Path.GetContour Method (Bitmap, Channel, Single)

Syntax

public static Path GetContour(
	Bitmap bitmap,
	Channel channel,
	float level
)

Remarks

The contour has sub-pixel accuracy. Its points are interpolated between pixel centers, so anti-aliased edges and soft masks give smooth lines. GetAlphaContour() follows pixel edges, so its contour has steps.

The pixel (x, y) covers the area from x to x + 1 and from y to y + 1. Pixels outside the bitmap count as 0, so a region that touches the border is closed just outside the bitmap.

You can trace any channel of any pixel format except the spot ones. Alpha of a bitmap without an alpha channel is 1 everywhere. An indexed bitmap is traced in the colors and alpha of its palette.

All subpaths have consistent directions, so you can fill the contour with either filling rule.

The contours of this method and of GetAlphaContour() are offset by half a pixel from each other. Do not mix the contours of the two methods.

Examples

// Trace the alpha channel at 50% with sub-pixel accuracy.
var contour = Path.GetContour(image, Channel.Alpha, 0.5f);

The contours that GetAlphaContour and GetContour return for a small image of a circle, scaled four times.

Exceptions

See Also

Reference

• Path Class
• GetContour Overload
• Aurigma.GraphicsMill.Drawing Namespace

Manual

• Working with Paths