
(2) If there is a colormap, it is removed before the 8 bpp
component images are extracted.
=head2 pixGetAverageValue
l_int32 pixGetAverageValue ( PIX *pixs, l_int32 factor, l_int32 type, l_uint32 *pvalue )
pixGetAverageValue()
Input: pixs (8 bpp, 32 bpp or colormapped)
factor (subsampling factor; integer >= 1)
type (L_MEAN_ABSVAL, L_ROOT_MEAN_SQUARE,
L_STANDARD_DEVIATION, L_VARIANCE)
&value (<return> pixel value corresponding to input rank)
Return: 0 if OK, 1 on error
Notes:
(1) Simple function to get average statistical values of an image.
=head2 pixGetBinnedColor
l_int32 pixGetBinnedColor ( PIX *pixs, PIX *pixg, l_int32 factor, l_int32 nbins, NUMA *nalut, l_uint32 **pcarray, l_int32 debugflag )
pixGetBinnedColor()
Input: pixs (32 bpp)
pixg (8 bpp grayscale version of pixs)
factor (sampling factor along pixel counting direction)
nbins (number of intensity bins)
nalut (LUT for mapping from intensity to bin number)
&carray (<return> array of average color values in each bin)
debugflag (1 to display output debug plots of color
components; 2 to write them as png to file)
Return: 0 if OK; 1 on error
Notes:
(1) This takes a color image, a grayscale (intensity) version,
a LUT from intensity to bin number, and the number of bins.
It computes the average color for pixels whose intensity
is in each bin. This is returned as an array of l_uint32
colors in our standard RGBA ordering.
(2) This function generates equal width intensity bins and
finds the average color in each bin. Compare this with
pixGetRankColorArray(), which rank orders the pixels
by the value of the selected component in each pixel,
sets up bins with equal population (not intensity width!),
and gets the average color in each bin.
=head2 pixGetBinnedComponentRange
l_int32 pixGetBinnedComponentRange ( PIX *pixs, l_int32 nbins, l_int32 factor, l_int32 color, l_int32 *pminval, l_int32 *pmaxval, l_uint32 **pcarray, l_int32 debugflag )
pixGetBinnedComponentRange()
Input: pixs (32 bpp rgb)
nbins (number of equal population bins; must be > 1)
factor (subsampling factor; >= 1)
color (L_SELECT_RED, L_SELECT_GREEN or L_SELECT_BLUE)
&minval (<optional return> minimum value of component)
&maxval (<optional return> maximum value of component)
&carray (<optional return> color array of bins)
debugflag (1 for debug output)
Return: 0 if OK, 1 on error
Notes:
(1) This returns the min and max average values of the
selected color component in the set of rank bins,
where the ranking is done using the specified component.
=head2 pixGetCmapHistogram
NUMA * pixGetCmapHistogram ( PIX *pixs, l_int32 factor )
pixGetCmapHistogram()
Input: pixs (colormapped: d = 2, 4 or 8)
factor (subsampling factor; integer >= 1)
Return: na (histogram of cmap indices), or null on error
Notes:
(1) This generates a histogram of colormap pixel indices,
and is of size 2^d.
(2) Set the subsampling @factor > 1 to reduce the amount of computation.
=head2 pixGetCmapHistogramInRect
NUMA * pixGetCmapHistogramInRect ( PIX *pixs, BOX *box, l_int32 factor )
pixGetCmapHistogramInRect()
Input: pixs (colormapped: d = 2, 4 or 8)
box (<optional>) over which histogram is to be computed;
use full image if null)
factor (subsampling factor; integer >= 1)
Return: na (histogram), or null on error
Notes:
(1) This generates a histogram of colormap pixel indices,
and is of size 2^d.
(2) Set the subsampling @factor > 1 to reduce the amount of computation.
(3) Clipping to the box is done in the inner loop.
=head2 pixGetCmapHistogramMasked
NUMA * pixGetCmapHistogramMasked ( PIX *pixs, PIX *pixm, l_int32 x, l_int32 y, l_int32 factor )
pixGetCmapHistogramMasked()
Input: pixs (colormapped: d = 2, 4 or 8)
pixm (<optional> 1 bpp mask over which histogram is
to be computed; use all pixels if null)
x, y (UL corner of pixm relative to the UL corner of pixs;
can be < 0; these values are ignored if pixm is null)
factor (subsampling factor; integer >= 1)
Return: na (histogram), or null on error
Notes:
(1) This generates a histogram of colormap pixel indices,
and is of size 2^d.
(2) Set the subsampling @factor > 1 to reduce the amount of computation.
