I want to create a perfect semi circle at the bottom of my view and now I'm getting just an arc in the top of a rectangle (see attached picture). This is the code I'm using is the following where circularRect is origin = (x = 128, y = 514), size = (width = 64, height = 54)
CGFloat arcHeight = 60.0;
CGRect arcRect = CGRectMake(circularRect.origin.x, circularRect.origin.y + circularRect.size.height - arcHeight, circularRect.size.width, arcHeight);
CGFloat arcRadius = 60;
CGPoint arcCenter = CGPointMake(arcRect.origin.x + arcRect.size.width/2, arcRect.origin.y + arcRadius);
CGFloat angle = acos(arcRect.size.width / (2*arcRadius));
CGFloat startAngle = 270 * M_PI/180 + angle;
CGFloat endAngle = 90 * M_PI/180 - angle;
CGContextAddArc(context, arcCenter.x, arcCenter.y, arcHeight, startAngle, endAngle, 1);
CGContextClip(context);
CGContextClearRect(context, arcRect);
CGContextSetFillColorWithColor(context, [UIColor greenColor].CGColor);
CGContextFillRect( context, arcRect);
What I'm doing wrong? Thanks!
The radius you're supplying to the arc function is too large. Your rectangle width being 64, you can only fit a circle that has a radius of 32 or less in it.
Related
I'm new to core graphics and I'm struggling with a simple task of putting a sweeping circle inside a square. The outcome I got looks like this:
The circle won't appear at the center of the square, and the size of the circle appears much smaller than I specified.
Below is my drawRect method for drawing the circle. I have put the printed-out variable values while debugging in the comments for your convenience. I also printed out the value passed to initWithFrame: frame=(0 0; 256 256). The frame is the orange square you see in the picture.
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGFloat midX = CGRectGetMidX(self.bounds); // bounds = (0 0; 256 256); midX = 128
CGFloat midY = CGRectGetMidY(self.bounds); // midY = 128
CGFloat radius = midY - 4; // radius = 124
// Outer grey pie
[endColor setFill];
CGContextMoveToPoint(context, midX, midY); // move to center
CGContextAddEllipseInRect(context, CGRectMake(midX - radius, midY - radius, radius * 2, radius * 2)); // adds a circle of radius = square_side_length - 4
CGContextFillPath(context); // fill the circle above with grey
// Show the clock
NSTimeInterval seconds = [[NSDate date] timeIntervalSince1970];
CGFloat mod = fmod(seconds, self.period);
CGFloat percent = mod / self.period;
[fillColor setFill];
CGFloat start = -M_PI_2;
CGFloat end = 2 * M_PI;
CGFloat sweep = end * percent + start;
CGContextMoveToPoint(context, midX, midY);
CGContextAddArc(context, midX, midY, radius, start, sweep, 0); // radius = square_side_length - 24
CGContextFillPath(context);
// Innermost white pie
radius -= 50; // radius = square_side_length - 54
[bgColor setFill]; // white
CGContextMoveToPoint(context, midX, midY);
CGContextAddEllipseInRect(context, CGRectMake(midX - radius, midY - radius, radius * 2, radius * 2));
CGContextFillPath(context);
}
And below is the code that adds the clock to its superview:
clock = [[ProgressClock alloc] initWithFrame:self.clockHolder.bounds // bounds=[0 0; 256 256]
period:[TOTPGenerator defaultPeriod]
bgColor:[UIColor whiteColor]
strokeColor:[UIColor colorWithWhite:0 alpha:0.2]
fillColor:[UIColor blueColor]
endColor:[UIColor grayColor]
shade:NO];
[self.clockHolder addSubview:clock];
Can anyone spot the mistake I made? Thanks in advance.
Thanks a lot to #originaluser2's comment, I have fixed this issue simply by moving the clock presenting logic from viewDidLoad to viewDidAppear and the clock showed up perfectly. There was nothing wrong with the drawing code I posted; however the auto-layout initialization and the animation of my clock happened in a sequence that gave my drawing canvas a wrong frame. By putting the drawing logic in viewDidAppear, we are guaranteed that all the auto-layout setup has been completed, thus frames are fixed, before continue onto drawing the circle.
Our designer has asked me to recreate this:
Im subclassing UIView, and I've overridden the drawRect command like this:
[super drawRect:frame];
CGFloat x = self.frame.origin.x;
CGFloat y = self.frame.origin.y;
CGFloat w = self.frame.size.width;
CGFloat h = self.frame.size.height;
CGFloat lineWidth = lineWidthRequested;
CGPoint centerPoint = CGPointMake(w/2, h/2);
CGFloat radius = radiusRequested;
CGFloat startAngle = 3 * M_PI / 2;
CGFloat endAngle = startAngle + percentage * 2 * M_PI;
CGMutablePathRef arc = CGPathCreateMutable();
CGPathAddArc(arc, NULL,
centerPoint.x, centerPoint.y,
radius,
startAngle,
endAngle,
NO);
CGPathRef strokedArc = CGPathCreateCopyByStrokingPath(arc, NULL,
lineWidth,
kCGLineCapButt,
kCGLineJoinMiter, // the default
10); // 10 is default miter limit
CGContextRef c = UIGraphicsGetCurrentContext();
CGContextAddPath(c, strokedArc);
CGContextSetFillColorWithColor(c, [UIColor colorWithRed:239/255.0 green:101/255.0 blue:47/255.0 alpha:1.0].CGColor);
CGContextDrawPath(c, kCGPathFill);
What I ended up with is this:
Gotta still draw the arrowhead. Gonna be easy, right?
After struggling to remember my trig, I found rotation of points around a center on this page:
Rotating a point around an origin in VB
But when I tried translation to objective C to draw the arrowhead, I'm getting very odd results. Here's the code further down in drawRect:
CGFloat triangle[3][2] = {{centerPoint.x + 10, h - (centerPoint.y + radius)},
{centerPoint.x, h - (centerPoint.y + radius + lineWidth/2)},
{centerPoint.x, h - (centerPoint.y + radius - lineWidth/2)}};
for (int idx=0;idx < 3; idx++) {
// translate to origin
triangle[idx][0] -= centerPoint.x;
triangle[idx][1] -= centerPoint.y;
}
CGFloat angDistance = endAngle - startAngle;
CGFloat ct = cos(angDistance);
CGFloat st = sin(angDistance);
for (int idx=0;idx < 3; idx++) {
// rotate
triangle[idx][0] = ct * triangle[idx][0] - st * triangle[idx][1];
triangle[idx][1] = -st * triangle[idx][0] + ct * triangle[idx][1];
}
for (int idx=0;idx < 3; idx++) {
// translate back to position
triangle[idx][0] += centerPoint.x;
triangle[idx][1] += centerPoint.y;
}
NSLog(#"Rotating through %g, %06.1f,%06.1f , ct - %g, st - %g",angDistance, triangle[0][0],triangle[0][1],ct, st);
// XXX todo draw the filled triangle at end.
// draw a red triangle, the point of the arrow
CGContextSetFillColorWithColor(c, [[UIColor greenColor] CGColor]);
CGContextMoveToPoint(c, triangle[0][0], triangle[0][1]);
CGContextAddLineToPoint(c, triangle[1][0], triangle[1][1]);
CGContextAddLineToPoint(c, triangle[2][0], triangle[2][1]);
CGContextFillPath(c);
I was expecting that I make these points, then translate them to an origin, rotate, and then translate them back, I'd be laughing.
However, that's not what's happening...as the percentage increases from 0 to 2pi, the arrowhead draws itself in a vaguely triangular route. When the angDistance is zero or pi, the arrowhead is in the right place. As I head towards pi/2 or 3pi/2 though, the arrowhead heads off towards the lower corners of an enclosing rect.
