NAME
Image::Leptonica::Func::readfile
VERSION
version 0.04
readfile.c
readfile.c: reads image on file into memory
Top-level functions for reading images from file
PIXA *pixaReadFiles()
PIXA *pixaReadFilesSA()
PIX *pixRead()
PIX *pixReadWithHint()
PIX *pixReadIndexed()
PIX *pixReadStream()
Read header information from file
l_int32 pixReadHeader()
Format finders
l_int32 findFileFormat()
l_int32 findFileFormatStream()
l_int32 findFileFormatBuffer()
l_int32 fileFormatIsTiff()
Read from memory
PIX *pixReadMem()
l_int32 pixReadHeaderMem()
Test function for I/O with different formats
l_int32 ioFormatTest()
Supported file formats:
(1) Reading is supported without any external libraries:
bmp
pnm (including pbm, pgm, etc)
spix (raw serialized)
(2) Reading is supported with installation of external libraries:
png
jpg (standard jfif version)
tiff (including most varieties of compression)
gif
webp
(3) This file format is recognized by the library but reading
is not supported:
jp2 (jpeg2000)
(4) All other file types will get an "unknown format" error.FUNCTIONS
fileFormatIsTiff
l_int32 fileFormatIsTiff ( FILE *fp )
fileFormatIsTiff()
Input: fp (file stream)
Return: 1 if file is tiff; 0 otherwise or on errorfindFileFormat
l_int32 findFileFormat ( const char *filename, l_int32 *pformat )
findFileFormat()
Input: filename
&format (<return>)
Return: 0 if OK, 1 on error or if format is not recognizedfindFileFormatBuffer
l_int32 findFileFormatBuffer ( const l_uint8 *buf, l_int32 *pformat )
findFileFormatBuffer()
Input: byte buffer (at least 12 bytes in size; we can't check)
&format (<return>)
Return: 0 if OK, 1 on error or if format is not recognized
Notes:
(1) This determines the file format from the first 12 bytes in
the compressed data stream, which are stored in memory.
(2) For tiff files, this returns IFF_TIFF. The specific tiff
compression is then determined using findTiffCompression().findFileFormatStream
l_int32 findFileFormatStream ( FILE *fp, l_int32 *pformat )
findFileFormatStream()
Input: fp (file stream)
&format (<return>)
Return: 0 if OK, 1 on error or if format is not recognized
Notes:
(1) Important: Side effect -- this resets fp to BOF.ioFormatTest
l_int32 ioFormatTest ( const char *filename )
ioFormatTest()
Input: filename (input file)
Return: 0 if OK; 1 on error or if the test fails
Notes:
(1) This writes and reads a set of output files losslessly
in different formats to /tmp, and tests that the
result before and after is unchanged.
(2) This should work properly on input images of any depth,
with and without colormaps.
(3) All supported formats are tested for bmp, png, tiff and
non-ascii pnm. Ascii pnm also works (but who'd ever want
to use it?) We allow 2 bpp bmp, although it's not
supported elsewhere. And we don't support reading
16 bpp png, although this can be turned on in pngio.c.
(4) This silently skips png or tiff testing if HAVE_LIBPNG
or HAVE_LIBTIFF are 0, respectively.pixRead
PIX * pixRead ( const char *filename )
pixRead()
Input: filename (with full pathname or in local directory)
Return: pix if OK; null on error
Notes:
(1) See at top of file for supported formats.pixReadHeader
l_int32 pixReadHeader ( const char *filename, l_int32 *pformat, l_int32 *pw, l_int32 *ph, l_int32 *pbps, l_int32 *pspp, l_int32 *piscmap )
pixReadHeader()
Input: filename (with full pathname or in local directory)
&format (<optional return> file format)
&w, &h (<optional returns> width and height)
&bps <optional return> bits/sample
&spp <optional return> samples/pixel (1, 3 or 4)
&iscmap (<optional return> 1 if cmap exists; 0 otherwise)
Return: 0 if OK, 1 on error
Notes:
(1) This reads the actual headers for jpeg, png, tiff and pnm.
For bmp and gif, we cheat and read the entire file into a pix,
from which we extract the "header" information.pixReadHeaderMem
l_int32 pixReadHeaderMem ( const l_uint8 *data, size_t size, l_int32 *pformat, l_int32 *pw, l_int32 *ph, l_int32 *pbps, l_int32 *pspp, l_int32 *piscmap )
pixReadHeaderMem()
Input: data (const; encoded)
datasize (size of data)
&format (<optional returns> image format)
&w, &h (<optional returns> width and height)
&bps <optional return> bits/sample
&spp <optional return> samples/pixel (1, 3 or 4)
&iscmap (<optional return> 1 if cmap exists; 0 otherwise)
Return: 0 if OK, 1 on error
Notes:
(1) This reads the actual headers for jpeg, png, tiff and pnm.
For bmp and gif, we cheat and read all the data into a pix,
from which we extract the "header" information.
(2) On windows, this will only read tiff formatted files from
memory. For other formats, it requires fmemopen(3).
Attempts to read those formats will fail at runtime.
(3) findFileFormatBuffer() requires up to 8 bytes to decide on
the format. That determines the constraint here.pixReadIndexed
PIX * pixReadIndexed ( SARRAY *sa, l_int32 index )
pixReadIndexed()
Input: sarray (of full pathnames)
index (into pathname array)
Return: pix if OK; null if not found
Notes:
(1) This function is useful for selecting image files from a
directory, where the integer @index is embedded into
the file name.
(2) This is typically done by generating the sarray using
getNumberedPathnamesInDirectory(), so that the @index
pathname would have the number @index in it. The size
of the sarray should be the largest number (plus 1) appearing
in the file names, respecting the constraints in the
call to getNumberedPathnamesInDirectory().
(3) Consequently, for some indices into the sarray, there may
be no pathnames in the directory containing that number.
By convention, we place empty C strings ("") in those
locations in the sarray, and it is not an error if such
a string is encountered and no pix is returned.
Therefore, the caller must verify that a pix is returned.
(4) See convertSegmentedPagesToPS() in src/psio1.c for an
example of usage.pixReadMem
PIX * pixReadMem ( const l_uint8 *data, size_t size )
pixReadMem()
Input: data (const; encoded)
datasize (size of data)
Return: pix, or null on error
Notes:
(1) This is a variation of pixReadStream(), where the data is read
from a memory buffer rather than a file.
(2) On windows, this will only read tiff formatted files from
memory. For other formats, it requires fmemopen(3).
Attempts to read those formats will fail at runtime.
(3) findFileFormatBuffer() requires up to 8 bytes to decide on
the format. That determines the constraint here.pixReadStream
PIX * pixReadStream ( FILE *fp, l_int32 hint )
pixReadStream()
Input: fp (file stream)
hint (bitwise OR of L_HINT_* values for jpeg; use 0 for no hint)
Return: pix if OK; null on error
Notes:
(1) The hint only applies to jpeg.pixReadWithHint
PIX * pixReadWithHint ( const char *filename, l_int32 hint )
pixReadWithHint()
Input: filename (with full pathname or in local directory)
hint (bitwise OR of L_HINT_* values for jpeg; use 0 for no hint)
Return: pix if OK; null on error
Notes:
(1) The hint is not binding, but may be used to optimize jpeg decoding.
Use 0 for no hinting.pixaReadFiles
PIXA * pixaReadFiles ( const char *dirname, const char *substr )
pixaReadFiles()
Input: dirname
substr (<optional> substring filter on filenames; can be null)
Return: pixa, or null on error
Notes:
(1) @dirname is the full path for the directory.
(2) @substr is the part of the file name (excluding
the directory) that is to be matched. All matching
filenames are read into the Pixa. If substr is NULL,
all filenames are read into the Pixa.pixaReadFilesSA
PIXA * pixaReadFilesSA ( SARRAY *sa )
pixaReadFilesSA()
Input: sarray (full pathnames for all files)
Return: pixa, 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.