.TH LIBPARSEPCF_GET_BITMAPS 3 LIBPARSEPCF
.SH NAME
libparsepcf_get_bitmaps \- Get glyph bitmaps
.SH SYNOPSIS
.nf
#include <libparsepcf.h>
#define LIBPARSEPCF_BITMAPS /* value omitted */
struct libparsepcf_bitmaps {
size_t \fIglyph_count\fP;
size_t \fIbit_packing\fP;
size_t \fIrow_padding\fP;
int \fImsbyte_first\fP;
int \fImsbit_first\fP;
const uint8_t *\fIbitmap_data\fP;
/* fields intended for internal use omitted */
};
int libparsepcf_get_bitmaps(const void *\fIdata\fP, size_t \fIsize\fP,
const struct libparsepcf_table *\fItable\fP,
struct libparsepcf_bitmaps *\fImeta_out\fP);
int libparsepcf_get_bitmap_offsets(const void *\fIdata\fP, size_t \fIsize\fP,
const struct libparsepcf_table *\fItable\fP,
const struct libparsepcf_bitmaps *\fImeta\fP,
size_t *\fIoffsets_out\fP,
size_t \fIfirst\fP, size_t \fIcount\fP);
.fi
.PP
Link with
.IR -lparsepcf .
.SH DESCRIPTION
Glyphs in PCF fonts are encoded as bitmaps which
can be looked up in the table with the type
.BR LIBPARSEPCF_BITMAPS ,
which can be retrieved with the
.BR libparsepcf_get_tables (3)
function.
.PP
Once the
.B LIBPARSEPCF_BITMAPS
table has been identified, it can be passed as
the third argument
.RI ( table )
to the
.BR libparsepcf_get_bitmaps ()
function along with the font file contents in the
.I data
argument and size, in bytes, of the file in the
.I size
argument. The
.BR libparsepcf_get_bitmaps ()
function will store the number of available
glyphs in
.IR meta_out->glyph_count ,
which shall be used to check that all glyphs
have a bitmap recorded. The
.BR libparsepcf_get_bitmaps ()
function will store information needed to decode
the bitmap in
.IR *meta_out .
.PP
Then the
.BR libparsepcf_get_bitmap_offsets ()
function can be used to get offset from
.I meta_out->bitmap_data
where the bitmap for each glyph is stored.
The first four arguments shall be the
same as with
.BR libparsepcf_get_bitmaps ().
.I first
shall be the index of the glyph with the lowest index
of the glyph the function shall get the bitmap offset
for, and
.I count
shall be the number of consecutive glyphs
(including the first glyph) to get this information
for. For each queried glyph with index
.IR i ,
the bitmap offset will be stored in
.IR offsets_out[i-first] .
.PP
The application shall ensure that
.IR "first + count <= meta->glyph_count" .
.PP
Note that glyph indices are not the same as character
codepoints. See
.BR libparsepcf_get_encoding (3)
for details about mapping characters to glyphs.
.PP
The be able to interpret a glyph's bitmap, it's ink
metrics must also be acquired. The
.BR libparsepcf_get_metrics (3)
function is used to get a glyph's ink metrics. The
ink metrics describe the boundaries of the bitmap,
but the
.BR libparsepcf_get_bitmaps ()
function returns encoding information. The bitmap
encodes the glyph row by row, from top to bottom,
at the end of each row, padding is inserted into
the bitmap to align the beginning of the next row
in the bitmap. It is always padded to a number of
two bytes, specified in
.IR meta_out->row_padding .
For each row, the cells are encoded from left to
right, there are three fields in
.I meta_out
that affect the order of the bits. For example,
the bits can be group in bytes, dual-byte words or
quad-byte words. The number of bytes in each group
is specified in
.IR meta_out->bit_packing ,
which is always a power of two and no greater than
.IR meta_out->row_padding ,
and each these units are intepreted as unsigned integers,
that are either encoded in big endian (most significant
byte first) or little endian (least significant
byte first).
.I meta_out->msbyte_first
will either be 0 or 1. If 0, these units are encoded
in little endian; if 1 these units are encoded in
big endian. Once a unit as been interpreted as in
unsigned integer, its bits can be inspected to
determine the value of each cell the unit covers,
the cells are order from left to right, but the
bits either ordered from least significant to most
significant or from most significant to least
significant, and for each set bit the corresponding
cell is inked and for each cleared bit the
corresponding cell is uninked.
.I meta_out->msbit_first
is used to determine the bit order; it will either
be 0 or 1. If 0, the bits are ordered from least
significant to most significant; if 1, the bits are
ordered from most significant to least significant.
.SH RETURN VALUE
The
.BR libparsepcf_get_bitmaps ()
and
.BR libparsepcf_get_bitmap_offsets ()
functions return 0 upon successful completion.
On failure, -1 is returned and
.I errno
is set appropriately to indicate the error.
.SH ERRORS
The
.BR libparsepcf_get_bitmaps ()
and
.BR libparsepcf_get_bitmap_offsets ()
functions fail if:
.TP
.B EBFONT
The font file is corrupt or unsupported.
.SH SEE ALSO
.BR libparsepcf (7),
.BR libparsepcf_preparse_font (3)
