# NAME

Image::Leptonica::Func::boxfunc3

# VERSION

version 0.04

`boxfunc3.c`

```
boxfunc3.c
Boxa/Boxaa painting into pix
PIX *pixMaskConnComp()
PIX *pixMaskBoxa()
PIX *pixPaintBoxa()
PIX *pixSetBlackOrWhiteBoxa()
PIX *pixPaintBoxaRandom()
PIX *pixBlendBoxaRandom()
PIX *pixDrawBoxa()
PIX *pixDrawBoxaRandom()
PIX *boxaaDisplay()
Split mask components into Boxa
BOXA *pixSplitIntoBoxa()
BOXA *pixSplitComponentIntoBoxa()
static l_int32 pixSearchForRectangle()
Comparison between boxa
l_int32 boxaCompareRegions()
See summary in pixPaintBoxa() of various ways to paint and draw
boxes on images.
```

# FUNCTIONS

## boxaCompareRegions

l_int32 boxaCompareRegions ( BOXA *boxa1, BOXA *boxa2, l_int32 areathresh, l_int32 *pnsame, l_float32 *pdiffarea, l_float32 *pdiffxor, PIX **ppixdb )

```
boxaCompareRegions()
Input: boxa1, boxa2
areathresh (minimum area of boxes to be considered)
&pnsame (<return> true if same number of boxes)
&pdiffarea (<return> fractional difference in total area)
&pdiffxor (<optional return> fractional difference
in xor of regions)
&pixdb (<optional return> debug pix showing two boxa)
Return: 0 if OK, 1 on error
Notes:
(1) This takes 2 boxa, removes all boxes smaller than a given area,
and compares the remaining boxes between the boxa.
(2) The area threshold is introduced to help remove noise from
small components. Any box with a smaller value of w * h
will be removed from consideration.
(3) The xor difference is the most stringent test, requiring alignment
of the corresponding boxes. It is also more computationally
intensive and is optionally returned. Alignment is to the
UL corner of each region containing all boxes, as given by
boxaGetExtent().
(4) Both fractional differences are with respect to the total
area in the two boxa. They range from 0.0 to 1.0.
A perfect match has value 0.0. If both boxa are empty,
we return 0.0; if one is empty we return 1.0.
(5) An example input might be the rectangular regions of a
segmentation mask for text or images from two pages.
```

## boxaaDisplay

PIX * boxaaDisplay ( BOXAA *baa, l_int32 linewba, l_int32 linewb, l_uint32 colorba, l_uint32 colorb, l_int32 w, l_int32 h )

```
boxaaDisplay()
Input: baa
linewba (line width to display boxa)
linewb (line width to display box)
colorba (color to display boxa)
colorb (color to display box)
w (of pix; use 0 if determined by baa)
h (of pix; use 0 if determined by baa)
Return: 0 if OK, 1 on error
```

## pixBlendBoxaRandom

PIX * pixBlendBoxaRandom ( PIX *pixs, BOXA *boxa, l_float32 fract )

```
pixBlendBoxaRandom()
Input: pixs (any depth; can be cmapped)
boxa (of boxes, to blend/paint)
fract (of box color to use)
Return: pixd (32 bpp, with blend/painted boxes), or null on error
Notes:
(1) pixs is converted to 32 bpp.
(2) This differs from pixPaintBoxaRandom(), in that the
colors here are blended with the color of pixs.
(3) We use up to 254 different colors for painting the regions.
(4) If boxes overlap, the final color depends only on the last
rect that is used.
```

## pixDrawBoxa

PIX * pixDrawBoxa ( PIX *pixs, BOXA *boxa, l_int32 width, l_uint32 val )

```
pixDrawBoxa()
Input: pixs (any depth; can be cmapped)
boxa (of boxes, to draw)
width (of lines)
val (rgba color to draw)
Return: pixd (with outlines of boxes added), or null on error
Notes:
(1) If pixs is 1 bpp or is colormapped, it is converted to 8 bpp
and the boxa is drawn using a colormap; otherwise,
it is converted to 32 bpp rgb.
```

