Image::Leptonica::Func::pix1
version 0.03
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.
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.
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.
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.
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.
l_int32 pixCopyDimensions ( PIX *pixd, PIX *pixs )
pixCopyDimensions() Input: pixd pixd Return: 0 if OK, 1 on error
l_int32 pixCopySpp ( PIX *pixd, PIX *pixs )
pixCopySpp() Input: pixd pixs Return: 0 if OK, 1 on error
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 error
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.
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.
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.
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.
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.
l_int32 pixDestroyColormap ( PIX *pix )
pixDestroyColormap() Input: pix Return: 0 if OK, 1 on error
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.
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().
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.
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 error
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);
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 error
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!
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 error
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.
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.
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().
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 error
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 error
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.
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.
l_int32 pixSizesEqual ( PIX *pix1, PIX *pix2 )
pixSizesEqual() Input: two pix Return: 1 if the two pix have same {h, w, d}; 0 otherwise.
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]
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.
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.
Zakariyya Mughal <zmughal@cpan.org>
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.
To install Image::Leptonica, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Image::Leptonica
CPAN shell
perl -MCPAN -e shell install Image::Leptonica
For more information on module installation, please visit the detailed CPAN module installation guide.