Is there any way to quit from drawRect: without refresh the current UIView?
For example:
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
CGContextSetLineWidth(context, 2);
CGContextMoveToPoint(context, 10.0, 30.0);
CGContextAddLineToPoint(context, 310.0, 30.0);
CGContextStrokePath(context);
//I would like to return from here and rollback all changes in drawRect:
}
Thanks!
If you haven't started drawing into the context, it might be possible to just return from drawRect:. You'd have to set the clearsContextBeforeDrawing property of the view to NO before.
After starting to draw in the context, the view/layer will always update its content.
Related
I followed another StackOverflow post that explains how i could override the draw method of a PDFAnnotation so i could draw a picture instead of a traditional PDFAnnotation.
But sadly i was not able to achieve that and the annotation that is drawn on top of my pdf is still a regular one.
This is the code that i used :
#implementation PDFImageAnnotation { UIImage * _picture;
CGRect _bounds;};
-(instancetype)initWithPicture:(nonnull UIImage *)picture bounds:(CGRect) bounds{
self = [super initWithBounds:bounds
forType:PDFAnnotationSubtypeWidget
withProperties:nil];
if(self){
_picture = picture;
_bounds = bounds;
}
return self;
}
- (void)drawWithBox:(PDFDisplayBox) box
inContext:(CGContextRef)context {
[super drawWithBox:box inContext:context];
[_picture drawInRect:_bounds];
CGContextRestoreGState(context);
UIGraphicsPushContext(context);
};
#end
Does someone know how i could override the draw method so i could draw a custom Annotation ?
Thank You !
ps: i also tried to followed the tutorial on the apple dev site.
UPDATE :
Now i'm able to draw pictures using CGContextDrawImage but i'm not able to flip coordinates back in place. when i do that mi pictures are not drawn and it seems that they are put outside of the page but i'm not sure.
This is my new code :
- (void)drawWithBox:(PDFDisplayBox) box
inContext:(CGContextRef)context {
[super drawWithBox:box inContext:context];
UIGraphicsPushContext(context);
CGContextSaveGState(context);
CGContextTranslateCTM(context, 0.0, _pdfView.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, _bounds, _picture.CGImage);
CGContextRestoreGState(context);
UIGraphicsPopContext();
}
I also tried to follow the tutorial on the Apple dev site.
Which one?
Custom Graphics
Adding Custom Graphics to a PDF
Because both include UIGraphicsPushContext(context) & CGContextSaveGState(context) calls, but your code doesn't. Do not blindly copy & paste examples, try to understand them. Read what these two calls do.
Fixed code:
- (void)drawWithBox:(PDFDisplayBox) box
inContext:(CGContextRef)context {
[super drawWithBox:box inContext:context];
UIGraphicsPushContext(context);
CGContextSaveGState(context);
[_picture drawInRect:_bounds];
CGContextRestoreGState(context);
UIGraphicsPopContext();
}
The image was drawn with CGRectMake(20, 20, 100, 100). It's upside down, because PDFPage coordinates are flipped (0, 0 = bottom/left). Leaving it as an exercise for OP.
Rotation
Your rotation code is wrong:
CGContextTranslateCTM(context, 0.0, _pdfView.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, _bounds, _picture.CGImage);
It's based on _pdfView bounds, but it should be based on the image bounds (_bounds). Here's the correct one:
- (void)drawWithBox:(PDFDisplayBox) box
inContext:(CGContextRef)context {
[super drawWithBox:box inContext:context];
UIGraphicsPushContext(context);
CGContextSaveGState(context);
CGContextTranslateCTM(context, _bounds.origin.x, _bounds.origin.y + _bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
[_picture drawInRect:CGRectMake(0, 0, _bounds.size.width, _bounds.size.height)];
CGContextRestoreGState(context);
UIGraphicsPopContext();
}
I have this code to color an area between an inside and outside boundary.
CGContextSaveGState(context);
CGContextAddRect(context, self.bounds);
CGContextAddPath(context, inlinePath);
CGContextEOClip(context);
CGContextAddPath(context, outlinePath);
CGContextClip(context);
CGContextSetFillColorWithColor(context, _myColor.CGColor);
CGContextFillRect(context, self.bounds);
CGContextRestoreGState(context);
This is part of a local routine drawChartInContext:.
It works great when I generate an image like this:
UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, 2.0);
[self drawChartInContext:UIGraphicsGetCurrentContext()];
UIImage* image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
But when I call it from drawRect I just get the whole outlinePath area filled with _myColor.
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
[self drawChartInContext:context];
}
What could be wrong?
Just figured it out. It was a combination of two oversights:
inlinePath had zero area (a special case that is valid)
myColor had 1.0 alpha (a configuration mistake).
I have the touchesBegan void before this which triggers this event,
but i need this line to show, wait for so many seconds, then disappear:
- (void)drawRect:(CGRect)rect {
// Drawing code
//Make a simple rectangle and fill background BLUE with half Opeque
CGContextRef context = UIGraphicsGetCurrentContext();
//[[UIColor blueColor] set];
//CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1.0);
//rect = CGRectMake(20, 20, 40, 40);
//CGContextFillRect(context, rect);
//Make a simple RED line from 0,0 to 100, 100 in a FRAME
//CGContextSetRGBFillColor(context, 100.0, 0.0, 0.0, 1.0);
[[UIColor redColor] set];
CGContextMoveToPoint(context, _spaceShip.center.x, _spaceShip.center.y);
CGContextAddLineToPoint( context, nextLocX, nextLocY);
CODE FOR MAKING THE LINE DISAPPEAR
}
Redraw the frame without that line would be the obvious solution.
Draw over it in the background color would be a less-pretty solution that might in some cases run faster.
I have a UIViewController which has a UIView in it and I want to draw a straight dotted line on it. What is the easiest and performant way to do this? How do I do this? It will just be a straight horizontal dotted line of width 150 with gray color. I've looked around and it seems that using
CGContextSetLineDash is the solution and here's what I have so far:
-(void) drawRect:(CGRect) rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 100);
CGFloat dashes[] = {1,1};
CGContextSetLineDash(context, 2.0, dashes, 2);
CGContextStrokePath(context);
}
CGContextStrokePath draws the current path, however, you never add any path to your context, so nothing is drawn.
Add the following two lines before your CGContextStrokePath call and you should see something:
CGContextMoveToPoint(context, 0, self.bounds.size.height * 0.5);
CGContextAddLineToPoint(context, self.bounds.size.width, self.bounds.size.height * 0.5);
If you haven't already set your stroke color, you should also add something like this (50% gray):
CGContextSetRGBStrokeColor(context, 0.5, 0.5, 0.5, 1.0);
I'm not sure if the result is really what you want, a 100 point dotted line with a pattern of {1, 1} will look more like an rectangle with a pinstripe pattern than like a dotted line. If you want your dots to be circles, you will have to draw those manually in some sort of loop.
Try this:
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGContextSetStrokeColorWithColor(context, color.CGColor);
CGContextSetLineWidth(context, 2.0);
CGFloat lengths[] = {0, 8};
CGContextSetLineCap(context, kCGLineCapRound);
CGContextSetLineDash(context, 0.0f, lengths, 2);
CGContextMoveToPoint(context, 10, 10);
CGContextAddLineToPoint(context, 200, 10);
CGContextStrokePath(context);
CGColorSpaceRelease(colorspace);
I have a UIImage I draw lines on it that follow the users finger. It's like a drawing board. This works perfectly when the UIImage is small, say 500 x 600, but if it's like 1600 x 1200, it gets really scratchy and laggy. Is there a way I can optimize this? This is my drawing code in touchesModed:
UIGraphicsBeginImageContext(self.frame.size);
[drawImageView.image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 15.0);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
//CGContextSetAlpha(UIGraphicsGetCurrentContext(), 0.5f);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
Thanks.
Instead of drawing the entire 1600X1200 frame at a single go, why not draw it as it's needed. What I mean is since you are drawing the entire frame (which resides in memory) you are having patchy performance.
Try CATiledLayer. Basically you need to draw a screen size only which your device is capable of, anything more than that as the user scrolls you need to draw it on the fly.
This is what is used in Google Maps on iPad or iPhone. Hope this helps...
Instead of creating a new context and drawing the current image into it every time a touch moves, create a context using CGBitmapContextCreate and reuse that context. All previous drawing will already be in the context, and you won't have to create a new context each time a touch moves.
- (CGContextRef)drawingContext {
if(!context) { // context is an instance variable of type CGContextRef
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
if(!colorSpace) return nil;
context = CGBitmapContextCreate(NULL, contextSize.width, contextSize.height,
8, contextSize.width * 32, colorSpace,
kCGImageAlphaPremultipliedFirst);
CGColorSpaceRelease(colorSpace);
if(!context) return nil;
CGContextConcatCTM(context, CGAffineTransformMake(1,0,0,-1,0,contextSize.height));
CGContextDrawImage(context, (CGRect){CGPointZero,contextSize}, drawImageView.image.CGImage);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 15.0);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
}
return context;
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
CGContextRef ctxt = [self drawingContext];
CGContextBeginPath(ctxt);
CGContextMoveToPoint(ctxt, lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(ctxt, currentPoint.x, currentPoint.y);
CGContextStrokePath(ctxt);
CGImageRef img = CGBitmapContextCreateImage(ctxt);
drawImageView.image = [UIImage imageWithCGImage:img];
CGImageRelease(img);
}
This code requires the instance variables CGContextRef context and CGSize contextSize. The context will need to be released in dealloc, and whenever you change its size.