iOS & macOS Charting Documentation - SciChart iOS & macOS Charts SDK v4.x

The SCIFreehandDrawingAnnotation

he SCIFreehandDrawingAnnotation allows for freehand drawing directly on the chart surface by capturing a sequence of points that form a continuous brush stroke.

Freehand Drawing Annotation

NOTE: Examples of the Annotations usage can be found in the SciChart iOS Examples Suite as well as on GitHub:

Freehand Drawing Annotation - Obj-C/Swift

A SCIFreehandDrawingAnnotation is a multi-point annotation that stores a collection of points to represent a freehand path drawn by the user.

The SCIFreehandDrawingAnnotation can be configured using the properties and method listed in the table below:

Field	Description
`SCIFreehandDrawingAnnotation.stroke`	Defines the stroke style (color and thickness) of the pen.
`SCIFreehandDrawingAnnotation.drawId`	A unique identifier for the annotation instance.
`SCIFreehandDrawingAnnotation.selectionOffset`	Extra padding applied around the selection bounds.

To learn more about Pens and Brushes and how to utilize them, please refer to the SCIPenStyle, SCIBrushStyle article.

NOTE: To learn more about Annotations in general - please see the Common Annotation Features article.

Adding Points

Points for a SCIFreehandDrawingAnnotation are defined sequentially using the [appendPointWithX:y:] method, which appends each new coordinate to the existing path to form a continuous freehand stroke. The clearPoints method can be used to remove all previously added points, resetting the annotation so that it no longer renders until new points are appended.

NOTE: The xAxisId and yAxisId must be supplied if you have axis with non-default Axis Ids, e.g. in multi-axis scenario.

Create a FreehandDrawingAnnotation

A SCIFreehandDrawingAnnotation can be added onto a chart using the following code:

// Assume a surface has been created and configured somewhere
id surface;

SCIFreehandDrawingAnnotation *freehandDrawing = [SCIFreehandDrawingAnnotation new];

// Append points for the path
[freehandDrawing appendPointWithX:@(224) y:@(11000)];
[freehandDrawing appendPointWithX:@(250) y:@(12000)];
[freehandDrawing appendPointWithX:@(220) y:@(11400)];
[freehandDrawing appendPointWithX:@(224) y:@(11000)];

// Customize appearance
freehandDrawing.stroke = [[SCISolidPenStyle alloc] initWithColorCode:0xFFFF0000 thickness:3];

// Enable interaction
freehandDrawing.isEditable = YES;

// Add to chart surface
[surface.annotations add: freehandDrawing];

// Assume a surface has been created and configured somewhere
let surface: ISCIChartSurface

let freehandDrawing = SCIFreehandDrawingAnnotation()

// Append points for the path
freehandDrawing.appendPointWith(x: NSNumber(value: 224), y: NSNumber(value: 11000))
freehandDrawing.appendPointWith(x: NSNumber(value: 250), y: NSNumber(value: 12000))
freehandDrawing.appendPointWith(x: NSNumber(value: 220), y: NSNumber(value: 11400))
freehandDrawing.appendPointWith(x: NSNumber(value: 224), y: NSNumber(value: 11000))

// Customize appearance
freehandDrawing.stroke = SCISolidPenStyle(color: SCIColor.red, thickness: 3)

// Enable interaction
freehandDrawing.isEditable = true

// Add to chart surface
surface.annotations.add(freehandDrawing)

NOTE: For interactive creation of SCIFreehandDrawingAnnotation, use the corresponding annotation creation modifier SCIFreehandDrawingModifier available in SciChart iOS.

NOTE: To learn more about other Annotation Types, available out of the box in SciChart, please find the comprehensive list in the Annotation APIs article.