I must be doing something blatantly stupid, but I can't for the life of me see it.
Any ideas?
Thanks,
-Ken
I'd suggest constructing a path for the entire outline of the desired shape and then "fill" that path with the desired color. That eliminates any risk of any gaps or anything not quite lining up.
Thus, this path might consisting of an arc for the outside of the arrow, two lines for the head of the arrow, an arc back for the inside of the arrow, and then close the path. That might look like:
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, self.arrowColor.CGColor);
CGPoint center = CGPointMake(rect.size.width / 2.0, rect.size.height / 2.0);
CGContextMoveToPoint(context, center.x + cosf(self.startAngle) * (self.radius + self.lineWidth / 2.0),
center.y + sinf(self.startAngle) * (self.radius + self.lineWidth / 2.0));
CGContextAddArc(context, center.x, center.y, self.radius + self.lineWidth / 2.0, self.startAngle, self.endAngle, !self.clockwise);
CGFloat theta = asinf(self.lineWidth / self.radius / 2.0) * (self.clockwise ? 1.0 : -1.0);
CGFloat pointDistance = self.radius / cosf(theta);
CGContextAddLineToPoint(context, center.x + cosf(self.endAngle + theta) * pointDistance,
center.y + sinf(self.endAngle + theta) * pointDistance);
CGContextAddLineToPoint(context, center.x + cosf(self.endAngle) * (self.radius - self.lineWidth / 2.0),
center.y + sinf(self.endAngle) * (self.radius - self.lineWidth / 2.0));
CGContextAddArc(context, center.x, center.y, self.radius - self.lineWidth / 2.0, self.endAngle, self.startAngle, self.clockwise);
CGContextClosePath(context);
CGContextDrawPath(context, kCGPathFill);
}
The only trick here was coming up with the right point for the end of the arrow. I've improved the choice to handle fatter arrows a little better, but you should feel free to use whatever you feel is best for your application.
Thus, the following code:
self.arrowView.radius = 100;
self.arrowView.arrowColor = [UIColor blueColor];
self.arrowView.lineWidth = 40;
self.arrowView.startAngle = -M_PI_2;
self.arrowView.endAngle = M_PI;
self.arrowView.clockwise = TRUE;
would yield the following (which I'm animating with a CADisplayLink):
This uses the start angle of zero as meaning the "3 o'clock" position, but you can obviously tweak this as you see fit. But hopefully it illustrates one approach to the problem.
By the way, while I've answered the question of how to do this with CoreGraphics, I wouldn't necessarily suggest doing so. For example, in https://github.com/robertmryan/CircularArrowDemo, I don't implement drawRect, but instead update a CAShapeLayer. By doing this, not only do I avoid drawRect inefficiencies, but one could theoretically also change how you use this CAShapeLayer (e.g. use it as a mask for some UIView, revealing some more interesting color gradation (or other image) behind it).
Here is another solution (not very scalable though). This solution assumes this is like a logo where the angle/percent of circle drawn will not change.
- (void)drawRect:(CGRect)rect {
UIBezierPath *circleOutline = [UIBezierPath bezierPath];
[self.circleColor setStroke];
[circleOutline setLineWidth:self.bounds.size.width*0.15];
[circleOutline addArcWithCenter:CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2) radius:self.bounds.size.width/2-circleOutline.lineWidth/2 startAngle:3*M_PI/2 endAngle:3*M_PI/4 clockwise:YES];
[circleOutline stroke];
[self addArrowView:circleOutline];
}
- (void)addArrowView:(UIBezierPath *)path {
for (int x = 0; x < self.bounds.size.width/2; x++) {
for (int y = self.bounds.size.height/2; y < self.bounds.size.height; y++) {
if ([path containsPoint:CGPointMake(x, y)]) {
// Pythagorean Theorem - We want the diagonal length of the square to be lineWidth, so we need to calculate what size
// to make each side of the square to make the diagonal equal to lineWidth
double sideLength = sqrt((path.lineWidth*path.lineWidth)/2);
UIView *arrowView = [[UIView alloc] initWithFrame:CGRectMake(x-sideLength/2, y-sideLength/2, sideLength, sideLength)];
arrowView.backgroundColor = self.circleColor;
[self addSubview:arrowView];
return;
}
}
}
}
would yield:
I'm trying to create an animated pie chart in iOS that acts basically like this:
In a nutshell, it starts as a grey circle, and as the animation progresses the arrow moves around the circle until it gets to the percentage I specify.
