Appends a cubic Bézier curve to the receiver's path.
For this we'll write a method randomPath - UIBezierPath that returns a random path (a rectangle, a circle or a triangle). The circle is easy to create, we just call the UIBezierPath(ovalInRect) constructor, the triangle is a bit trickier to create, you can find the exact details below. Additionally I filtered out the annoying short lines metioned above and exported the UIBezierPath as SVG file. As far as we can see a radius of 27 pixels at 120×120 pixel icon size produces a pretty good match. Download it here. In case you wonder how I introspected the UIBezierPath to draw the images above – here is the UIView code.
- (void)addCurveToPoint:(CGPoint)endPoint controlPoint1:(CGPoint)controlPoint1 controlPoint2:(CGPoint)controlPoint2
Parameters of [UIBezierPath addCurveToPoint]
endPoint
The end point of the curve.
controlPoint1
The first control point to use when computing the curve.
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controlPoint2The second control point to use when computing the curve.
Discussion of [UIBezierPath addCurveToPoint]
This method appends a cubic Bézier curve from the current point to the end point specified by the endPoint parameter. The two control points define the curvature of the segment. Figure 2 shows an approximation of a cubic Bézier curve given a set of initial points. The exact curvature of the segment involves a complex mathematical relationship between all of the points and is well documented online.
Figure 2 A cubic Bézier curve
You must set the path's current point (using the moveToPoint: method or through the previous creation of a line or curve segment) before you call this method. If the path is empty, this method does nothing. After adding the curve segment, this method updates the current point to the value in point.
UIBezierPath addCurveToPoint example.
void getPointsFromBezier(void *info, const CGPathElement *element)
{
NSMutableArray *bezierPoints = (__bridge NSMutableArray *)info;
// Retrieve the path element type and its points
CGPathElementType type = element->type;
CGPoint *points = element->points;
// Add the points if they're available (per type)
if (type != kCGPathElementCloseSubpath)
{
[bezierPoints addObject:VALUE(0)];
if ((type != kCGPathElementAddLineToPoint) &&
(type != kCGPathElementMoveToPoint))
[bezierPoints addObject:VALUE(1)];
}
if (type kCGPathElementAddCurveToPoint)
[bezierPoints addObject:VALUE(2)];
}
Example of [UIBezierPath addCurveToPoint].
{
#define commonY 117
CGPoint point1 = CGPointMake(20, 20);
CGPoint point2 = CGPointMake(100, commonY);
CGPoint point3 = CGPointMake(200, 50);
CGPoint controlPoint1 = CGPointMake(50, 60);
CGPoint controlPoint2 = CGPointMake(20, commonY);
CGPoint controlPoint3 = CGPointMake(200, commonY);
CGPoint controlPoint4 = CGPointMake(250, 75);
UIBezierPath *path1 = [UIBezierPath bezierPath];
UIBezierPath *path2 = [UIBezierPath bezierPath];
[path1 setLineWidth:3.0];
[path1 moveToPoint:point1];
[path1 addCurveToPoint:point2 controlPoint1:controlPoint1 controlPoint2:controlPoint2];
[[UIColor blueColor] set];
[path1 stroke];
[path2 setLineWidth:3.0];
[path2 moveToPoint:point2];
[path2 addCurveToPoint:point3 controlPoint1:controlPoint3 controlPoint2:controlPoint4];
[[UIColor orangeColor] set];
[path2 stroke];
}
UIBezierPath addCurveToPoint example.
return [[curvePath retain] autorelease];
}
- (void)setCurvePath:(UIBezierPath *)newPath {
id tmp = curvePath;
curvePath = [newPath retain];
[tmp release];
state = BezierStateNone;
[self setNeedsDisplay];
}
- (void)_updateCurve {
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:startPt];
[path addCurveToPoint:endPt controlPoint1:cPt1 controlPoint2:cPt2];
}
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␡- Setting Line Parameters
This chapter is from the book
This chapter is from the book
Setting Line Parameters
Each context stores line width as part of its graphics state. You can adjust that line width by calling CGContextSetLineWidth() and passing the point size as its parameter. Subsequent drawing operations inherit the change in that state. That width does not, however, apply to UIBezierPath instances, the primary drawing tool for UIKit. Every UIKit path permits you to adjust its stroke width by setting its lineWidth parameter. Whatever value this is set to wins out over any context settings.
