KDE 3.5 API Reference kviewshell
GBitmap Class Reference
Bilevel and gray-level images. More...
#include <GBitmap.h>
Public Types | |
| enum | { RUNOVERFLOWVALUE = 0xc0 } |
| enum | { RUNMSBMASK = 0x3f } |
| enum | { RUNLSBMASK = 0xff } |
| enum | { MAXRUNSIZE = 0x3fff } |
Public Member Functions | |
| void | check_border () const |
| void | destroy (void) |
| virtual | ~GBitmap () |
Managing gray levels. | |
| void | binarize_grays (int threshold=0) |
| void | change_grays (int grays) |
| int | get_grays () const |
| void | set_grays (int grays) |
Additive Blit. | |
The blit functions are designed to efficiently construct an anti-aliased image by copying smaller images at predefined locations.
The image of a page, for instance, is composed by copying the images of characters at predefined locations. These functions are fairly optimized. They can directly use compressed GBitmaps (see {compress}). We consider in this section that each GBitmap comes with a coordinate system defined as follows. Position (#0#,#0#) corresponds to the bottom left corner of the bottom left pixel. Position (#1#,#1#) corresponds to the top right corner of the bottom left pixel, which is also the bottom left corner of the second pixel of the second row. Position (w#,h#), where w# and h# denote the size of the GBitmap, corresponds to the top right corner of the top right pixel. | |
| void | blit (const GBitmap *shape, int x, int y, int subsample) |
| void | blit (const GBitmap *bm, int x, int y) |
Accessing the pixels. | |
| unsigned int | columns () const |
| void | minborder (int minimum) |
| unsigned char * | operator[] (int row) |
| const unsigned char * | operator[] (int row) const |
| unsigned int | rows () const |
| unsigned int | rowsize () const |
Optimizing the memory usage. | |
The amount of memory used by bilevel images can be reduced using function {compress}, which encodes the image using a run-length encoding scheme.
The bracket operator decompresses the image on demand. A few highly optimized functions (e.g. {blit}) can use a run-length encoded bitmap without decompressing it. There are unfortunate locking issues associated with this capability (c.f. {share} and {monitor}). | |
| void | compress () |
| unsigned int | get_memory_usage () const |
| GMonitor * | monitor () const |
| void | share () |
| void | uncompress () |
Initialization. | |
| void | fill (unsigned char value) |
| void | init (ByteStream &ref, int border=0) |
| void | init (const GBitmap &ref, const GRect &rect, int border=0) |
| void | init (const GBitmap &ref, int border=0) |
| void | init (int nrows, int ncolumns, int border=0) |
| GBitmap & | operator= (const GBitmap &ref) |
Saving images. | |
The following functions write PBM, PGM and RLE files.
PBM and PGM are well known formats for bilevel and gray-level images. The RLE is a simple run-length encoding scheme for bilevel images. These files can be read using the ByteStream based constructor or initialization function. See {PNM and RLE file formats} for more information. | |
| void | save_pbm (ByteStream &bs, int raw=1) |
| void | save_pgm (ByteStream &bs, int raw=1) |
| void | save_rle (ByteStream &bs) |
Static Public Member Functions | |
Construction. | |
| static GP< GBitmap > | create (ByteStream &ref, const int border=0) |
| static GP< GBitmap > | create (const GBitmap &ref, const GRect &rect, const int border=0) |
| static GP< GBitmap > | create (const GBitmap &ref, const int border) |
| static GP< GBitmap > | create (const GBitmap &ref) |
| static GP< GBitmap > | create (const int nrows, const int ncolumns, const int border=0) |
| static GP< GBitmap > | create (void) |
Public Attributes | |
| GP< ZeroBuffer > | gzerobuffer |
Protected Member Functions | |
| GBitmap (ByteStream &ref, int border=0) | |
| GBitmap (const GBitmap &ref, const GRect &rect, int border=0) | |
| GBitmap (const GBitmap &ref, int border) | |
| GBitmap (const GBitmap &ref) | |
| GBitmap (int nrows, int ncolumns, int border=0) | |
| GBitmap (void) | |
Protected Attributes | |
| unsigned short | border |
| unsigned char * | bytes |
| unsigned char * | bytes_data |
| unsigned short | bytes_per_row |
| GPBuffer< unsigned char > | gbytes_data |
| unsigned short | grays |
| GPBuffer< unsigned char > | grle |
| GPBuffer< unsigned char * > | grlerows |
| unsigned short | ncolumns |
| unsigned short | nrows |
| unsigned char * | rle |
| unsigned int | rlelength |
| unsigned char ** | rlerows |
Stealing or borrowing the memory buffer (advanced). | |
| void | borrow_data (unsigned char &data, int w, int h) |
| void | donate_data (unsigned char *data, int w, int h) |
| void | donate_rle (unsigned char *rledata, unsigned int rledatalen, int w, int h) |
| const unsigned char * | get_rle (unsigned int &rle_length) |
| GP< GBitmap > | rotate (int count=0) |
| unsigned char * | take_data (size_t &offset) |
| static void | append_run (unsigned char *&data, int count) |
| static int | read_run (unsigned char *&data) |
| static int | read_run (const unsigned char *&data) |
Accessing RLE data. | |
| The next functions are useful for processing bilevel images encoded using the run length encoding scheme.
These functions always return zero if the bitmap is not RLE encoded. Function {compress} must be used to ensure that the bitmap is RLE encoded. | |
| int | rle_get_bits (int rowno, unsigned char *bits) const |
| int | rle_get_rect (GRect &rect) const |
| int | rle_get_runs (int rowno, int *rlens) const |
| static void | rle_get_bitmap (const int ncolumns, const unsigned char *&runs, unsigned char *bitmap, const bool invert) |
Detailed Description
Bilevel and gray-level images.Instances of class GBitmap# represent bilevel or gray-level images. Images are usually represented using one byte per pixel. Value zero represents a white pixel. A value equal to the number of gray levels minus one represents a black pixel. The number of gray levels is returned by the function {get_grays} and can be manipulated by the functions {set_grays} and {change_grays}.
The bracket operator returns a pointer to the bytes composing one line of the image. This pointer can be used to read or write the image pixels. Line zero represents the bottom line of the image.
The memory organization is setup in such a way that you can safely read a few pixels located in a small border surrounding all four sides of the image. The width of this border can be modified using the function {minborder}. The border pixels are initialized to zero and therefore represent white pixels. You should never write anything into border pixels because they are shared between images and between lines.
Definition at line 128 of file GBitmap.h.
Member Enumeration Documentation
Constructor & Destructor Documentation
| GBitmap::GBitmap | ( | void | ) | [protected] |
Definition at line 99 of file GBitmap.cpp.
| GBitmap::GBitmap | ( | int | nrows, | |
| int | ncolumns, | |||
| int | border = 0 | |||
| ) | [protected] |
Definition at line 107 of file GBitmap.cpp.
| GBitmap::GBitmap | ( | const GBitmap & | ref | ) | [protected] |
Definition at line 143 of file GBitmap.cpp.
| GBitmap::GBitmap | ( | const GBitmap & | ref, | |
| int | border | |||
| ) | [protected] |
Definition at line 161 of file GBitmap.cpp.
Definition at line 180 of file GBitmap.cpp.
| GBitmap::GBitmap | ( | ByteStream & | ref, | |
| int | border = 0 | |||
| ) | [protected] |
Definition at line 125 of file GBitmap.cpp.
| GBitmap::~GBitmap | ( | ) | [virtual] |
Definition at line 85 of file GBitmap.cpp.
Member Function Documentation
| void GBitmap::append_run | ( | unsigned char *& | data, | |
| int | count | |||
| ) | [inline, static] |
| void GBitmap::binarize_grays | ( | int | threshold = 0 |
) |
Binarizes a gray level image using a threshold.
The number of gray levels is reduced to #2# as in a bilevel image. All pixels whose value was strictly greater than threshold# are set to black. All other pixels are set to white.
Definition at line 512 of file GBitmap.cpp.
| void GBitmap::blit | ( | const GBitmap * | shape, | |
| int | x, | |||
| int | y, | |||
| int | subsample | |||
| ) |
Performs an additive blit of the GBitmap bm# with anti-aliasing.
The GBitmap bm# is first positioned above the current GBitmap in such a way that position (u#,v#) in GBitmap bm# corresponds to position (u#+x#/subsample#,v#+y#/subsample#) in the current GBitmap. This mapping results in a contraction of GBitmap bm# by a factor subsample#. Each pixel of the current GBitmap can be covered by a maximum of subsample^2# pixels of GBitmap bm#. The value of each pixel in GBitmap bm# is then added to the value of the corresponding pixel in the current GBitmap.
{ Example}: Assume for instance that the current GBitmap is initially white (all pixels have value zero). Each pixel of the current GBitmap then contains the sum of the gray levels of the corresponding pixels in GBitmap bm#. There are up to subsample*subsample# such pixels. If for instance GBitmap bm# is a bilevel image (pixels can be #0# or #1#), the pixels of the current GBitmap can take values in range #0# to subsample*subsample#. Note that function blit# does not change the number of gray levels in the current GBitmap. You must call {set_grays} to indicate that there are subsample^2+1# gray levels. Since there is at most 256 gray levels, this also means that subsample# should never be greater than #15#.
{ Remark}: Arguments x# and y# do not represent a position in the coordinate system of the current GBitmap. According to the above discussion, the position is (x/subsample#,y/subsample#). In other words, you can position the blit with a sub-pixel resolution. The resulting anti-aliasing changes are paramount to the image quality.
Definition at line 621 of file GBitmap.cpp.
| void GBitmap::blit | ( | const GBitmap * | bm, | |
| int | x, | |||
| int | y | |||
| ) |
Performs an additive blit of the GBitmap bm#.
The GBitmap bm# is first positioned above the current GBitmap in such a way that position (u#,v#) in GBitmap bm# corresponds to position (u#+x#,v#+y#) in the current GBitmap. The value of each pixel in GBitmap bm# is then added to the value of the corresponding pixel in the current GBitmap.
{ Example}: Assume for instance that the current GBitmap is initially white (all pixels have value zero). This operation copies the pixel values of GBitmap bm# at position (x#,y#) into the current GBitmap. Note that function blit# does not change the number of gray levels in the current GBitmap. You may have to call {set_grays} to specify how the pixel values should be interpreted.
Definition at line 546 of file GBitmap.cpp.
| void GBitmap::borrow_data | ( | unsigned char & | data, | |
| int | w, | |||
| int | h | |||
| ) | [inline] |
Initializes this GBitmap by borrowing a memory segment.
The GBitmap then directly addresses the memory buffer data# provided by the user. This buffer must be large enough to hold w*h# bytes representing each one pixel. The GBitmap object does not ``own'' the buffer: you must explicitly de-allocate the buffer using operator delete []#. This de-allocation should take place after the destruction or the re-initialization of the GBitmap object.
| void GBitmap::change_grays | ( | int | grays | ) |
Changes the number of gray levels.
The argument grays# must be in the range #2# to #256#. All the pixel values are then rescaled and clipped in range #0# to grays-1#.
Definition at line 486 of file GBitmap.cpp.
| void GBitmap::check_border | ( | ) | const |
Definition at line 1629 of file GBitmap.cpp.
| unsigned int GBitmap::columns | ( | ) | const [inline] |
| void GBitmap::compress | ( | ) |
Reduces the memory required for a bilevel image by using a run-length encoded representation.
Functions that need to access the pixel array will decompress the image on demand.
Definition at line 394 of file GBitmap.cpp.
| static GP<GBitmap> GBitmap::create | ( | ByteStream & | ref, | |
| const int | border = 0 | |||
| ) | [inline, static] |
| static GP<GBitmap> GBitmap::create | ( | const int | nrows, | |
| const int | ncolumns, | |||
| const int | border = 0 | |||
| ) | [inline, static] |
| void GBitmap::destroy | ( | void | ) |
| void GBitmap::donate_data | ( | unsigned char * | data, | |
| int | w, | |||
| int | h | |||
| ) |
Same as borrow_data, except GBitmap will call delete[]#.
