I've been using the code below to draw on an UIView
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1.0);
CGContextSetAlpha(context, 0.5);
CGContextSetLineWidth(context, 10.0);
CGContextMoveToPoint(context, point.x, point.y);
CGContextAddLineToPoint(context, point.x, point.y);
CGContextStrokePath(context);
So that part works.
Now how do I clear my drawing? Most of the example just shows the drawing. Having a hardtime finding keyword to google.
Thanks,
Tee
Have you tried CGContextClearRect?
[self setNeedsDisplay];
it sends the message drawRect: to the view.
Related
I am drawing a shape like following :
- (void)drawRect:(CGRect)rect
{
// Draw a cross rectagle
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextMoveToPoint(context, 190, 0);
CGContextAddLineToPoint(context, 220, 0);
CGContextAddLineToPoint(context, 310, 90);
CGContextAddLineToPoint(context, 310, 120);
CGContextSetFillColorWithColor(context, [UIColor lightGrayColor].CGColor);
CGContextFillPath(context);
CGContextRestoreGState(context);
}
I am getting a light-dark cross flag below
Now I would like to draw a stroke around the cross flag I have just drawn
What should I do to achieve this. Please advice me on this issue.
Thanks.
Surely CGContextDrawPath(context, kCGPathFillStroke); is what you're after
You can adjust the pattern and color using:
CGContextSetStrokePattern
CGContextSetStrokeColor
https://developer.apple.com/library/ios/#documentation/graphicsimaging/reference/CGContext/Reference/reference.html
So, in your case, assuming you want a plain black stroke, you'd have:
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextSetLineWidth(context, 2.0);
CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
CGContextSetFillColorWithColor(context, [UIColor lightGrayColor].CGColor);
CGContextMoveToPoint(context, 190, 0);
CGContextAddLineToPoint(context, 220, 0);
CGContextAddLineToPoint(context, 310, 90);
CGContextAddLineToPoint(context, 310, 120);
CGContextClosePath(context);
CGContextDrawPath(context, kCGPathFillStroke);
CGContextFillPath(context);
CGContextRestoreGState(context);
}
Produces:
- (void)drawRect:(CGRect)rect
{
// Draw a cross rectagle
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
//New
CGContextSetLineWidth(context, 2.0);
CGContextMoveToPoint(context, 190, 0);
CGContextAddLineToPoint(context, 220, 0);
CGContextAddLineToPoint(context, 310, 90);
CGContextAddLineToPoint(context, 310, 120);
//New
CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
CGContextSetFillColorWithColor(context, [UIColor lightGrayColor].CGColor);
CGContextFillPath(context);
//New
CGContextStrokePath(context);
CGContextRestoreGState(context);
}
#WDUK :after spending hours to figure it out, I know why your above answer is not working.
The reason is when you do CGContextFillPath first, the path is eventually cleared and then you can no long do CGContextStrokePath on it again.
Therefore in order to do CGContextFillPath and CGContextStrokePath, we have to do
CGContextDrawPath(context, kCGPathFillStroke);
After trying it , I am getting the following
I have UITableView with static cells in 4 sections done in Storyboard. However, I want to change the separator color for one section ([UIColor clearColor]). How can I do that??? Is it actually possible?
I can set the separatorColor to clearColor for the entire table, but not only for one specific section.
Screenshot of table view section:
AFAIK there is no method for this. But you can put a background image to the cell which has a separator at the bottom and set separatorstyle to UITableViewCellSeparatorStyleNone. So you have your own separator in every cell.
Maybe you can achieve your goal by setting the header text for the section to an empty string.
One approach would to create your own UIView subclass and do your own custom drawing in drawRect:. You would take this view and add it as the backgroundView of your table view cell. Something like this:
- (void)drawRect:(CGRect)rect
{
[super drawRect:rect];
// Drawing code
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 1.0);
// Draw black line
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGFloat components[] = {0.0, 0.0, 0.0, 0.3};
CGColorRef blackColor = CGColorCreate(colorspace, components);
CGContextSetStrokeColorWithColor(context, blackColor);
CGContextMoveToPoint(context, 0, rect.size.height - 1.5);
CGContextAddLineToPoint(context, rect.size.width, rect.size.height - 1.5);
CGContextStrokePath(context);
CGColorRelease(blackColor);
// Draw white bottom line
CGFloat whiteComponents[] = {1.0, 1.0, 1.0, 0.75f};
CGColorRef whiteColor = CGColorCreate(colorspace, whiteComponents);
CGContextSetStrokeColorWithColor(context, whiteColor);
CGContextMoveToPoint(context, 0, rect.size.height - 0.5);
CGContextAddLineToPoint(context, rect.size.width, rect.size.height - 0.5);
CGContextStrokePath(context);
CGColorRelease(whiteColor);
// Draw top white line
CGFloat whiteTransparentComponents[] = {1.0, 1.0, 1.0, 0.45};
CGColorRef whiteTransparentColor = CGColorCreate(colorspace, whiteTransparentComponents);
CGContextSetStrokeColorWithColor(context, whiteTransparentColor);
CGContextMoveToPoint(context, 0, 0.5);
CGContextAddLineToPoint(context, rect.size.width, 0.5);
CGContextStrokePath(context);
CGColorRelease(whiteTransparentColor);
CGColorSpaceRelease(colorspace);
}
I am creating a drawing application like this, but I have one issue. The problem is that when I draw a line with one color and then draw a line with another color, it gives me combination of both colors where the lines intersect.
- (void)drawRect:(CGRect)rect
{
[curImage drawAtPoint:CGPointMake(0, 0)];
CGPoint mid1 = midPoint(previousPoint1, previousPoint2);
CGPoint mid2 = midPoint(currentPoint, previousPoint1);
CGContextRef context = UIGraphicsGetCurrentContext();
[self.layer renderInContext:context];
CGContextMoveToPoint(context, mid1.x, mid1.y);
CGContextAddQuadCurveToPoint(context, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y);
CGContextSetLineCap(context, kCGLineCapRound);
CGContextSetLineWidth(context, self.lineWidth);
CGContextSetStrokeColorWithColor(context, self.lineColor.CGColor);
CGContextStrokePath(context);
[super drawRect:rect];
[curImage release];
}
The rest of the project is available on GitHub.
Maybe have a look at blend modes.
https://developer.apple.com/library/mac/#documentation/graphicsimaging/Reference/CGContext/Reference/reference.html#//apple_ref/c/tdef/CGBlendMode
I can draw a line by placing the following into a UIView and connecting it to a storyboard View.
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 5.0);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGFloat components[] = {0.0, 0.0, 1.0, 1.0};
CGColorRef color = CGColorCreate(colorspace, components);
CGContextSetStrokeColorWithColor(context, color);
CGContextMoveToPoint(context, 0, 0);
CGContextAddLineToPoint(context, 10, 50);
CGContextStrokePath(context);
CGColorSpaceRelease(colorspace);
CGColorRelease(color);
}
However, what I want to do is to draw a line whenever a button is pressed. To do this I assume I need to write some code into an IBAction. My problem is that I cannot simply place the above code into the IBAction as it gives me an error.
- (IBAction)draw:(id)sender{
//Place code here
}
My question is, how can I draw a line each time the button is pressed?
How do I connect similar code to draw a different line that will be triggered when I press a button
To draw on a UIView you have to subclass your UIView
In .h
#MyCustomView : UIView {
}
#end
in .m
#implementation MyCustomView
- (void) drawRect: (CGRect) rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 5.0);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGFloat components[] = {0.0, 0.0, 1.0, 1.0};
CGColorRef color = CGColorCreate(colorspace, components);
CGContextSetStrokeColorWithColor(context, color);
CGContextMoveToPoint(context, 0, 0);
CGContextAddLineToPoint(context, 10, 50);
CGContextStrokePath(context);
CGColorSpaceRelease(colorspace);
CGColorRelease(color);
}
In your ViewController
-(void)methodCallCustomView{
}
- (IBAction)draw:(id)sender{
[self methodCallCustomView];
}
So you want the drawRect: method to be called when you press a button? If so, send the message setNeedsDisplay to the view that has the drawRect: code.
I need to draw an hexagon and fill it with a color build with an Image as pattern.
I did:
CGContextSaveGState(context);
CGContextSetLineCap(context, kCGLineCapRound);
CGContextSetFillColorWithColor(context, [[UIColor colorWithPatternImage:[UIImage imageNamed:#"patternerba.png"]] CGColor]);
CGContextSetStrokeColorWithColor(context, [[UIColor blackColor] CGColor]);
CGContextSetLineWidth(context, 3.0);
// drawing hexagon here...
CGContextStrokePath(context);
CGContextFillPath(context);
[[NSString stringWithFormat:#"Foo"] drawAtPoint:innerRect.origin withFont:[UIFont fontWithName:#"Helvetica" size:16]];
CGContextRestoreGState(context);
But depending from the order of CGContextStrokePath and CGContextFillPath, I get an hexagon bordered but not filled or filled but not bordered. How can I fix this?
Try
CGContextDrawPath(context, kCGPathFillStroke);
Instead of
CGContextStrokePath(context);
CGContextFillPath(context);
Either use
CGContextDrawPath(context, kCGPathFillStroke);
as sch suggested, or draw the hexagon again before calling FillPath. StrokePath and FillPath remove the path that you have added to the context, thus the next call will silently fail without a path.
CGPathRef path = /* drawing hexagon here */;
CGContextAddPath(context, path);
CGContextStrokePath(context);
CGContextAddPath(context, path);
CGContextFillPath(context);
Note: the two segments of code are not equivalent and gives different result.