I've used the sample code that Zachary Waldowski posted in this SO question:
Animated CAShapeLayer Pie
That's gotten me to the point where I can create the basic animation. The maroon pie piece grows to hit the correct size. What I'm struggling with is how to map the arrow to the animation so that it gets dragged along as the pie piece grows.
Any thoughts on how I can accomplish this?
Okay, I've found the solution.
Building on the work Zachary Waldowski created (see my original post), I was able to do the entire thing in a CALayer.
In a nutshell, I draw one outer circle in maroon, a smaller circle in light gray, a stroked path in white, then draw the triangle for the tip of the arrow by hand.
Here's the relevant section of code that does the magic:
- (void)drawInContext:(CGContextRef)context {
CGRect circleRect = CGRectInset(self.bounds, 1, 1);
CGFloat startAngle = -M_PI / 2;
CGFloat endAngle = self.progress * 2 * M_PI + startAngle;
CGColorRef outerPieColor = [[UIColor colorWithRed: 137.0 / 255.0 green: 12.0 / 255.0 blue: 88.0 / 255.0 alpha: 1.0] CGColor];
CGColorRef innerPieColor = [[UIColor colorWithRed: 235.0 / 255.0 green: 214.0 / 255.0 blue: 227.0 / 255.0 alpha: 1.0] CGColor];
CGColorRef arrowColor = [[UIColor whiteColor] CGColor];
// Draw outer pie
CGFloat outerRadius = CGRectGetMidX(circleRect);
CGPoint center = CGPointMake(CGRectGetMidX(circleRect), CGRectGetMidY(circleRect));
CGContextSetFillColorWithColor(context, outerPieColor);
CGContextMoveToPoint(context, center.x, center.y);
CGContextAddArc(context, center.x, center.y, outerRadius, startAngle, endAngle, 0);
CGContextClosePath(context);
CGContextFillPath(context);
// Draw inner pie
CGFloat innerRadius = CGRectGetMidX(circleRect) * 0.45;
CGContextSetFillColorWithColor(context, innerPieColor);
CGContextMoveToPoint(context, center.x, center.y);
CGContextAddArc(context, center.x, center.y, innerRadius, startAngle, endAngle, 0);
CGContextClosePath(context);
CGContextFillPath(context);
// Draw the White Line
CGFloat lineRadius = CGRectGetMidX(circleRect) * 0.72;
CGFloat arrowWidth = 0.35;
CGContextSetStrokeColorWithColor(context, arrowColor);
CGContextSetFillColorWithColor(context, arrowColor);
CGMutablePathRef path = CGPathCreateMutable();
CGContextSetLineWidth(context, 16);
CGFloat lineEndAngle = ((endAngle - startAngle) >= arrowWidth) ? endAngle - arrowWidth : endAngle;
CGPathAddArc(path, NULL, center.x, center.y, lineRadius, startAngle, lineEndAngle, 0);
CGContextAddPath(context, path);
CGContextStrokePath(context);
// Draw the Triangle pointer
CGFloat arrowStartAngle = lineEndAngle - 0.01;
CGFloat arrowOuterRadius = CGRectGetMidX(circleRect) * 0.90;
CGFloat arrowInnerRadius = CGRectGetMidX(circleRect) * 0.54;
CGFloat arrowX = center.x + (arrowOuterRadius * cosf(arrowStartAngle));
CGFloat arrowY = center.y + (arrowOuterRadius * sinf(arrowStartAngle));
CGContextMoveToPoint (context, arrowX, arrowY); // top corner
arrowX = center.x + (arrowInnerRadius * cosf(arrowStartAngle));
arrowY = center.y + (arrowInnerRadius * sinf(arrowStartAngle));
CGContextAddLineToPoint(context, arrowX, arrowY); // bottom corner
arrowX = center.x + (lineRadius * cosf(endAngle));
arrowY = center.y + (lineRadius * sinf(endAngle));
CGContextAddLineToPoint(context, arrowX, arrowY); // point
CGContextClosePath(context);
CGContextFillPath(context);
[super drawInContext: context];
}
Have the pie with the arrow as an image.
