README: add usage information

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 12 insertions, 2 deletions

diff --git a/README b/README
index 82ceaf9..f9fe974 100644
--- a/README
+++ b/README
@@ -12,10 +12,20 @@ DESCRIPTION
 	is what is requied to draw vectorised bitmap fonts and TrueType fonts, but also
 	cubic Bézier curves as this is required for OpenType fonts and elliptical arcs
 	(elliptical rather than circular because it may be need required to strech the
-	circle to support outputs with different vertical and horizontal dot density and
-	to support subpixel antialiasing) as this is commonly used for corners when
+	circle to support outputs with different vertical and horizontal dot density
+	and to support subpixel antialiasing) as this is commonly used for corners when
 	stroking the outline of a glyph.
 
+	The create an image, first create a buffer using rtgrpblib_create_raster(3)
+	(if you already have one that is large enough, you can reinitialise it with
+	rtgrpblib_reset_raster(3)), and than using the drawing functions
+	(rtgrpblib_draw_linear_bezier(3), rtgrpblib_draw_quadratic_bezier(3),
+	rtgrpblib_draw_cubic_bezier(3), and rtgrpblib_draw_elliptical_arc(3)) to
+	draw the components of each shape's outline. When done, create an image
+	using the rtgrpblib_fill_shapes(3) function: you will receive a ink-level
+	map, where the value 0 means background, and 1 means foreground, and values
+	between are colours between (no transfer function is applied).
+
 NOTES
 	Rifunktionsteckensnittsglyfrasteriseringsprogrambiblioteket (hyphenation:
 	ri|funk¦tions-tec¦ken|snit¦ts-glyf-ras¦ter¦iser¦ings-prog¦ram|bib¦lio¦te¦ket)