Definition at line 343 of file GBitmap.cpp.
| void GBitmap::donate_rle | ( | unsigned char * | rledata, | |
| unsigned int | rledatalen, | |||
| int | w, | |||
| int | h | |||
| ) |
Initializes this GBitmap by setting the size to h# rows and w# columns, and directly addressing the memory buffer rledata# provided by the user.
This buffer contains rledatalen# bytes representing the bitmap in run length encoded form. The GBitmap object then ``owns'' the buffer (unlike borrow_data#, but like donate_data#) and will deallocate this buffer when appropriate: you should not deallocate this buffer yourself. The encoding of buffer rledata# is similar to the data segment of the RLE file format (without the header) documented in {PNM and RLE file formats}.
Definition at line 357 of file GBitmap.cpp.
| void GBitmap::fill | ( | unsigned char | value | ) |
| int GBitmap::get_grays | ( | ) | const [inline] |
| unsigned int GBitmap::get_memory_usage | ( | void | ) | const |
| const unsigned char * GBitmap::get_rle | ( | unsigned int & | rle_length | ) |
| void GBitmap::init | ( | ByteStream & | ref, | |
| int | border = 0 | |||
| ) |
Reads PBM, PGM or RLE data from ByteStream ref# into this GBitmap.
The previous content of the GBitmap object is lost. The optional argument border# specifies the size of the optional border of white pixels surrounding the image. See {PNM and RLE file formats} for more information.
Definition at line 291 of file GBitmap.cpp.
Initializes this GBitmap with a rectangular segment rect# of GBitmap ref#.
The optional argument border# specifies the size of the optional border of white pixels surrounding the image.
Definition at line 247 of file GBitmap.cpp.
| void GBitmap::init | ( | const GBitmap & | ref, | |
| int | border = 0 | |||
| ) |
Initializes this GBitmap with the contents of the GBitmap ref#.
The optional argument border# specifies the size of the optional border of white pixels surrounding the image.
Definition at line 227 of file GBitmap.cpp.
| void GBitmap::init | ( | int | nrows, | |
| int | ncolumns, | |||
| int | border = 0 | |||
| ) |
| void GBitmap::minborder | ( | int | minimum | ) |
Makes sure that the border is at least minimum# pixels large.
This function does nothing it the border width is already larger than minimum#. Otherwise it reorganizes the data in order to provide a border of minimum# pixels.
Definition at line 435 of file GBitmap.cpp.
| GMonitor * GBitmap::monitor | ( | ) | const [inline] |
Returns a possibly null pointer to a {GMonitor} for this bitmap.
You should use this monitor to ensure that the data representation of the bitmap will not change while you are using it. We suggest using class {GMonitorLock} which properly handles null monitor pointers.
| unsigned char * GBitmap::operator[] | ( | int | row | ) | [inline] |
| const unsigned char * GBitmap::operator[] | ( | int | row | ) | const [inline] |
| int GBitmap::read_run | ( | unsigned char *& | data | ) | [inline, static] |
| int GBitmap::read_run | ( | const unsigned char *& | data | ) | [inline, static] |
| void GBitmap::rle_get_bitmap | ( | const int | ncolumns, | |
| const unsigned char *& | runs, | |||
| unsigned char * | bitmap, | |||
| const bool | invert | |||
| ) | [static] |
Gets the bitmap line rle data passed.
One line of pixel is stored one with 8 bits per unsigned char# in an array. The array must be large enough to hold the whole line.
Definition at line 1032 of file GBitmap.cpp.
| int GBitmap::rle_get_bits | ( | int | rowno, | |
| unsigned char * | bits | |||
| ) | const |
Gets the pixels for line rowno#.
One line of pixel is stored as unsigned char# values into array bits#. Each pixel is either 1 or 0. The array must be large enough to hold the whole line. The number of pixels is returned.
Definition at line 1083 of file GBitmap.cpp.
| int GBitmap::rle_get_rect | ( | GRect & | rect | ) | const |
Gets the smallest rectangle enclosing black pixels.
Rectangle rect gives the coordinates of the smallest rectangle containing all black pixels. Returns the number of black pixels.
Definition at line 1148 of file GBitmap.cpp.
| int GBitmap::rle_get_runs | ( | int | rowno, | |
| int * | rlens | |||
| ) | const |
Gets the lengths of all runs in line rowno#.