In every step, draw this image, rotating it a little. Draw the gray pie over the image, choosing correct angles for the image rotation.
I believe for some could be very simple to answer and help me.
I have a circle defined in drawRect and wrote a code to define arc of the circle.
CGFloat width = rect.size.width-rect.origin.x;
CGFloat height = rect.size.height-rect.origin.y;
CGFloat xPos = rect.origin.x;
CGFloat yPos = rect.origin.y;
CGFloat arcStake = (width * 2) * 0.25;
CGFloat radius = height/2;
CGPoint centre = CGPointMake(xPos+width/2, yPos+height/2);
CGFloat angle = acos(arcStake/(2*radius));
CGFloat startAng = radians(180) + angle;
CGFloat endAng = radians(360) - angle;
// Define 2 CGPoints of arc
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddArc(path, NULL, centre.x, centre.y, radius, startAng, endAng, 0);
CGPathAddLineToPoint(path, NULL, xPos+width/2, yPos+height/2);
CGPathCloseSubpath(path);
What I want is to define 2 CGPoints of arc.
Here is the image to make it clearer.
A point on a circle with radius r at angle a (where a is measured from the rightmost point of the circle has the following coordinates:
x = r*cos(a) + center.x
y = r*sin(a) + center.y
Is there a way to let users draw a triangle using a circle (transparent circle) in iOS. I was thinking setting three equal points in the circle to create the triangle and as it stretch the circle the triangle gets build. Maybe using bezierPathWithArcCenter or bezierPathWithOvalInRect. Anyone ever done this?
Assuming you've already got gesture recognizers or some other system in place for capturing the location of the user's touches, doing the drawing itself is straightforward.
CGContextRef context = UIGraphicsGetCurrentContext();
// Draw circle
CGFloat derivedRadius = self.radius * self.scale;
CGPoint origin = CGPointMake(self.center.x - derivedRadius, self.center.y - derivedRadius);
CGContextAddEllipseInRect(context, CGRectMake(origin.x, origin.y, derivedRadius * 2, derivedRadius * 2));
// Draw triangle
CGFloat t1 = self.rotation;
CGFloat t2 = self.rotation + ((2 * M_PI) / 3);
CGFloat t3 = self.rotation + ((4 * M_PI) / 3);
CGPoint p1 = CGPointMake(self.center.x + cosf(t1) * derivedRadius, self.center.y + sinf(t1) * derivedRadius);
CGPoint p2 = CGPointMake(self.center.x + cosf(t2) * derivedRadius, self.center.y + sinf(t2) * derivedRadius);
CGPoint p3 = CGPointMake(self.center.x + cosf(t3) * derivedRadius, self.center.y + sinf(t3) * derivedRadius);
CGPoint endpoints[] = { p1, p2, p3, p1 };
CGContextAddLines(context, endpoints, 4);
CGContextStrokePath(context);
Where self.radius, self.scale, self.center, and self.rotation are properties that capture the result of the user's gestures. Rotation should be in radians.