public void ShowGlyphAsDirectedContours_Cairo()
{
//load the glyph
Typeface typeFace;
using (var fs = Utility.ReadFile(Utility.FontDir + fontFileName))
{
var reader = new OpenFontReader();
typeFace = reader.Read(fs);
}
Glyph glyph = typeFace.Lookup(character);
Bounds boundingBox = typeFace.Bounds;
short ascender = typeFace.Ascender;
//read polygons and quadratic bezier segments
GlyphLoader.Read(glyph, out var polygons, out var quadraticBezierSegments);
//The actual position of points should apply ascender offset
var offset = new Vector(0, ascender);
// draw to an image
using (Cairo.ImageSurface surface = new Cairo.ImageSurface(Cairo.Format.Argb32,
boundingBox.XMax - boundingBox.XMin,
boundingBox.YMax - boundingBox.YMin))
using (Cairo.Context g = new Cairo.Context(surface))
{
//set surface back ground to white (1,1,1,1)
g.SetSourceColor(CairoEx.ColorWhite);
g.Paint();
//polygons
for (var i = 0; i < polygons.Count; i++)
{
var polygon = polygons[i];
var startPoint = polygon[0] + offset;
g.MoveTo(startPoint.X, startPoint.Y);
var previousPoint = startPoint;
foreach (var point in polygon)
{
var p = point + offset;
g.LineTo(p.X, p.Y);
g.DrawArrow(previousPoint, p);
previousPoint = p;
}
g.LineTo(startPoint.X, startPoint.Y);
g.DrawArrow(previousPoint, startPoint);
}
g.LineWidth = polygonLineWidth;
g.SetSourceColor(polygonColor.ToCairoColor());
g.Stroke();
//quadratic bezier segments
foreach (var segment in quadraticBezierSegments)
{
var p0 = segment.Item1 + offset;
var c = segment.Item2 + offset;
var p1 = segment.Item3 + offset;
g.MoveTo(p0.X, p0.Y);
g.QuadraticTo(c.X, c.Y, p1.X, p1.Y);
}
g.LineWidth = quadraticLineWidth;
g.SetSourceColor(quadraticSegmentColor.ToCairoColor());
g.Stroke();
//start points
g.SetSourceColor(startPointColor.ToCairoColor());
for (var i = 0; i < polygons.Count; i++)
{
var polygon = polygons[i];
var startPoint = polygon[0] + offset;
g.Arc(startPoint.x, startPoint.y, 10, 0, System.Math.PI * 2);
g.Fill();
}
//show the image of contours
var path = $"{OutputDir}{Path.DirectorySeparatorChar}{fontFileName}_{character}.png";
surface.WriteToPng(path);
Util.OpenImage(path);
}
}