(3) Clipping of pixm to pixs is done in the inner loop.
=head2 pixGetColorHistogram
l_int32 pixGetColorHistogram ( PIX *pixs, l_int32 factor, NUMA **pnar, NUMA **pnag, NUMA **pnab )
pixGetColorHistogram()
Input: pixs (rgb or colormapped)
factor (subsampling factor; integer >= 1)
&nar (<return> red histogram)
&nag (<return> green histogram)
&nab (<return> blue histogram)
Return: 0 if OK, 1 on error
Notes:
(1) This generates a set of three 256 entry histograms,
one for each color component (r,g,b).
(2) Set the subsampling @factor > 1 to reduce the amount of computation.
=head2 pixGetColorHistogramMasked
l_int32 pixGetColorHistogramMasked ( PIX *pixs, PIX *pixm, l_int32 x, l_int32 y, l_int32 factor, NUMA **pnar, NUMA **pnag, NUMA **pnab )
pixGetColorHistogramMasked()
Input: pixs (32 bpp rgb, or colormapped)
pixm (<optional> 1 bpp mask over which histogram is
to be computed; use all pixels if null)
x, y (UL corner of pixm relative to the UL corner of pixs;
can be < 0; these values are ignored if pixm is null)
factor (subsampling factor; integer >= 1)
&nar (<return> red histogram)
&nag (<return> green histogram)
&nab (<return> blue histogram)
Return: 0 if OK, 1 on error
Notes:
(1) This generates a set of three 256 entry histograms,
(2) Set the subsampling @factor > 1 to reduce the amount of computation.
(3) Clipping of pixm (if it exists) to pixs is done in the inner loop.
(4) Input x,y are ignored unless pixm exists.
=head2 pixGetColumnStats
l_int32 pixGetColumnStats ( PIX *pixs, l_int32 type, l_int32 nbins, l_int32 thresh, l_float32 *rowvect )
pixGetColumnStats()
Input: pixs (8 bpp; not cmapped)
type (L_MEAN_ABSVAL, L_MEDIAN_VAL, L_MODE_VAL, L_MODE_COUNT)
nbins (of histogram for median and mode; ignored for mean)
thresh (on histogram for mode val; ignored for all other types)
rowvect (vector of results gathered down the columns of pixs)
Return: 0 if OK, 1 on error
Notes:
(1) This computes a row vector of statistics using each
column of a Pix. The result is put in @rowvect.
(2) The @thresh parameter works with L_MODE_VAL only, and
sets a minimum occupancy of the mode bin.
If the occupancy of the mode bin is less than @thresh, the
mode value is returned as 0. To always return the actual
mode value, set @thresh = 0.
(3) What is the meaning of this @thresh parameter?
For each column, the total count in the histogram is h, the
image height. So @thresh, relative to h, gives a measure
of the ratio of the bin width to the width of the distribution.
The larger @thresh, the narrower the distribution must be
for the mode value to be returned (instead of returning 0).
=head2 pixGetComponentRange
l_int32 pixGetComponentRange ( PIX *pixs, l_int32 factor, l_int32 color, l_int32 *pminval, l_int32 *pmaxval )
pixGetComponentRange()
Input: pixs (8 bpp grayscale, 32 bpp rgb, or colormapped)
factor (subsampling factor; >= 1; ignored if colormapped)
color (L_SELECT_RED, L_SELECT_GREEN or L_SELECT_BLUE)
&minval (<optional return> minimum value of component)
&maxval (<optional return> maximum value of component)
Return: 0 if OK, 1 on error
Notes:
(1) If pixs is 8 bpp grayscale, the color selection type is ignored.
=head2 pixGetExtremeValue
l_int32 pixGetExtremeValue ( PIX *pixs, l_int32 factor, l_int32 type, l_int32 *prval, l_int32 *pgval, l_int32 *pbval, l_int32 *pgrayval )
pixGetExtremeValue()
Input: pixs (8 bpp grayscale, 32 bpp rgb, or colormapped)
factor (subsampling factor; >= 1; ignored if colormapped)
type (L_SELECT_MIN or L_SELECT_MAX)
&rval (<optional return> red component)
&gval (<optional return> green component)
&bval (<optional return> blue component)
&grayval (<optional return> min or max gray value)
Return: 0 if OK, 1 on error
Notes:
(1) If pixs is grayscale, the result is returned in &grayval.
Otherwise, if there is a colormap or d == 32,
each requested color component is returned. At least
one color component (address) must be input.
