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authorMattias Andrée <maandree@kth.se>2023-01-23 21:38:27 +0100
committerMattias Andrée <maandree@kth.se>2023-01-23 21:38:27 +0100
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parentAdd some tests (diff)
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Add README
Signed-off-by: Mattias Andrée <maandree@kth.se>
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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)