## pixDrawBoxaRandom

PIX * pixDrawBoxaRandom ( PIX *pixs, BOXA *boxa, l_int32 width )

```
pixDrawBoxaRandom()
Input: pixs (any depth, can be cmapped)
boxa (of boxes, to draw)
width (thickness of line)
Return: pixd (with box outlines drawn), or null on error
Notes:
(1) If pixs is 1 bpp, we draw the boxa using a colormap;
otherwise, we convert to 32 bpp.
(2) We use up to 254 different colors for drawing the boxes.
(3) If boxes overlap, the later ones draw over earlier ones.
```

## pixMaskBoxa

PIX * pixMaskBoxa ( PIX *pixd, PIX *pixs, BOXA *boxa, l_int32 op )

```
pixMaskBoxa()
Input: pixd (<optional> may be null)
pixs (any depth; not cmapped)
boxa (of boxes, to paint)
op (L_SET_PIXELS, L_CLEAR_PIXELS, L_FLIP_PIXELS)
Return: pixd (with masking op over the boxes), or null on error
Notes:
(1) This can be used with:
pixd = NULL (makes a new pixd)
pixd = pixs (in-place)
(2) If pixd == NULL, this first makes a copy of pixs, and then
bit-twiddles over the boxes. Otherwise, it operates directly
on pixs.
(3) This simple function is typically used with 1 bpp images.
It uses the 1-image rasterop function, rasteropUniLow(),
to set, clear or flip the pixels in pixd.
(4) If you want to generate a 1 bpp mask of ON pixels from the boxes
in a Boxa, in a pix of size (w,h):
pix = pixCreate(w, h, 1);
pixMaskBoxa(pix, pix, boxa, L_SET_PIXELS);
```

## pixMaskConnComp

PIX * pixMaskConnComp ( PIX *pixs, l_int32 connectivity, BOXA **pboxa )

```
pixMaskConnComp()
Input: pixs (1 bpp)
connectivity (4 or 8)
&boxa (<optional return> bounding boxes of c.c.)
Return: pixd (1 bpp mask over the c.c.), or null on error
Notes:
(1) This generates a mask image with ON pixels over the
b.b. of the c.c. in pixs. If there are no ON pixels in pixs,
pixd will also have no ON pixels.
```

## pixPaintBoxa

PIX * pixPaintBoxa ( PIX *pixs, BOXA *boxa, l_uint32 val )

```
pixPaintBoxa()
Input: pixs (any depth, can be cmapped)
boxa (of boxes, to paint)
val (rgba color to paint)
Return: pixd (with painted boxes), or null on error
Notes:
(1) If pixs is 1 bpp or is colormapped, it is converted to 8 bpp
and the boxa is painted using a colormap; otherwise,
it is converted to 32 bpp rgb.
(2) There are several ways to display a box on an image:
* Paint it as a solid color
* Draw the outline
* Blend the outline or region with the existing image
We provide painting and drawing here; blending is in blend.c.
When painting or drawing, the result can be either a
cmapped image or an rgb image. The dest will be cmapped
if the src is either 1 bpp or has a cmap that is not full.
To force RGB output, use pixConvertTo8(pixs, FALSE)
before calling any of these paint and draw functions.
```

## pixPaintBoxaRandom

PIX * pixPaintBoxaRandom ( PIX *pixs, BOXA *boxa )

```
pixPaintBoxaRandom()
Input: pixs (any depth, can be cmapped)
boxa (of boxes, to paint)
Return: pixd (with painted boxes), or null on error
Notes:
(1) If pixs is 1 bpp, we paint the boxa using a colormap;
otherwise, we convert to 32 bpp.
(2) We use up to 254 different colors for painting the regions.
(3) If boxes overlap, the later ones paint over earlier ones.
```

## pixSetBlackOrWhiteBoxa

PIX * pixSetBlackOrWhiteBoxa ( PIX *pixs, BOXA *boxa, l_int32 op )

```
pixSetBlackOrWhiteBoxa()
Input: pixs (any depth, can be cmapped)
boxa (<optional> of boxes, to clear or set)
op (L_SET_BLACK, L_SET_WHITE)
Return: pixd (with boxes filled with white or black), or null on error
```