The array rlens# must be large enough to accomodate w+2# integers where w# is the number of columns in the image. These integers represent the lengths of consecutive runs of alternatively white or black pixels. Lengths can be zero in order to allow for lines starting with black pixels. This function returns the total number of runs in the line.
Definition at line 1113 of file GBitmap.cpp.
Rotates bitmap by 90, 180 or 270 degrees anticlockwise and returns a new pixmap, input bitmap is not changed.
count can be 1, 2, or 3 for 90, 180, 270 degree rotation. It returns the same bitmap if not rotated. The input bitmap will be uncompressed for rotation
Definition at line 1557 of file GBitmap.cpp.
| unsigned int GBitmap::rows | ( | ) | const [inline] |
| unsigned int GBitmap::rowsize | ( | ) | const [inline] |
| void GBitmap::save_pbm | ( | ByteStream & | bs, | |
| int | raw = 1 | |||
| ) |
Saves the image into ByteStream bs# using the PBM format.
Argument raw# selects the ``Raw PBM'' (1) or the ``Ascii PBM'' (0) format. The image is saved as a bilevel image. All non zero pixels are considered black pixels. See section {PNM and RLE file formats}.
Definition at line 890 of file GBitmap.cpp.
| void GBitmap::save_pgm | ( | ByteStream & | bs, | |
| int | raw = 1 | |||
| ) |
Saves the image into ByteStream bs# using the PGM format.
Argument raw# selects the ``Raw PGM'' (1) or the ``Ascii PGM'' (0) format. The image is saved as a gray level image. See section {PNM and RLE file formats}.
Definition at line 943 of file GBitmap.cpp.
| void GBitmap::save_rle | ( | ByteStream & | bs | ) |
Saves the image into ByteStream bs# using the RLE file format.
The image is saved as a bilevel image. All non zero pixels are considered black pixels. See section {PNM and RLE file formats}.
Definition at line 985 of file GBitmap.cpp.
| void GBitmap::set_grays | ( | int | grays | ) |
Sets the number of gray levels without changing the pixels.
Argument grays# must be in range #2# to #256#.
Definition at line 474 of file GBitmap.cpp.
| void GBitmap::share | ( | ) |
Associates a {GMonitor} with this bitmap.
This function should be called on all bitmaps susceptible of being simultaneously used by several threads. It will make sure that function {monitor} returns a pointer to a suitable monitor for this bitmap.
Definition at line 461 of file GBitmap.cpp.
| unsigned char * GBitmap::take_data | ( | size_t & | offset | ) |
Steals the memory buffer of a GBitmap.
This function returns the address of the memory buffer allocated by this GBitmap object. The offset of the first pixel in the bottom line is written into variable offset#. Other lines can be accessed using pointer arithmetic (see {rowsize}). The GBitmap object no longer ``owns'' the buffer: you must explicitly de-allocate the buffer using operator delete []#. This de-allocation should take place after the destruction or the re-initialization of the GBitmap object. This function will return a null pointer if the GBitmap object does not ``own'' the buffer in the first place.
Definition at line 372 of file GBitmap.cpp.
| void GBitmap::uncompress | ( | ) |
Decodes run-length encoded bitmaps and recreate the pixel array.
This function is usually called by operator[]# when needed.
Definition at line 413 of file GBitmap.cpp.
Member Data Documentation
unsigned short GBitmap::border [protected] |
unsigned char* GBitmap::bytes [protected] |
unsigned char* GBitmap::bytes_data [protected] |
unsigned short GBitmap::bytes_per_row [protected] |
GPBuffer<unsigned char> GBitmap::gbytes_data [protected] |
unsigned short GBitmap::grays [protected] |
GPBuffer<unsigned char> GBitmap::grle [protected] |
GPBuffer<unsigned char *> GBitmap::grlerows [protected] |
| GP<ZeroBuffer> GBitmap::gzerobuffer |
unsigned short GBitmap::ncolumns [protected] |
unsigned short GBitmap::nrows [protected] |
unsigned char* GBitmap::rle [protected] |
unsigned int GBitmap::rlelength [protected] |
unsigned char** GBitmap::rlerows [protected] |
The documentation for this class was generated from the following files:
