NAME
Image::Leptonica::Func::pix1
VERSION
version 0.04
pix1.c
pix1.c
The pixN.c {N = 1,2,3,4,5} files are sorted by the type of operation.
The primary functions in these files are:
pix1.c: constructors, destructors and field accessors
pix2.c: pixel poking of image, pad and border pixels
pix3.c: masking and logical ops, counting, mirrored tiling
pix4.c: histograms, statistics, fg/bg estimation
pix5.c: property measurements, rectangle extraction
This file has the basic constructors, destructors and field accessors
Pix memory management (allows custom allocator and deallocator)
static void *pix_malloc()
static void pix_free()
void setPixMemoryManager()
Pix creation
PIX *pixCreate()
PIX *pixCreateNoInit()
PIX *pixCreateTemplate()
PIX *pixCreateTemplateNoInit()
PIX *pixCreateHeader()
PIX *pixClone()
Pix destruction
void pixDestroy()
static void pixFree()
Pix copy
PIX *pixCopy()
l_int32 pixResizeImageData()
l_int32 pixCopyColormap()
l_int32 pixSizesEqual()
l_int32 pixTransferAllData()
l_int32 pixSwapAndDestroy()
Pix accessors
l_int32 pixGetWidth()
l_int32 pixSetWidth()
l_int32 pixGetHeight()
l_int32 pixSetHeight()
l_int32 pixGetDepth()
l_int32 pixSetDepth()
l_int32 pixGetDimensions()
l_int32 pixSetDimensions()
l_int32 pixCopyDimensions()
l_int32 pixGetSpp()
l_int32 pixSetSpp()
l_int32 pixCopySpp()
l_int32 pixGetWpl()
l_int32 pixSetWpl()
l_int32 pixGetRefcount()
l_int32 pixChangeRefcount()
l_uint32 pixGetXRes()
l_int32 pixSetXRes()
l_uint32 pixGetYRes()
l_int32 pixSetYRes()
l_int32 pixGetResolution()
l_int32 pixSetResolution()
l_int32 pixCopyResolution()
l_int32 pixScaleResolution()
l_int32 pixGetInputFormat()
l_int32 pixSetInputFormat()
l_int32 pixCopyInputFormat()
char *pixGetText()
l_int32 pixSetText()
l_int32 pixAddText()
l_int32 pixCopyText()
PIXCMAP *pixGetColormap()
l_int32 pixSetColormap()
l_int32 pixDestroyColormap()
l_uint32 *pixGetData()
l_int32 pixSetData()
l_uint32 *pixExtractData()
l_int32 pixFreeData()
Pix line ptrs
void **pixGetLinePtrs()
Pix debug
l_int32 pixPrintStreamInfo()
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Important notes on direct management of pix image data
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Custom allocator and deallocator
--------------------------------
At the lowest level, you can specify the function that does the
allocation and deallocation of the data field in the pix.
By default, this is malloc and free. However, by calling
setPixMemoryManager(), custom functions can be substituted.
When using this, keep two things in mind:
(1) Call setPixMemoryManager() before any pix have been allocated
(2) Destroy all pix as usual, in order to prevent leaks.
In pixalloc.c, we provide an example custom allocator and deallocator.
To use it, you must call pmsCreate() before any pix have been allocated
and pmsDestroy() at the end after all pix have been destroyed.
Direct manipulation of the pix data field
-----------------------------------------
Memory management of the (image) data field in the pix is
handled differently from that in the colormap or text fields.
For colormap and text, the functions pixSetColormap() and
pixSetText() remove the existing heap data and insert the
new data. For the image data, pixSetData() just reassigns the
data field; any existing data will be lost if there isn't
another handle for it.
Why is pixSetData() limited in this way? Because the image
data can be very large, we need flexible ways to handle it,
particularly when you want to re-use the data in a different
context without making a copy. Here are some different
things you might want to do:
(1) Use pixCopy(pixd, pixs) where pixd is not the same size
as pixs. This will remove the data in pixd, allocate a
new data field in pixd, and copy the data from pixs, leaving
pixs unchanged.
(2) Use pixTransferAllData(pixd, &pixs, ...) to transfer the
data from pixs to pixd without making a copy of it. If
pixs is not cloned, this will do the transfer and destroy pixs.
But if the refcount of pixs is greater than 1, it just copies
the data and decrements the ref count.
