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authorMattias Andrée <maandree@kth.se>2023-01-23 23:02:20 +0100
committerMattias Andrée <maandree@kth.se>2023-01-23 23:02:20 +0100
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Signed-off-by: Mattias Andrée <maandree@kth.se>
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@@ -2,34 +2,35 @@ 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.
+ 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
+ To use libglitter you first 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 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),
+ 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).
+ 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.
+ 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),
@@ -43,17 +44,17 @@ DESCRIPTION
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.
+ 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 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