NAME
Image::Leptonica::Func::pix3
VERSION
version 0.04
pix3.c
pix3.c
This file has these operations:
(1) Mask-directed operations
(2) Full-image bit-logical operations
(3) Foreground pixel counting operations on 1 bpp images
(4) Average and variance of pixel values
(5) Mirrored tiling of a smaller image
Masked operations
l_int32 pixSetMasked()
l_int32 pixSetMaskedGeneral()
l_int32 pixCombineMasked()
l_int32 pixCombineMaskedGeneral()
l_int32 pixPaintThroughMask()
PIX *pixPaintSelfThroughMask()
PIX *pixMakeMaskFromLUT()
PIX *pixSetUnderTransparency()
One and two-image boolean operations on arbitrary depth images
PIX *pixInvert()
PIX *pixOr()
PIX *pixAnd()
PIX *pixXor()
PIX *pixSubtract()
Foreground pixel counting in 1 bpp images
l_int32 pixZero()
l_int32 pixForegroundFraction()
NUMA *pixaCountPixels()
l_int32 pixCountPixels()
NUMA *pixCountByRow()
NUMA *pixCountByColumn()
NUMA *pixCountPixelsByRow()
NUMA *pixCountPixelsByColumn()
l_int32 pixCountPixelsInRow()
NUMA *pixGetMomentByColumn()
l_int32 pixThresholdPixelSum()
l_int32 *makePixelSumTab8()
l_int32 *makePixelCentroidTab8()
Average of pixel values in gray images
NUMA *pixAverageByRow()
NUMA *pixAverageByColumn()
l_int32 pixAverageInRect()
Variance of pixel values in gray images
NUMA *pixVarianceByRow()
NUMA *pixVarianceByColumn()
l_int32 pixVarianceInRect()
Average of absolute value of pixel differences in gray images
NUMA *pixAbsDiffByRow()
NUMA *pixAbsDiffByColumn()
l_int32 pixAbsDiffInRect()
l_int32 pixAbsDiffOnLine()
Count of pixels with specific value *
l_int32 pixCountArbInRect()
Mirrored tiling
PIX *pixMirroredTiling()
Static helper function
static l_int32 findTilePatchCenter()FUNCTIONS
makePixelCentroidTab8
l_int32 * makePixelCentroidTab8 ( void )
makePixelCentroidTab8()
Input: void
Return: table of 256 l_int32, or null on error
Notes:
(1) This table of integers gives the centroid weight of the 1 bits
in the 8 bit index. In other words, if sumtab is obtained by
makePixelSumTab8, and centroidtab is obtained by
makePixelCentroidTab8, then, for 1 <= i <= 255,
centroidtab[i] / (float)sumtab[i]
is the centroid of the 1 bits in the 8-bit index i, where the
MSB is considered to have position 0 and the LSB is considered
to have position 7.makePixelSumTab8
l_int32 * makePixelSumTab8 ( void )
makePixelSumTab8()
Input: void
Return: table of 256 l_int32, or null on error
Notes:
(1) This table of integers gives the number of 1 bits
in the 8 bit index.pixAbsDiffByColumn
NUMA * pixAbsDiffByColumn ( PIX *pix, BOX *box )
pixAbsDiffByColumn()
Input: pix (8 bpp; no colormap)
box (<optional> clipping box for region; can be null)
Return: na of abs val pixel difference averages by column,
or null on error
Notes:
(1) This is an average over differences of adjacent pixels along
each column.
(2) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.pixAbsDiffByRow
NUMA * pixAbsDiffByRow ( PIX *pix, BOX *box )
pixAbsDiffByRow()
Input: pix (8 bpp; no colormap)
box (<optional> clipping box for region; can be null)
Return: na of abs val pixel difference averages by row, or null on error
Notes:
(1) This is an average over differences of adjacent pixels along
each row.
(2) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.pixAbsDiffInRect
l_int32 pixAbsDiffInRect ( PIX *pix, BOX *box, l_int32 dir, l_float32 *pabsdiff )
pixAbsDiffInRect()
Input: pix (8 bpp; not cmapped)
box (<optional> if null, use entire image)
dir (differences along L_HORIZONTAL_LINE or L_VERTICAL_LINE)
&absdiff (<return> average of abs diff pixel values in region)
Return: 0 if OK; 1 on error
Notes:
(1) This gives the average over the abs val of differences of
adjacent pixels values, along either each
row: dir == L_HORIZONTAL_LINE
column: dir == L_VERTICAL_LINEpixAbsDiffOnLine
l_int32 pixAbsDiffOnLine ( PIX *pix, l_int32 x1, l_int32 y1, l_int32 x2, l_int32 y2, l_float32 *pabsdiff )
pixAbsDiffOnLine()
Input: pix (8 bpp; not cmapped)
x1, y1 (first point; x1 <= x2, y1 <= y2)
x2, y2 (first point)
&absdiff (<return> average of abs diff pixel values on line)
Return: 0 if OK; 1 on error
Notes:
(1) This gives the average over the abs val of differences of
adjacent pixels values, along a line that is either horizontal
or vertical.
(2) If horizontal, require x1 < x2; if vertical, require y1 < y2.pixAnd
PIX * pixAnd ( PIX *pixd, PIX *pixs1, PIX *pixs2 )
pixAnd()
Input: pixd (<optional>; this can be null, equal to pixs1,
different from pixs1)
pixs1 (can be == pixd)
pixs2 (must be != pixd)
Return: pixd always
Notes:
(1) This gives the intersection of two images with equal depth,
aligning them to the the UL corner. pixs1 and pixs2
need not have the same width and height.
(2) There are 3 cases:
(a) pixd == null, (src1 & src2) --> new pixd
(b) pixd == pixs1, (src1 & src2) --> src1 (in-place)
(c) pixd != pixs1, (src1 & src2) --> input pixd
(3) For clarity, if the case is known, use these patterns:
(a) pixd = pixAnd(NULL, pixs1, pixs2);
(b) pixAnd(pixs1, pixs1, pixs2);
(c) pixAnd(pixd, pixs1, pixs2);
(4) The size of the result is determined by pixs1.
(5) The depths of pixs1 and pixs2 must be equal.
(6) Note carefully that the order of pixs1 and pixs2 only matters
for the in-place case. For in-place, you must have
pixd == pixs1. Setting pixd == pixs2 gives an incorrect
result: the copy puts pixs1 image data in pixs2, and
the rasterop is then between pixs2 and pixs2 (a no-op).pixAverageByColumn
NUMA * pixAverageByColumn ( PIX *pix, BOX *box, l_int32 type )
pixAverageByColumn()
Input: pix (8 or 16 bpp; no colormap)
box (<optional> clipping box for sum; can be null)
type (L_WHITE_IS_MAX, L_BLACK_IS_MAX)
Return: na of pixel averages by column, or null on error
Notes:
(1) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.
(2) If type == L_BLACK_IS_MAX, black pixels get the maximum
value (0xff for 8 bpp, 0xffff for 16 bpp) and white get 0.pixAverageByRow
NUMA * pixAverageByRow ( PIX *pix, BOX *box, l_int32 type )
pixAverageByRow()
Input: pix (8 or 16 bpp; no colormap)
box (<optional> clipping box for sum; can be null)
type (L_WHITE_IS_MAX, L_BLACK_IS_MAX)
Return: na of pixel averages by row, or null on error
Notes:
(1) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.
(2) If type == L_BLACK_IS_MAX, black pixels get the maximum
value (0xff for 8 bpp, 0xffff for 16 bpp) and white get 0.pixAverageInRect
l_int32 pixAverageInRect ( PIX *pix, BOX *box, l_float32 *pave )
pixAverageInRect()
Input: pix (1, 2, 4, 8 bpp; not cmapped)
box (<optional> if null, use entire image)
&ave (<return> average of pixel values in region)
Return: 0 if OK; 1 on errorpixCombineMasked
l_int32 pixCombineMasked ( PIX *pixd, PIX *pixs, PIX *pixm )
pixCombineMasked()
Input: pixd (1 bpp, 8 bpp gray or 32 bpp rgb; no cmap)
pixs (1 bpp, 8 bpp gray or 32 bpp rgb; no cmap)
pixm (<optional> 1 bpp mask; no operation if NULL)
Return: 0 if OK; 1 on error
Notes:
(1) In-place operation; pixd is changed.
(2) This sets each pixel in pixd that co-locates with an ON
pixel in pixm to the corresponding value of pixs.
(3) pixs and pixd must be the same depth and not colormapped.
(4) All three input pix are aligned at the UL corner, and the
operation is clipped to the intersection of all three images.
(5) If pixm == NULL, it's a no-op.
(6) Implementation: see notes in pixCombineMaskedGeneral().
For 8 bpp selective masking, you might guess that it
would be faster to generate an 8 bpp version of pixm,
using pixConvert1To8(pixm, 0, 255), and then use a
general combine operation
d = (d & ~m) | (s & m)
on a word-by-word basis. Not always. The word-by-word
combine takes a time that is independent of the mask data.
If the mask is relatively sparse, the byte-check method
is actually faster!pixCombineMaskedGeneral
l_int32 pixCombineMaskedGeneral ( PIX *pixd, PIX *pixs, PIX *pixm, l_int32 x, l_int32 y )
pixCombineMaskedGeneral()
Input: pixd (1 bpp, 8 bpp gray or 32 bpp rgb)
pixs (1 bpp, 8 bpp gray or 32 bpp rgb)
pixm (<optional> 1 bpp mask)
x, y (origin of pixs and pixm relative to pixd; can be negative)
Return: 0 if OK; 1 on error
Notes:
(1) In-place operation; pixd is changed.
(2) This is a generalized version of pixCombinedMasked(), where
the source and mask can be placed at the same (arbitrary)
location relative to pixd.
(3) pixs and pixd must be the same depth and not colormapped.
(4) The UL corners of both pixs and pixm are aligned with
the point (x, y) of pixd, and the operation is clipped to
the intersection of all three images.
(5) If pixm == NULL, it's a no-op.
(6) Implementation. There are two ways to do these. In the first,
we use rasterop, ORing the part of pixs under the mask
with pixd (which has been appropriately cleared there first).
In the second, the mask is used one pixel at a time to
selectively replace pixels of pixd with those of pixs.
Here, we use rasterop for 1 bpp and pixel-wise replacement
for 8 and 32 bpp. To use rasterop for 8 bpp, for example,
we must first generate an 8 bpp version of the mask.
The code is simple:
Pix *pixm8 = pixConvert1To8(NULL, pixm, 0, 255);
Pix *pixt = pixAnd(NULL, pixs, pixm8);
pixRasterop(pixd, x, y, wmin, hmin, PIX_DST & PIX_NOT(PIX_SRC),
pixm8, 0, 0);
pixRasterop(pixd, x, y, wmin, hmin, PIX_SRC | PIX_DST,
pixt, 0, 0);
pixDestroy(&pixt);
pixDestroy(&pixm8);pixCountArbInRect
l_int32 pixCountArbInRect ( PIX *pixs, BOX *box, l_int32 val, l_int32 factor, l_int32 *pcount )
pixCountArbInRect()
Input: pixs (8 bpp, or colormapped)
box (<optional>) over which count is made;
use entire image null)
val (pixel value to count)
factor (subsampling factor; integer >= 1)
&count (<return> count; estimate it if factor > 1)
Return: na (histogram), or null on error
Notes:
(1) If pixs is cmapped, @val is compared to the colormap index;
otherwise, @val is compared to the grayscale value.
(2) Set the subsampling @factor > 1 to reduce the amount of computation.