## pixSplitComponentIntoBoxa

BOXA * pixSplitComponentIntoBoxa ( PIX *pix, BOX *box, l_int32 minsum, l_int32 skipdist, l_int32 delta, l_int32 maxbg, l_int32 maxcomps, l_int32 remainder )

```
pixSplitComponentIntoBoxa()
Input: pixs (1 bpp)
box (<optional> location of pixs w/rt an origin)
minsum (minimum pixels to trigger propagation)
skipdist (distance before computing sum for propagation)
delta (difference required to stop propagation)
maxbg (maximum number of allowed bg pixels in ref scan)
maxcomps (use 0 for unlimited number of subdivided components)
remainder (set to 1 to get b.b. of remaining stuff)
Return: boxa (of rectangles covering the fg of pixs), or null on error
Notes:
(1) This generates a boxa of rectangles that covers
the fg of a mask. It does so by a greedy partitioning of
the mask, choosing the largest rectangle found from
each of the four directions at each step.
(2) The input parameters give some flexibility for boundary
noise. The resulting set of rectangles must cover all
the fg pixels and, in addition, may cover some bg pixels.
Using small input parameters on a noiseless mask (i.e., one
that has only large vertical and horizontal edges) will
result in a proper covering of only the fg pixels of the mask.
(3) The input is assumed to be a single connected component, that
may have holes. From each side, sweep inward, counting
the pixels. If the count becomes greater than @minsum,
and we have moved forward a further amount @skipdist,
record that count ('countref'), but don't accept if the scan
contains more than @maxbg bg pixels. Continue the scan
until we reach a count that differs from countref by at
least @delta, at which point the propagation stops. The box
swept out gets a score, which is the sum of fg pixels
minus a penalty. The penalty is the number of bg pixels
in the box. This is done from all four sides, and the
side with the largest score is saved as a rectangle.
The process repeats until there is either no rectangle
left, or there is one that can't be captured from any
direction. For the latter case, we simply accept the
last rectangle.
(4) The input box is only used to specify the location of
the UL corner of pixs, with respect to an origin that
typically represents the UL corner of an underlying image,
of which pixs is one component. If @box is null,
the UL corner is taken to be (0, 0).
(5) The parameter @maxcomps gives the maximum number of allowed
rectangles extracted from any single connected component.
Use 0 if no limit is to be applied.
(6) The flag @remainder specifies whether we take a final bounding
box for anything left after the maximum number of allowed
rectangle is extracted.
(7) So if @maxcomps > 0, it specifies that we want no more than
the first @maxcomps rectangles that satisfy the input
criteria. After this, we can get a final rectangle that
bounds everything left over by setting @remainder == 1.
If @remainder == 0, we only get rectangles that satisfy
the input criteria.
(8) It should be noted that the removal of rectangles can
break the original c.c. into several c.c.
(9) Summing up:
* If @maxcomp == 0, the splitting proceeds as far as possible.
* If @maxcomp > 0, the splitting stops when @maxcomps are
found, or earlier if no more components can be selected.
* If @remainder == 1 and components remain that cannot be
selected, they are returned as a single final rectangle;
otherwise, they are ignored.
```

## pixSplitIntoBoxa

BOXA * pixSplitIntoBoxa ( PIX *pixs, l_int32 minsum, l_int32 skipdist, l_int32 delta, l_int32 maxbg, l_int32 maxcomps, l_int32 remainder )

```
pixSplitIntoBoxa()
Input: pixs (1 bpp)
minsum (minimum pixels to trigger propagation)
skipdist (distance before computing sum for propagation)
delta (difference required to stop propagation)
maxbg (maximum number of allowed bg pixels in ref scan)
maxcomps (use 0 for unlimited number of subdivided components)
remainder (set to 1 to get b.b. of remaining stuff)
Return: boxa (of rectangles covering the fg of pixs), or null on error
Notes:
(1) This generates a boxa of rectangles that covers
the fg of a mask. For each 8-connected component in pixs,
it does a greedy partitioning, choosing the largest
rectangle found from each of the four directions at each iter.
See pixSplitComponentIntoBoxa() for details.
(2) The input parameters give some flexibility for boundary
noise. The resulting set of rectangles may cover some
bg pixels.
(3) This should be used when there are a small number of
mask components, each of which has sides that are close
to horizontal and vertical. The input parameters @delta
and @maxbg determine whether or not holes in the mask are covered.
(4) The parameter @maxcomps gives the maximum number of allowed
rectangles extracted from any single connected component.
Use 0 if no limit is to be applied.
(5) The flag @remainder specifies whether we take a final bounding
box for anything left after the maximum number of allowed
rectangle is extracted.
```

# AUTHOR

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.