=head2 pixGetGrayHistogram
NUMA * pixGetGrayHistogram ( PIX *pixs, l_int32 factor )
pixGetGrayHistogram()
Input: pixs (1, 2, 4, 8, 16 bpp; can be colormapped)
factor (subsampling factor; integer >= 1)
Return: na (histogram), or null on error
Notes:
(1) If pixs has a colormap, it is converted to 8 bpp gray.
If you want a histogram of the colormap indices, use
pixGetCmapHistogram().
(2) If pixs does not have a colormap, the output histogram is
of size 2^d, where d is the depth of pixs.
(3) This always returns a 256-value histogram of pixel values.
(4) Set the subsampling factor > 1 to reduce the amount of computation.
=head2 pixGetGrayHistogramInRect
NUMA * pixGetGrayHistogramInRect ( PIX *pixs, BOX *box, l_int32 factor )
pixGetGrayHistogramInRect()
Input: pixs (8 bpp, or colormapped)
box (<optional>) over which histogram is to be computed;
use full image if null)
factor (subsampling factor; integer >= 1)
Return: na (histogram), or null on error
Notes:
(1) If pixs is cmapped, it is converted to 8 bpp gray.
If you want a histogram of the colormap indices, use
pixGetCmapHistogramInRect().
(2) This always returns a 256-value histogram of pixel values.
(3) Set the subsampling @factor > 1 to reduce the amount of computation.
=head2 pixGetGrayHistogramMasked
NUMA * pixGetGrayHistogramMasked ( PIX *pixs, PIX *pixm, l_int32 x, l_int32 y, l_int32 factor )
pixGetGrayHistogramMasked()
Input: pixs (8 bpp, or colormapped)
pixm (<optional> 1 bpp mask over which histogram is
to be computed; use all pixels if null)
x, y (UL corner of pixm relative to the UL corner of pixs;
can be < 0; these values are ignored if pixm is null)
factor (subsampling factor; integer >= 1)
Return: na (histogram), or null on error
Notes:
(1) If pixs is cmapped, it is converted to 8 bpp gray.
If you want a histogram of the colormap indices, use
pixGetCmapHistogramMasked().
(2) This always returns a 256-value histogram of pixel values.
(3) Set the subsampling factor > 1 to reduce the amount of computation.
(4) Clipping of pixm (if it exists) to pixs is done in the inner loop.
(5) Input x,y are ignored unless pixm exists.
=head2 pixGetMaxValueInRect
l_int32 pixGetMaxValueInRect ( PIX *pixs, BOX *box, l_uint32 *pmaxval, l_int32 *pxmax, l_int32 *pymax )
pixGetMaxValueInRect()
Input: pixs (8 bpp or 32 bpp grayscale; no color space components)
box (<optional> region; set box = NULL to use entire pixs)
&maxval (<optional return> max value in region)
&xmax (<optional return> x location of max value)
&ymax (<optional return> y location of max value)
Return: 0 if OK, 1 on error
Notes:
(1) This can be used to find the maximum and its location
in a 2-dimensional histogram, where the x and y directions
represent two color components (e.g., saturation and hue).
(2) Note that here a 32 bpp pixs has pixel values that are simply
numbers. They are not 8 bpp components in a colorspace.
=head2 pixGetRankColorArray
l_int32 pixGetRankColorArray ( PIX *pixs, l_int32 nbins, l_int32 type, l_int32 factor, l_uint32 **pcarray, l_int32 debugflag )
pixGetRankColorArray()
Input: pixs (32 bpp or cmapped)
nbins (number of equal population bins; must be > 1)
type (color selection flag)
factor (subsampling factor; integer >= 1)
&carray (<return> array of colors, ranked by intensity)
debugflag (1 to display color squares and plots of color
components; 2 to write them as png to file)
Return: 0 if OK, 1 on error
Notes:
(1) The color selection flag is one of: L_SELECT_RED, L_SELECT_GREEN,
L_SELECT_BLUE, L_SELECT_MIN, L_SELECT_MAX.
(2) Then it finds the histogram of the selected component in each
RGB pixel. For each of the @nbins sets of pixels,
ordered by this component value, find the average color,
and return this as a "rank color" array. The output array
has @nbins colors.
(3) Set the subsampling factor > 1 to reduce the amount of
computation. Typically you want at least 10,000 pixels
for reasonable statistics.
(4) The rank color as a function of rank can then be found from
rankint = (l_int32)(rank * (nbins - 1) + 0.5);
extractRGBValues(array[rankint], &rval, &gval, &bval);
where the rank is in [0.0 ... 1.0].
This function is meant to be simple and approximate.
(5) Compare this with pixGetBinnedColor(), which generates equal
width intensity bins and finds the average color in each bin.
=head2 pixGetRankValue
l_int32 pixGetRankValue ( PIX *pixs, l_int32 factor, l_float32 rank, l_uint32 *pvalue )
pixGetRankValue()
Input: pixs (8 bpp, 32 bpp or colormapped)
factor (subsampling factor; integer >= 1)
rank (between 0.0 and 1.0; 1.0 is brightest, 0.0 is darkest)
&value (<return> pixel value corresponding to input rank)
Return: 0 if OK, 1 on error
Notes:
(1) Simple function to get rank values of an image.
For a color image, the median value (rank = 0.5) can be
used to linearly remap the colors based on the median
of a target image, using pixLinearMapToTargetColor().
=head2 pixGetRankValueMasked
l_int32 pixGetRankValueMasked ( PIX *pixs, PIX *pixm, l_int32 x, l_int32 y, l_int32 factor, l_float32 rank, l_float32 *pval, NUMA **pna )
pixGetRankValueMasked()
Input: pixs (8 bpp, or colormapped)
pixm (<optional> 1 bpp mask over which rank val is to be taken;
use all pixels if null)
x, y (UL corner of pixm relative to the UL corner of pixs;
can be < 0; these values are ignored if pixm is null)
factor (subsampling factor; integer >= 1)
rank (between 0.0 and 1.0; 1.0 is brightest, 0.0 is darkest)
&val (<return> pixel value corresponding to input rank)
&na (<optional return> of histogram)
Return: 0 if OK, 1 on error
Notes:
(1) Computes the rank value of pixels in pixs that are under
the fg of the optional mask. If the mask is null, it
computes the average of the pixels in pixs.
(2) Set the subsampling @factor > 1 to reduce the amount of
computation.
(3) Clipping of pixm (if it exists) to pixs is done in the inner loop.
(4) Input x,y are ignored unless pixm exists.
(5) The rank must be in [0.0 ... 1.0], where the brightest pixel
has rank 1.0. For the median pixel value, use 0.5.
(6) The histogram can optionally be returned, so that other rank
values can be extracted without recomputing the histogram.
In that case, just use
numaHistogramGetValFromRank(na, rank, &val);
on the returned Numa for additional rank values.
=head2 pixGetRankValueMaskedRGB
l_int32 pixGetRankValueMaskedRGB ( PIX *pixs, PIX *pixm, l_int32 x, l_int32 y, l_int32 factor, l_float32 rank, l_float32 *prval, l_float32 *pgval, l_float32 *pbval )
pixGetRankValueMaskedRGB()
Input: pixs (32 bpp)
pixm (<optional> 1 bpp mask over which rank val is to be taken;
use all pixels if null)
x, y (UL corner of pixm relative to the UL corner of pixs;
can be < 0; these values are ignored if pixm is null)
factor (subsampling factor; integer >= 1)
rank (between 0.0 and 1.0; 1.0 is brightest, 0.0 is darkest)
&rval (<optional return> red component val for to input rank)
&gval (<optional return> green component val for to input rank)
&bval (<optional return> blue component val for to input rank)
Return: 0 if OK, 1 on error
Notes:
(1) Computes the rank component values of pixels in pixs that
are under the fg of the optional mask. If the mask is null, it
computes the average of the pixels in pixs.
(2) Set the subsampling @factor > 1 to reduce the amount of
computation.
(4) Input x,y are ignored unless pixm exists.
(5) The rank must be in [0.0 ... 1.0], where the brightest pixel
has rank 1.0. For the median pixel value, use 0.5.
=head2 pixGetRowStats
l_int32 pixGetRowStats ( PIX *pixs, l_int32 type, l_int32 nbins, l_int32 thresh, l_float32 *colvect )
pixGetRowStats()
Input: pixs (8 bpp; not cmapped)
type (L_MEAN_ABSVAL, L_MEDIAN_VAL, L_MODE_VAL, L_MODE_COUNT)
nbins (of histogram for median and mode; ignored for mean)
thresh (on histogram for mode; ignored for mean and median)
colvect (vector of results gathered across the rows of pixs)
Return: 0 if OK, 1 on error
Notes:
(1) This computes a column vector of statistics using each
row of a Pix. The result is put in @colvect.
(2) The @thresh parameter works with L_MODE_VAL only, and
sets a minimum occupancy of the mode bin.
If the occupancy of the mode bin is less than @thresh, the
mode value is returned as 0. To always return the actual
mode value, set @thresh = 0.
(3) What is the meaning of this @thresh parameter?