(3) Use pixSwapAndDestroy(pixd, &pixs) to replace pixs by an
existing pixd. This is similar to pixTransferAllData(), but
simpler, in that it never makes any copies and if pixs is
cloned, the other references are not changed by this operation.
(4) Use pixExtractData() to extract the image data from the pix
without copying if possible. This could be used, for example,
to convert from a pix to some other data structure with minimal
heap allocation. After the data is extracated, the pixels can
be munged and used in another context. However, the danger
here is that the pix might have a refcount > 1, in which case
a copy of the data must be made and the input pix left unchanged.
If there are no clones, the image data can be extracted without
a copy, and the data ptr in the pix must be nulled before
destroying it because the pix will no longer 'own' the data.
We have provided accessors and functions here that should be
sufficient so that you can do anything you want without
explicitly referencing any of the pix member fields.
However, to avoid memory smashes and leaks when doing special operations
on the pix data field, look carefully at the behavior of the image
data accessors and keep in mind that when you invoke pixDestroy(),
the pix considers itself the owner of all its heap data.FUNCTIONS
pixAddText
l_int32 pixAddText ( PIX *pix, const char *textstring )
pixAddText()
Input: pix
textstring
Return: 0 if OK, 1 on error
Notes:
(1) This adds the new textstring to any existing text.
(2) Either or both the existing text and the new text
string can be null.pixClone
PIX * pixClone ( PIX *pixs )
pixClone()
Input: pix
Return: same pix (ptr), or null on error
Notes:
(1) A "clone" is simply a handle (ptr) to an existing pix.
It is implemented because (a) images can be large and
hence expensive to copy, and (b) extra handles to a data
structure need to be made with a simple policy to avoid
both double frees and memory leaks. Pix are reference
counted. The side effect of pixClone() is an increase
by 1 in the ref count.
(2) The protocol to be used is:
(a) Whenever you want a new handle to an existing image,
call pixClone(), which just bumps a ref count.
(b) Always call pixDestroy() on all handles. This
decrements the ref count, nulls the handle, and
only destroys the pix when pixDestroy() has been
called on all handles.pixCopy
PIX * pixCopy ( PIX *pixd, PIX *pixs )
pixCopy()
Input: pixd (<optional>; can be null, or equal to pixs,
or different from pixs)
pixs
Return: pixd, or null on error
Notes:
(1) There are three cases:
(a) pixd == null (makes a new pix; refcount = 1)
(b) pixd == pixs (no-op)
(c) pixd != pixs (data copy; no change in refcount)
If the refcount of pixd > 1, case (c) will side-effect
these handles.
(2) The general pattern of use is:
pixd = pixCopy(pixd, pixs);
This will work for all three cases.
For clarity when the case is known, you can use:
(a) pixd = pixCopy(NULL, pixs);
(c) pixCopy(pixd, pixs);
(3) For case (c), we check if pixs and pixd are the same
size (w,h,d). If so, the data is copied directly.
Otherwise, the data is reallocated to the correct size
and the copy proceeds. The refcount of pixd is unchanged.
(4) This operation, like all others that may involve a pre-existing
pixd, will side-effect any existing clones of pixd.pixCopyColormap
l_int32 pixCopyColormap ( PIX *pixd, PIX *pixs )
pixCopyColormap()
Input: src and dest Pix
Return: 0 if OK, 1 on error
Notes:
(1) This always destroys any colormap in pixd (except if
the operation is a no-op.pixCopyDimensions
l_int32 pixCopyDimensions ( PIX *pixd, PIX *pixs )
pixCopyDimensions()
Input: pixd
pixd
Return: 0 if OK, 1 on errorpixCopySpp
l_int32 pixCopySpp ( PIX *pixd, PIX *pixs )
pixCopySpp()
Input: pixd
pixs
Return: 0 if OK, 1 on errorpixCreate
PIX * pixCreate ( l_int32 width, l_int32 height, l_int32 depth )
pixCreate()
Input: width, height, depth
Return: pixd (with data allocated and initialized to 0),
or null on errorpixCreateHeader
PIX * pixCreateHeader ( l_int32 width, l_int32 height, l_int32 depth )
pixCreateHeader()
Input: width, height, depth
Return: pixd (with no data allocated), or null on error
Notes:
(1) It is assumed that all 32 bit pix have 3 spp. If there is
a valid alpha channel, this will be set to 4 spp later.
(2) If the number of bytes to be allocated is larger than the
maximum value in an int32, we can get overflow, resulting
in a smaller amount of memory actually being allocated.
Later, an attempt to access memory that wasn't allocated will
cause a crash. So to avoid crashing a program (or worse)
with bad (or malicious) input, this is where we limit the
requested allocation of image data in a typesafe way.pixCreateNoInit
PIX * pixCreateNoInit ( l_int32 width, l_int32 height, l_int32 depth )
pixCreateNoInit()
Input: width, height, depth
Return: pixd (with data allocated but not initialized),
or null on error
Notes:
(1) Must set pad bits to avoid reading unitialized data, because
some optimized routines (e.g., pixConnComp()) read from pad bits.pixCreateTemplate
PIX * pixCreateTemplate ( PIX *pixs )
pixCreateTemplate()
Input: pixs
Return: pixd, or null on error
Notes:
(1) Makes a Pix of the same size as the input Pix, with the
data array allocated and initialized to 0.
(2) Copies the other fields, including colormap if it exists.pixCreateTemplateNoInit
PIX * pixCreateTemplateNoInit ( PIX *pixs )
pixCreateTemplateNoInit()
Input: pixs
Return: pixd, or null on error
Notes:
(1) Makes a Pix of the same size as the input Pix, with
the data array allocated but not initialized to 0.
(2) Copies the other fields, including colormap if it exists.pixDestroy
void pixDestroy ( PIX **ppix )
pixDestroy()
Input: &pix <will be nulled>
Return: void
Notes:
(1) Decrements the ref count and, if 0, destroys the pix.
(2) Always nulls the input ptr.pixDestroyColormap
l_int32 pixDestroyColormap ( PIX *pix )
pixDestroyColormap()
Input: pix
Return: 0 if OK, 1 on errorpixExtractData
l_uint32 * pixExtractData ( PIX *pixs )
pixExtractData()
Notes:
(1) This extracts the pix image data for use in another context.
The caller still needs to use pixDestroy() on the input pix.
(2) If refcount == 1, the data is extracted and the
pix->data ptr is set to NULL.
(3) If refcount > 1, this simply returns a copy of the data,
using the pix allocator, and leaving the input pix unchanged.pixFreeData
l_int32 pixFreeData ( PIX *pix )
pixFreeData()
Notes:
(1) This frees the data and sets the pix data ptr to null.
It should be used before pixSetData() in the situation where
you want to free any existing data before doing
a subsequent assignment with pixSetData().pixGetData
l_uint32 * pixGetData ( PIX *pix )
pixGetData()
Notes:
(1) This gives a new handle for the data. The data is still
owned by the pix, so do not call FREE() on it.pixGetDimensions
l_int32 pixGetDimensions ( PIX *pix, l_int32 *pw, l_int32 *ph, l_int32 *pd )
pixGetDimensions()
Input: pix
&w, &h, &d (<optional return>; each can be null)
Return: 0 if OK, 1 on errorpixGetLinePtrs
void ** pixGetLinePtrs ( PIX *pix, l_int32 *psize )
pixGetLinePtrs()
Input: pix
&size (<optional return> array size, which is the pix height)
Return: array of line ptrs, or null on error
Notes:
(1) This is intended to be used for fast random pixel access.
For example, for an 8 bpp image,
val = GET_DATA_BYTE(lines8[i], j);
is equivalent to, but much faster than,
pixGetPixel(pix, j, i, &val);
(2) How much faster? For 1 bpp, it's from 6 to 10x faster.
For 8 bpp, it's an amazing 30x faster. So if you are
doing random access over a substantial part of the image,
use this line ptr array.
(3) When random access is used in conjunction with a stack,
queue or heap, the overall computation time depends on
the operations performed on each struct that is popped
or pushed, and whether we are using a priority queue (O(logn))
or a queue or stack (O(1)). For example, for maze search,
the overall ratio of time for line ptrs vs. pixGet/Set* is
Maze type Type Time ratio
binary queue 0.4
gray heap (priority queue) 0.6
(4) Because this returns a void** and the accessors take void*,
the compiler cannot check the pointer types. It is
strongly recommended that you adopt a naming scheme for
the returned ptr arrays that indicates the pixel depth.
(This follows the original intent of Simonyi's "Hungarian"
application notation, where naming is used proactively
to make errors visibly obvious.) By doing this, you can
tell by inspection if the correct accessor is used.
For example, for an 8 bpp pixg:
void **lineg8 = pixGetLinePtrs(pixg, NULL);
val = GET_DATA_BYTE(lineg8[i], j); // fast access; BYTE, 8
...
FREE(lineg8); // don't forget this
(5) These are convenient for accessing bytes sequentially in an
8 bpp grayscale image. People who write image processing code
on 8 bpp images are accustomed to grabbing pixels directly out
of the raster array. Note that for little endians, you first
need to reverse the byte order in each 32-bit word.
Here's a typical usage pattern:
pixEndianByteSwap(pix); // always safe; no-op on big-endians
l_uint8 **lineptrs = (l_uint8 **)pixGetLinePtrs(pix, NULL);
pixGetDimensions(pix, &w, &h, NULL);
for (i = 0; i < h; i++) {
l_uint8 *line = lineptrs[i];
for (j = 0; j < w; j++) {
val = line[j];
...
}
}
pixEndianByteSwap(pix); // restore big-endian order
FREE(lineptrs);
This can be done even more simply as follows:
l_uint8 **lineptrs = pixSetupByteProcessing(pix, &w, &h);
for (i = 0; i < h; i++) {
l_uint8 *line = lineptrs[i];
for (j = 0; j < w; j++) {
val = line[j];
...
}
}
pixCleanupByteProcessing(pix, lineptrs);pixGetResolution
l_int32 pixGetResolution ( PIX *pix, l_int32 *pxres, l_int32 *pyres )
pixGetResolution()
Input: pix
&xres, &yres (<optional return>; each can be null)
Return: 0 if OK, 1 on errorpixGetText
char * pixGetText ( PIX *pix )
pixGetText()
Input: pix
Return: ptr to existing text string
Notes:
(1) The text string belongs to the pix. The caller must
NOT free it!pixPrintStreamInfo
l_int32 pixPrintStreamInfo ( FILE *fp, PIX *pix, const char *text )
pixPrintStreamInfo()
Input: fp (file stream)
pix
text (<optional> identifying string; can be null)
Return: 0 if OK, 1 on errorpixResizeImageData
l_int32 pixResizeImageData ( PIX *pixd, PIX *pixs )
pixResizeImageData()
Input: pixd (gets new uninitialized buffer for image data)
pixs (determines the size of the buffer; not changed)
Return: 0 if OK, 1 on error
Notes:
(1) This removes any existing image data from pixd and
allocates an uninitialized buffer that will hold the
amount of image data that is in pixs.pixSetColormap
l_int32 pixSetColormap ( PIX *pix, PIXCMAP *colormap )
pixSetColormap()
Input: pix
colormap (to be assigned)
Return: 0 if OK, 1 on error.
Notes:
(1) Unlike with the pix data field, pixSetColormap() destroys
any existing colormap before assigning the new one.
Because colormaps are not ref counted, it is important that
the new colormap does not belong to any other pix.pixSetData
l_int32 pixSetData ( PIX *pix, l_uint32 *data )
pixSetData()
Notes:
(1) This does not free any existing data. To free existing
data, use pixFreeData() before pixSetData().pixSetDimensions
l_int32 pixSetDimensions ( PIX *pix, l_int32 w, l_int32 h, l_int32 d )
pixSetDimensions()
Input: pix
w, h, d (use 0 to skip the setting for any of these)
Return: 0 if OK, 1 on errorpixSetResolution
l_int32 pixSetResolution ( PIX *pix, l_int32 xres, l_int32 yres )
pixSetResolution()
Input: pix
xres, yres (use 0 to skip the setting for either of these)
Return: 0 if OK, 1 on errorpixSetSpp
l_int32 pixSetSpp ( PIX *pix, l_int32 spp )
pixSetSpp()
Input: pix
spp (1, 3 or 4)
Return: 0 if OK, 1 on error
Notes:
(1) For a 32 bpp pix, this can be used to ignore the
alpha sample (spp == 3) or to use it (spp == 4).
For example, to write a spp == 4 image without the alpha
sample (as an rgb pix), call pixSetSpp(pix, 3) and
then write it out as a png.pixSetText
l_int32 pixSetText ( PIX *pix, const char *textstring )
pixSetText()
Input: pix
textstring (can be null)
Return: 0 if OK, 1 on error
Notes:
(1) This removes any existing textstring and puts a copy of
the input textstring there.pixSizesEqual
l_int32 pixSizesEqual ( PIX *pix1, PIX *pix2 )
pixSizesEqual()
Input: two pix
Return: 1 if the two pix have same {h, w, d}; 0 otherwise.pixSwapAndDestroy
l_int32 pixSwapAndDestroy ( PIX **ppixd, PIX **ppixs )
pixSwapAndDestroy()
Input: &pixd (<optional, return> input pixd can be null,
and it must be different from pixs)
&pixs (will be nulled after the swap)
Return: 0 if OK, 1 on error
Notes:
(1) Simple operation to change the handle name safely.
After this operation, the original image in pixd has
been destroyed, pixd points to what was pixs, and
the input pixs ptr has been nulled.
(2) This works safely whether or not pixs and pixd are cloned.
If pixs is cloned, the other handles still point to
the original image, with the ref count reduced by 1.
(3) Usage example:
Pix *pix1 = pixRead("...");
Pix *pix2 = function(pix1, ...);
pixSwapAndDestroy(&pix1, &pix2);
pixDestroy(&pix1); // holds what was in pix2
Example with clones ([] shows ref count of image generated
by the function):
Pix *pixs = pixRead("...");
Pix *pix1 = pixClone(pixs);
Pix *pix2 = function(pix1, ...); [1]
Pix *pix3 = pixClone(pix2); [1] --> [2]
pixSwapAndDestroy(&pix1, &pix2);
pixDestroy(&pixs); // still holds read image
pixDestroy(&pix1); // holds what was in pix2 [2] --> [1]
pixDestroy(&pix3); // holds what was in pix2 [1] --> [0]pixTransferAllData
l_int32 pixTransferAllData ( PIX *pixd, PIX **ppixs, l_int32 copytext, l_int32 copyformat )
pixTransferAllData()
Input: pixd (must be different from pixs)
&pixs (will be nulled if refcount goes to 0)
copytext (1 to copy the text field; 0 to skip)
copyformat (1 to copy the informat field; 0 to skip)
Return: 0 if OK, 1 on error
Notes:
(1) This does a complete data transfer from pixs to pixd,
followed by the destruction of pixs (refcount permitting).
(2) If the refcount of pixs is 1, pixs is destroyed. Otherwise,
the data in pixs is copied (rather than transferred) to pixd.
(3) This operation, like all others with a pre-existing pixd,
will side-effect any existing clones of pixd. The pixd
refcount does not change.
(4) When might you use this? Suppose you have an in-place Pix
function (returning void) with the typical signature:
void function-inplace(PIX *pix, ...)
where "..." are non-pointer input parameters, and suppose
further that you sometimes want to return an arbitrary Pix
in place of the input Pix. There are two ways you can do this:
(a) The straightforward way is to change the function
signature to take the address of the Pix ptr:
void function-inplace(PIX **ppix, ...) {
PIX *pixt = function-makenew(*ppix);
pixDestroy(ppix);
*ppix = pixt;
return;
}
Here, the input and returned pix are different, as viewed
by the calling function, and the inplace function is
expected to destroy the input pix to avoid a memory leak.
(b) Keep the signature the same and use pixTransferAllData()
to return the new Pix in the input Pix struct:
void function-inplace(PIX *pix, ...) {
PIX *pixt = function-makenew(pix);
pixTransferAllData(pix, &pixt, 0, 0);
// pixDestroy() is called on pixt
return;
}
Here, the input and returned pix are the same, as viewed
by the calling function, and the inplace function must
never destroy the input pix, because the calling function
maintains an unchanged handle to it.setPixMemoryManager
void setPixMemoryManager ( void * ( ( *allocator ) ( size_t ) ), void ( ( *deallocator ) ( void * ) ) )
setPixMemoryManager()
Input: allocator (<optional>; use null to skip)
deallocator (<optional>; use null to skip)
Return: void
Notes:
(1) Use this to change the alloc and/or dealloc functions;
e.g., setPixMemoryManager(my_malloc, my_free).
(2) The C99 standard (section 6.7.5.3, par. 8) says:
A declaration of a parameter as "function returning type"
shall be adjusted to "pointer to function returning type"
so that it can be in either of these two forms:
(a) type (function-ptr(type, ...))
(b) type ((*function-ptr)(type, ...))
because form (a) is implictly converted to form (b), as in the
definition of struct PixMemoryManager above. So, for example,
we should be able to declare either of these:
(a) void *(allocator(size_t))
(b) void *((*allocator)(size_t))
However, MSVC++ only accepts the second version.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.