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NAME
libglitter - Subpixel-rendering library
DESCRIPTION
libglitter is a C library for subpixel-rendered text from
an greyscale-antialiased text image. libglitter is designed
to be used in conjunction with other font libraries: it can
neither rasterise glyphs nor does it know about the montor's
subpixel layout or rendering configurations.
To use libglitter you first need to output's pixel density,
then you apply hinting to the text you want to render using
this information. The next step is to get the output's
subpixel arrangement and scaling factor, then assuming that
the output's subpixel arrangement i subpixel-rendering
compatible and that the native resolution is used, you
multiply the output's DPI:s so that you get the number of
subpixels per inch instead of number of pixels per inch
(some subpixels may have be counted multiple times depending
on the subpixel arrangement) and you create a greyscale
raster of the text for these new DPIs. After this you
create an uninitialised colour raster for text and the
output's pixel density, and split it into one raster per
colour channel using libglitter_split_uint64_raster(3)
or libglitter_split_uint32_raster(3), alternatively you
create one raster for each colour channel directly. Then you
use libglitter_compose_double(3), libglitter_compose_float(3),
libglitter_compose_uint64(3), libglitter_compose_uint32(3),
libglitter_compose_uint16(3), or libglitter_compose_uint8(3)
to create the subpixel-antialiased image of the text; you
may have to first call libglitter_reorder_rasters(3) to
put the rasters in the expected order.
An optional next step is to use lessen the intensity of the
subpixel-antialiasing with libglitter_desaturate_double(3),
libglitter_desaturate_float(3), libglitter_per_channel_-
desaturate_double(3), or libglitter_per_channel_desaturate_-
float(3).
Then, if the application cannot output directly to the
output's colour space, the application can use
libglitter_get_colour_space_conversion_matrix_double(3)
and libglitter_colour_space_convert_rasters_double(3) or
libglitter_get_colour_space_conversion_matrix_float(3)
and libglitter_colour_space_convert_rasters_float(3) to
convert a colour space the application can output in.
It is however out of the scope of libglitter to get the
output's colour space and the conversion matrix to any
other colour space than sRGB or CIE XYZ.
The finally step of the rendering process is out of scope
for libglitter, but is to ensure that all floating-point
values (if floating-point rasters are used) are withing
[0, 1] and convert the rasters, which only contain
ink-on intensities, into the desired colour's with the
output's transfer function applied.
The application may also desire to call libglitter_enable_-
acceleration(3) at the beginning of its execution to enable
any implemented and supported hardware acceleration. This
may however be an expensive process, and may not be
desirable for all applications.
SEE ALSO
libfonts(7)
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