For each row, the total count in the histogram is w, the
image width. So @thresh, relative to w, gives a measure
of the ratio of the bin width to the width of the distribution.
The larger @thresh, the narrower the distribution must be
for the mode value to be returned (instead of returning 0).
(4) If the Pix consists of a set of corresponding columns,
one for each Pix in a Pixa, the width of the Pix is the
number of Pix in the Pixa and the column vector can
be stored as a column in a Pix of the same size as
each Pix in the Pixa.
=head2 pixRowStats
l_int32 pixRowStats ( PIX *pixs, BOX *box, NUMA **pnamean, NUMA **pnamedian, NUMA **pnamode, NUMA **pnamodecount, NUMA **pnavar, NUMA **pnarootvar )
pixRowStats()
Input: pixs (8 bpp; not cmapped)
box (<optional> clipping box; can be null)
&namean (<optional return> numa of mean values)
&namedian (<optional return> numa of median values)
&namode (<optional return> numa of mode intensity values)
&namodecount (<optional return> numa of mode counts)
&navar (<optional return> numa of variance)
&narootvar (<optional return> numa of square root of variance)
Return: na (numa of requested statistic for each row), or null on error
Notes:
(1) This computes numas that represent column vectors of statistics,
with each of its values derived from the corresponding row of a Pix.
(2) Use NULL on input to prevent computation of any of the 5 numas.
(3) Other functions that compute pixel row statistics are:
pixCountPixelsByRow()
pixAverageByRow()
pixVarianceByRow()
pixGetRowStats()
=head2 pixSetPixelColumn
l_int32 pixSetPixelColumn ( PIX *pix, l_int32 col, l_float32 *colvect )
pixSetPixelColumn()
Input: pix (8 bpp; not cmapped)
col (column index)
colvect (vector of floats)
Return: 0 if OK, 1 on error
=head2 pixSplitDistributionFgBg
l_int32 pixSplitDistributionFgBg ( PIX *pixs, l_float32 scorefract, l_int32 factor, l_int32 *pthresh, l_int32 *pfgval, l_int32 *pbgval, l_int32 debugflag )
pixSplitDistributionFgBg()
Input: pixs (any depth; cmapped ok)
scorefract (fraction of the max score, used to determine
the range over which the histogram min is searched)
factor (subsampling factor; integer >= 1)
&thresh (<optional return> best threshold for separating)
&fgval (<optional return> average foreground value)
&bgval (<optional return> average background value)
debugflag (1 for plotting of distribution and split point)
Return: 0 if OK, 1 on error
Notes:
(1) See numaSplitDistribution() for details on the underlying
method of choosing a threshold.
=head2 pixThresholdForFgBg
l_int32 pixThresholdForFgBg ( PIX *pixs, l_int32 factor, l_int32 thresh, l_int32 *pfgval, l_int32 *pbgval )
pixThresholdForFgBg()
Input: pixs (any depth; cmapped ok)
factor (subsampling factor; integer >= 1)
thresh (threshold for generating foreground mask)
&fgval (<optional return> average foreground value)
&bgval (<optional return> average background value)
Return: 0 if OK, 1 on error
=head2 pixaExtractColumnFromEachPix
l_int32 pixaExtractColumnFromEachPix ( PIXA *pixa, l_int32 col, PIX *pixd )
pixaExtractColumnFromEachPix()
Input: pixa (of identically sized, 8 bpp; not cmapped)
col (column index)
pixd (pix into which each column is inserted)
Return: 0 if OK, 1 on error
=head2 pixaGetAlignedStats
PIX * pixaGetAlignedStats ( PIXA *pixa, l_int32 type, l_int32 nbins, l_int32 thresh )
pixaGetAlignedStats()
Input: pixa (of identically sized, 8 bpp pix; not cmapped)
type (L_MEAN_ABSVAL, L_MEDIAN_VAL, L_MODE_VAL, L_MODE_COUNT)
nbins (of histogram for median and mode; ignored for mean)
thresh (on histogram for mode val; ignored for all other types)
Return: pix (with pixelwise aligned stats), or null on error.
Notes:
(1) Each pixel in the returned pix represents an average
(or median, or mode) over the corresponding pixels in each
pix in the pixa.
(2) The @thresh parameter works with L_MODE_VAL only, and
sets a minimum occupancy of the mode bin.
If the occupancy of the mode bin is less than @thresh, the
mode value is returned as 0. To always return the actual
mode value, set @thresh = 0. See pixGetRowStats().
=head1 AUTHOR
Zakariyya Mughal <zmughal@cpan.org>
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2014 by Zakariyya Mughal.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut
```