Take a look at Listing 1-14. It creates a path and sets its line width to 4. Then it instructs the context to use a 20-point-wide line. Figure 1-16 shows the result of these drawing requests. As the image demonstrates, drawing the path through Quartz honors that 20-point width. Drawing through UIKit overrides the context state with the path parameter.
Listing 1-14 Conflicting Line Widths
Figure 1-16 Some Quartz context semantics are implemented orthogonally to UIKit. The smaller interior stroke does not inherit the context's default line width.
UIKit's approach binds line width semantics to the UIBezierPath object and not to the context as a whole. Video editor robot 2 0 download free. That's not a bad thing. Pushing a line width state in order to draw a shape makes less sense than associating that width with a particular object. It is not, however, a consistent thing. This approach is not universal—at least not yet. Copy clip 2 9 9 – clipboard manager salary. You can see this by trying out dashes.
Dashes
Dash patterns do not demonstrate the UIKit/Quartz dichotomy seen with line width. Changes made to the context state will affect UIKit paths, whether you use the UIKit or Quartz entry points. To set a path's dash pattern in UIKit, use the setLineDash:count:phase: method.
This code snippet creates the output shown in Figure 1-17:
Figure 1-17 Dashes can be set in the context state or applied to a path instance.
This snippet uses three arguments. The first sets the dash pattern (6 points on, 2 points off), the second counts the first argument (2 items), and the third specifies a phase offset—that is, how far into the pattern to start. 0 means default to the normal layout pattern. You'll read more about dashes in Chapter 4.
Setting Line Parameters
Each context stores line width as part of its graphics state. You can adjust that line width by calling CGContextSetLineWidth() and passing the point size as its parameter. Subsequent drawing operations inherit the change in that state. That width does not, however, apply to UIBezierPath instances, the primary drawing tool for UIKit. Every UIKit path permits you to adjust its stroke width by setting its lineWidth parameter. Whatever value this is set to wins out over any context settings.
Take a look at Listing 1-14. It creates a path and sets its line width to 4. Then it instructs the context to use a 20-point-wide line. Figure 1-16 shows the result of these drawing requests. As the image demonstrates, drawing the path through Quartz honors that 20-point width. Drawing through UIKit overrides the context state with the path parameter.
Listing 1-14 Conflicting Line Widths
Figure 1-16 Some Quartz context semantics are implemented orthogonally to UIKit. The smaller interior stroke does not inherit the context's default line width.
UIKit's approach binds line width semantics to the UIBezierPath object and not to the context as a whole. Video editor robot 2 0 download free. That's not a bad thing. Pushing a line width state in order to draw a shape makes less sense than associating that width with a particular object. It is not, however, a consistent thing. This approach is not universal—at least not yet. Copy clip 2 9 9 – clipboard manager salary. You can see this by trying out dashes.
Dashes
Dash patterns do not demonstrate the UIKit/Quartz dichotomy seen with line width. Changes made to the context state will affect UIKit paths, whether you use the UIKit or Quartz entry points. To set a path's dash pattern in UIKit, use the setLineDash:count:phase: method.
This code snippet creates the output shown in Figure 1-17:
Figure 1-17 Dashes can be set in the context state or applied to a path instance.
This snippet uses three arguments. The first sets the dash pattern (6 points on, 2 points off), the second counts the first argument (2 items), and the third specifies a phase offset—that is, how far into the pattern to start. 0 means default to the normal layout pattern. You'll read more about dashes in Chapter 4.
The same effect can be applied to the context as a whole by calling the equivalent Quartz function, CGContextSetLineDash(). This next code snippet also produces the output shown in Figure 1-17. It just gets there in a different way: