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README
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This repo has been moved to Codeberg and may be out of date on GitHub.
Canonical repo: https://codeberg.org/maandree/libglitter
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 (optionally) apply hinting to the
text so that the glyph outlines aligns with the output's
pixel-grid as closely as possible. The next step is to get
the output's subpixel arrangement and scaling factor, then
assuming that the output's subpixel arrangement is subpixel-
rendering compatible and that its native resolution is used,
you rasterise the text using greyscale-antialiasing into a
raster sized according to the output's horizontal and vertical
subpixel densities (rather than pixel densities as normally
done with greyscale-antialiasing; some subpixels may have be
counted multiple times depending on the subpixel arrangement).
At this point, depending on final result, you may (will
probably) want to use libglitter_redistribute_energy_double(3)
or libglitter_redistribute_energy_float(3) to make the text a
bit blurrier but reduce colour fringing. 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), this is when libglitter is first used in this
process; 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 model, the application can use
libglitter_get_colour_model_conversion_matrix_double(3)
and libglitter_colour_model_convert_rasters_double(3) or
libglitter_get_colour_model_conversion_matrix_float(3)
and libglitter_colour_model_convert_rasters_float(3) to
convert a colour model the application can output in. It is
however out of the scope of libglitter to get the output's
colour model and the conversion matrix to any other colour
model 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)