If @factor > 1, multiply the count by @factor * @factor.pixCountByColumn
NUMA * pixCountByColumn ( PIX *pix, BOX *box )
pixCountByColumn()
Input: pix (1 bpp)
box (<optional> clipping box for count; can be null)
Return: na of number of ON pixels by column, or null on error
Notes:
(1) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.pixCountByRow
NUMA * pixCountByRow ( PIX *pix, BOX *box )
pixCountByRow()
Input: pix (1 bpp)
box (<optional> clipping box for count; can be null)
Return: na of number of ON pixels by row, or null on error
Notes:
(1) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.pixCountPixels
l_int32 pixCountPixels ( PIX *pix, l_int32 *pcount, l_int32 *tab8 )
pixCountPixels()
Input: pix (1 bpp)
&count (<return> count of ON pixels)
tab8 (<optional> 8-bit pixel lookup table)
Return: 0 if OK; 1 on errorpixCountPixelsByColumn
NUMA * pixCountPixelsByColumn ( PIX *pix )
pixCountPixelsByColumn()
Input: pix (1 bpp)
Return: na of counts in each column, or null on errorpixCountPixelsByRow
NUMA * pixCountPixelsByRow ( PIX *pix, l_int32 *tab8 )
pixCountPixelsByRow()
Input: pix (1 bpp)
tab8 (<optional> 8-bit pixel lookup table)
Return: na of counts, or null on errorpixCountPixelsInRow
l_int32 pixCountPixelsInRow ( PIX *pix, l_int32 row, l_int32 *pcount, l_int32 *tab8 )
pixCountPixelsInRow()
Input: pix (1 bpp)
row number
&count (<return> sum of ON pixels in raster line)
tab8 (<optional> 8-bit pixel lookup table)
Return: 0 if OK; 1 on errorpixForegroundFraction
l_int32 pixForegroundFraction ( PIX *pix, l_float32 *pfract )
pixForegroundFraction()
Input: pix (1 bpp)
&fract (<return> fraction of ON pixels)
Return: 0 if OK; 1 on errorpixGetMomentByColumn
NUMA * pixGetMomentByColumn ( PIX *pix, l_int32 order )
pixGetMomentByColumn()
Input: pix (1 bpp)
order (of moment, either 1 or 2)
Return: na of first moment of fg pixels, by column, or null on errorpixInvert
PIX * pixInvert ( PIX *pixd, PIX *pixs )
pixInvert()
Input: pixd (<optional>; this can be null, equal to pixs,
or different from pixs)
pixs
Return: pixd, or null on error
Notes:
(1) This inverts pixs, for all pixel depths.
(2) There are 3 cases:
(a) pixd == null, ~src --> new pixd
(b) pixd == pixs, ~src --> src (in-place)
(c) pixd != pixs, ~src --> input pixd
(3) For clarity, if the case is known, use these patterns:
(a) pixd = pixInvert(NULL, pixs);
(b) pixInvert(pixs, pixs);
(c) pixInvert(pixd, pixs);pixMakeMaskFromLUT
PIX * pixMakeMaskFromLUT ( PIX *pixs, l_int32 *tab )
pixMakeMaskFromLUT()
Input: pixs (2, 4 or 8 bpp; can be colormapped)
tab (256-entry LUT; 1 means to write to mask)
Return: pixd (1 bpp mask), or null on error
Notes:
(1) This generates a 1 bpp mask image, where a 1 is written in
the mask for each pixel in pixs that has a value corresponding
to a 1 in the LUT.
(2) The LUT should be of size 256.pixMirroredTiling
PIX * pixMirroredTiling ( PIX *pixs, l_int32 w, l_int32 h )
pixMirroredTiling()
Input: pixs (8 or 32 bpp, small tile; to be replicated)
w, h (dimensions of output pix)
Return: pixd (usually larger pix, mirror-tiled with pixs),
or null on error
Notes:
(1) This uses mirrored tiling, where each row alternates
with LR flips and every column alternates with TB
flips, such that the result is a tiling with identical
2 x 2 tiles, each of which is composed of these transforms:
-----------------
| 1 | LR |
-----------------
| TB | LR/TB |
-----------------pixOr
PIX * pixOr ( PIX *pixd, PIX *pixs1, PIX *pixs2 )
pixOr()
Input: pixd (<optional>; this can be null, equal to pixs1,
different from pixs1)
pixs1 (can be == pixd)
pixs2 (must be != pixd)
Return: pixd always
Notes:
(1) This gives the union of two images with equal depth,
aligning them to the the UL corner. pixs1 and pixs2
need not have the same width and height.
(2) There are 3 cases:
(a) pixd == null, (src1 | src2) --> new pixd
(b) pixd == pixs1, (src1 | src2) --> src1 (in-place)
(c) pixd != pixs1, (src1 | src2) --> input pixd
(3) For clarity, if the case is known, use these patterns:
(a) pixd = pixOr(NULL, pixs1, pixs2);
(b) pixOr(pixs1, pixs1, pixs2);
(c) pixOr(pixd, pixs1, pixs2);
(4) The size of the result is determined by pixs1.
(5) The depths of pixs1 and pixs2 must be equal.
(6) Note carefully that the order of pixs1 and pixs2 only matters
for the in-place case. For in-place, you must have
pixd == pixs1. Setting pixd == pixs2 gives an incorrect
result: the copy puts pixs1 image data in pixs2, and
the rasterop is then between pixs2 and pixs2 (a no-op).pixPaintSelfThroughMask
l_int32 pixPaintSelfThroughMask ( PIX *pixd, PIX *pixm, l_int32 x, l_int32 y, l_int32 tilesize, l_int32 searchdir )
pixPaintSelfThroughMask()
Input: pixd (8 bpp gray or 32 bpp rgb; not colormapped)
pixm (1 bpp mask)
x, y (origin of pixm relative to pixd; must not be negative)
tilesize (requested size for tiling)
searchdir (L_HORIZ, L_VERT)
Return: 0 if OK; 1 on error
Notes:
(1) In-place operation; pixd is changed.
(2) If pixm == NULL, it's a no-op.
(3) The mask origin is placed at (x,y) on pixd, and the
operation is clipped to the intersection of pixd and the
fg of the mask.
(4) The tilesize is the the requested size for tiling. The
actual size for each c.c. will be bounded by the minimum
dimension of the c.c. and the distance at which the tile
center is located.
(5) searchdir is the direction with respect to the b.b. of each
mask component, from which the square patch is chosen and
tiled onto the image, clipped by the mask component.
(6) Specifically, a mirrored tiling, generated from pixd,
is used to construct the pixels that are painted onto
pixd through pixm.pixPaintThroughMask
l_int32 pixPaintThroughMask ( PIX *pixd, PIX *pixm, l_int32 x, l_int32 y, l_uint32 val )
pixPaintThroughMask()
Input: pixd (1, 2, 4, 8, 16 or 32 bpp; or colormapped)
pixm (<optional> 1 bpp mask)
x, y (origin of pixm relative to pixd; can be negative)
val (pixel value to set at each masked pixel)
Return: 0 if OK; 1 on error
Notes:
(1) In-place operation. Calls pixSetMaskedCmap() for colormapped
images.
(2) For 1, 2, 4, 8 and 16 bpp gray, we take the appropriate
number of least significant bits of val.
(3) If pixm == NULL, it's a no-op.
(4) The mask origin is placed at (x,y) on pixd, and the
operation is clipped to the intersection of rectangles.
(5) For rgb, the components in val are in the canonical locations,
with red in location COLOR_RED, etc.
(6) Implementation detail 1:
For painting with val == 0 or val == maxval, you can use rasterop.
If val == 0, invert the mask so that it's 0 over the region
into which you want to write, and use PIX_SRC & PIX_DST to
clear those pixels. To write with val = maxval (all 1's),
use PIX_SRC | PIX_DST to set all bits under the mask.
(7) Implementation detail 2:
The rasterop trick can be used for depth > 1 as well.
For val == 0, generate the mask for depth d from the binary
mask using
pixmd = pixUnpackBinary(pixm, d, 1);
and use pixRasterop() with PIX_MASK. For val == maxval,
pixmd = pixUnpackBinary(pixm, d, 0);
and use pixRasterop() with PIX_PAINT.
But note that if d == 32 bpp, it is about 3x faster to use
the general implementation (not pixRasterop()).
(8) Implementation detail 3:
It might be expected that the switch in the inner loop will
cause large branching delays and should be avoided.
This is not the case, because the entrance is always the
same and the compiler can correctly predict the jump.pixSetMasked
l_int32 pixSetMasked ( PIX *pixd, PIX *pixm, l_uint32 val )
pixSetMasked()
Input: pixd (1, 2, 4, 8, 16 or 32 bpp; or colormapped)
pixm (<optional> 1 bpp mask; no operation if NULL)
val (value to set at each masked pixel)
Return: 0 if OK; 1 on error
Notes:
(1) In-place operation.
(2) NOTE: For cmapped images, this calls pixSetMaskedCmap().
@val must be the 32-bit color representation of the RGB pixel.
It is not the index into the colormap!
(2) If pixm == NULL, a warning is given.
(3) This is an implicitly aligned operation, where the UL
corners of pixd and pixm coincide. A warning is
issued if the two image sizes differ significantly,
but the operation proceeds.
(4) Each pixel in pixd that co-locates with an ON pixel
in pixm is set to the specified input value.
Other pixels in pixd are not changed.
(5) You can visualize this as painting the color through
the mask, as a stencil.
(6) If you do not want to have the UL corners aligned,
use the function pixSetMaskedGeneral(), which requires
you to input the UL corner of pixm relative to pixd.
(7) Implementation details: see comments in pixPaintThroughMask()
for when we use rasterop to do the painting.pixSetMaskedGeneral
l_int32 pixSetMaskedGeneral ( PIX *pixd, PIX *pixm, l_uint32 val, l_int32 x, l_int32 y )
pixSetMaskedGeneral()
Input: pixd (8, 16 or 32 bpp)
pixm (<optional> 1 bpp mask; no operation if null)
val (value to set at each masked pixel)
x, y (location of UL corner of pixm relative to pixd;
can be negative)
Return: 0 if OK; 1 on error
Notes:
(1) This is an in-place operation.
(2) Alignment is explicit. If you want the UL corners of
the two images to be aligned, use pixSetMasked().
(3) A typical use would be painting through the foreground
of a small binary mask pixm, located somewhere on a
larger pixd. Other pixels in pixd are not changed.
(4) You can visualize this as painting the color through
the mask, as a stencil.
(5) This uses rasterop to handle clipping and different depths of pixd.
(6) If pixd has a colormap, you should call pixPaintThroughMask().
(7) Why is this function here, if pixPaintThroughMask() does the
same thing, and does it more generally? I've retained it here
to show how one can paint through a mask using only full
image rasterops, rather than pixel peeking in pixm and poking
in pixd. It's somewhat baroque, but I found it amusing.pixSetUnderTransparency
PIX * pixSetUnderTransparency ( PIX *pixs, l_uint32 val, l_int32 debug )
pixSetUnderTransparency()
Input: pixs (32 bpp rgba)
val (32 bit unsigned color to use where alpha == 0)
debug (displays layers of pixs)
Return: pixd (32 bpp rgba), or null on error
Notes:
(1) This sets the r, g and b components under every fully
transparent alpha component to @val. The alpha components
are unchanged.
(2) Full transparency is denoted by alpha == 0. Setting
all pixels to a constant @val where alpha is transparent
can improve compressibility by reducing the entropy.
(3) The visual result depends on how the image is displayed.
(a) For display devices that respect the use of the alpha
layer, this will not affect the appearance.
(b) For typical leptonica operations, alpha is ignored,
so there will be a change in appearance because this
resets the rgb values in the fully transparent region.
(4) pixRead() and pixWrite() will, by default, read and write
4-component (rgba) pix in png format. To ignore the alpha
component after reading, or omit it on writing, pixSetSpp(..., 3).
(5) Here are some examples:
* To convert all fully transparent pixels in a 4 component
(rgba) png file to white:
pixs = pixRead(<infile>);
pixd = pixSetUnderTransparency(pixs, 0xffffff00, 0);
* To write pixd with the alpha component:
pixWrite(<outfile>, pixd, IFF_PNG);
* To write and rgba image without the alpha component, first do:
pixSetSpp(pixd, 3);
If you later want to use the alpha, spp must be reset to 4.
* (fancier) To remove the alpha by blending the image over
a white background:
pixRemoveAlpha()
This changes all pixel values where the alpha component is
not opaque (255).
(6) Caution. rgb images in leptonica typically have value 0 in
the alpha channel, which is fully transparent. If spp for
such an image were changed from 3 to 4, the image becomes
fully transparent, and this function will set each pixel to @val.
If you really want to set every pixel to the same value,
use pixSetAllArbitrary().
(7) This is useful for compressing an RGBA image where the part
of the image that is fully transparent is random junk; compression
is typically improved by setting that region to a constant.
For rendering as a 3 component RGB image over a uniform
background of arbitrary color, use pixAlphaBlendUniform().pixSubtract
PIX * pixSubtract ( PIX *pixd, PIX *pixs1, PIX *pixs2 )
pixSubtract()
Input: pixd (<optional>; this can be null, equal to pixs1,
equal to pixs2, or different from both pixs1 and pixs2)
pixs1 (can be == pixd)
pixs2 (can be == pixd)
Return: pixd always
Notes:
(1) This gives the set subtraction of two images with equal depth,
aligning them to the the UL corner. pixs1 and pixs2
need not have the same width and height.
(2) Source pixs2 is always subtracted from source pixs1.
The result is
pixs1 \ pixs2 = pixs1 & (~pixs2)
(3) There are 4 cases:
(a) pixd == null, (src1 - src2) --> new pixd
(b) pixd == pixs1, (src1 - src2) --> src1 (in-place)
(c) pixd == pixs2, (src1 - src2) --> src2 (in-place)
(d) pixd != pixs1 && pixd != pixs2),
(src1 - src2) --> input pixd
(4) For clarity, if the case is known, use these patterns:
(a) pixd = pixSubtract(NULL, pixs1, pixs2);
(b) pixSubtract(pixs1, pixs1, pixs2);
(c) pixSubtract(pixs2, pixs1, pixs2);
(d) pixSubtract(pixd, pixs1, pixs2);
(5) The size of the result is determined by pixs1.
(6) The depths of pixs1 and pixs2 must be equal.pixThresholdPixelSum
l_int32 pixThresholdPixelSum ( PIX *pix, l_int32 thresh, l_int32 *pabove, l_int32 *tab8 )
pixThresholdPixelSum()
Input: pix (1 bpp)
threshold
&above (<return> 1 if above threshold;
0 if equal to or less than threshold)
tab8 (<optional> 8-bit pixel lookup table)
Return: 0 if OK; 1 on error
Notes:
(1) This sums the ON pixels and returns immediately if the count
goes above threshold. It is therefore more efficient
for matching images (by running this function on the xor of
the 2 images) than using pixCountPixels(), which counts all
pixels before returning.pixVarianceByColumn
NUMA * pixVarianceByColumn ( PIX *pix, BOX *box )
pixVarianceByColumn()
Input: pix (8 or 16 bpp; no colormap)
box (<optional> clipping box for variance; can be null)
Return: na of rmsdev by column, or null on error
Notes:
(1) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.
(2) We are actually computing the RMS deviation in each row.
This is the square root of the variance.pixVarianceByRow
NUMA * pixVarianceByRow ( PIX *pix, BOX *box )
pixVarianceByRow()
Input: pix (8 or 16 bpp; no colormap)
box (<optional> clipping box for variance; can be null)
Return: na of rmsdev by row, or null on error
Notes:
(1) To resample for a bin size different from 1, use
numaUniformSampling() on the result of this function.
(2) We are actually computing the RMS deviation in each row.
This is the square root of the variance.pixVarianceInRect
l_int32 pixVarianceInRect ( PIX *pix, BOX *box, l_float32 *prootvar )
pixVarianceInRect()
Input: pix (1, 2, 4, 8 bpp; not cmapped)
box (<optional> if null, use entire image)
&rootvar (<return> sqrt variance of pixel values in region)
Return: 0 if OK; 1 on errorpixXor
PIX * pixXor ( PIX *pixd, PIX *pixs1, PIX *pixs2 )
pixXor()
Input: pixd (<optional>; this can be null, equal to pixs1,
different from pixs1)
pixs1 (can be == pixd)
pixs2 (must be != pixd)
Return: pixd always
Notes:
(1) This gives the XOR of two images with equal depth,
aligning them to the the UL corner. pixs1 and pixs2
need not have the same width and height.
(2) There are 3 cases:
(a) pixd == null, (src1 ^ src2) --> new pixd
(b) pixd == pixs1, (src1 ^ src2) --> src1 (in-place)
(c) pixd != pixs1, (src1 ^ src2) --> input pixd
(3) For clarity, if the case is known, use these patterns:
(a) pixd = pixXor(NULL, pixs1, pixs2);
(b) pixXor(pixs1, pixs1, pixs2);
(c) pixXor(pixd, pixs1, pixs2);
(4) The size of the result is determined by pixs1.
(5) The depths of pixs1 and pixs2 must be equal.
(6) Note carefully that the order of pixs1 and pixs2 only matters
for the in-place case. For in-place, you must have
pixd == pixs1. Setting pixd == pixs2 gives an incorrect
result: the copy puts pixs1 image data in pixs2, and
the rasterop is then between pixs2 and pixs2 (a no-op).pixZero
l_int32 pixZero ( PIX *pix, l_int32 *pempty )
pixZero()
Input: pix (all depths; not colormapped)
&empty (<return> 1 if all bits in image are 0; 0 otherwise)
Return: 0 if OK; 1 on error
Notes:
(1) For a binary image, if there are no fg (black) pixels, empty = 1.
(2) For a grayscale image, if all pixels are black (0), empty = 1.
(3) For an RGB image, if all 4 components in every pixel is 0,
empty = 1.pixaCountPixels
NUMA * pixaCountPixels ( PIXA *pixa )
pixaCountPixels()
Input: pixa (array of 1 bpp pix)
Return: na of ON pixels in each pix, or null on errorAUTHOR
Zakariyya Mughal <zmughal@cpan.org>
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.