问题
I am working on a drawing application, I am using CGlayers for drawing, So I open my canvas for drawing on click of a button,
I am using UIBezierPath and then converting it to CGPath in touchesMoved below and then using it to draw
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
if (ctr == 4)
{
m_touchMoved = true;
self.currentPath = [[DrawingPath alloc] init];
[self.currentPath setPathColor:self.lineColor];
self.currentPath.pathWidth = [NSString stringWithFormat:@"%f",self.lineWidth];
pts[3] = midPoint(pts[2], pts[4]);// move the endpoint to the middle of the line joining the second control point of the first Bezier segment and the first control point of the second Bezier segment
[self.currentPath.path moveToPoint:pts[0]];
[self.currentPath.path addCurveToPoint:pts[3] controlPoint1:pts[1] controlPoint2:pts[2]];
CGPathRef cgPath = self.currentPath.path.CGPath;
mutablePath = CGPathCreateMutableCopy(cgPath);
[self setNeedsDisplay];
pts[0] = pts[3];
pts[1] = pts[4];
ctr = 1;
}
}
This is my drawRect method
- (void)drawRect:(CGRect)rect
{
switch (m_drawStep)
{
case DRAW:
{
CGContextRef context = UIGraphicsGetCurrentContext();//Get a reference to current context(The context to draw)
if(currentDrawingLayer == nil)
{
CGFloat scale = self.contentScaleFactor;
CGRect bounds = CGRectMake(0, 0, self.bounds.size.width * scale, self.bounds.size.height * scale);
CGLayerRef layer = CGLayerCreateWithContext(context, bounds.size, NULL);
CGContextRef layerContext = CGLayerGetContext(layer);
CGContextScaleCTM(layerContext, scale, scale);
//currentDrawingLayer = layer;
[self setCurrentDrawingLayer:layer];
CGLayerRelease(currentDrawingLayer);
}
CGContextRef layerContext = CGLayerGetContext(currentDrawingLayer);
CGContextBeginPath(layerContext);
CGContextAddPath(layerContext, mutablePath);
CGContextSetLineWidth(layerContext, self.lineWidth);
CGContextSetLineCap(layerContext, kCGLineCapRound);
CGContextSetLineJoin(layerContext, kCGLineJoinRound);
CGContextSetAllowsAntialiasing(layerContext, YES);
CGContextSetShouldAntialias(layerContext, YES);
CGContextSetStrokeColorWithColor(layerContext, self.lineColor.CGColor);
CGContextSetFillColorWithColor(layerContext, self.lineColor.CGColor);
CGContextSetBlendMode(layerContext,kCGBlendModeNormal);
CGContextStrokePath(layerContext);
CGPathRelease(mutablePath);
CGContextDrawLayerInRect(context, self.bounds, currentDrawingLayer );
}
break;
}
I have manually created setter method
-(void)setCurrentDrawingLayer:(CGLayerRef)layer
{
CGLayerRetain(layer);
CGLayerRelease(currentDrawingLayer);
currentDrawingLayer = layer;
}
Now when user clicks on savebutton, I get image out of the canvas this way
-(void)getImageFromCanvas
{
UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO,0.0);//Creates a bitmap based graphics context with
//specified options
[self.layer renderInContext:UIGraphicsGetCurrentContext()];//Renders the reciever and its layers into specified
//context.
m_curImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();//Removes the current context from top of stack
if(currentDrawingLayer)
{
CGLayerRelease(currentDrawingLayer);
}
[m_delegate performSelectorOnMainThread:@selector(getCanVasViewImage:)
withObject:m_curImage
waitUntilDone:NO];
}
I get the image and show it on a grid on the screen with resized image, But when I perform these operations, my memory usage always spikes up, and it is not decreasing,here is the screen shot after creating three drawings
To resize image , I use this, I run this in a separate thread
dispatch_async(dispatch_get_global_queue(0,0), ^{
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
[image1 drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
});
memory goes on increasing, and finally after creating some 30 drawings, my app crashes, because memory spikes upto 550MB
So, I am not understanding where I am going wrong, How I can manage memory issues while drawing.
回答1:
Your mutablePath
leak, because you release the previous one in -drawRect:
(and only if m_drawStep == DRAW
). As -setNeedDisplay
just marks the view as needing to be redrawn.
-drawRect:
is only send on the next drawing cycle, so several -touchesMoved:withEvent:
may append between, drawing cycles.
There is also some leak, that can happen when m_drawStep != DRAW
.
So remove CGPathRelease(mutablePath)
from -drawRect:
method and release it in -touchesMoved:withEvent:
CGPathRef cgPath = self.currentPath.path.CGPath;
CGPathRelease(mutablePath);
mutablePath = CGPathCreateMutableCopy(cgPath);
[self setNeedsDisplay];
Also release the CGLayerRef
you create after setting it in -setCurrentDrawingLayer:
because you retain it in -setCurrentDrawingLayer:
.
if(currentDrawingLayer == nil)
{
// ...
CGLayerRef layer = CGLayerCreateWithContext(context, bounds.size, NULL); // layer is created, refCount == 1
// ...
[self setCurrentDrawingLayer:layer]; // layer is retained by -setCurrentDrawingLayer:, refCount == 2
CGLayerRelease(layer); // release layer, refCount == 1
// without it the previous release layer refCount still == 2, so in -setCurrentDrawingLayer:
// CGLayerRelease(currentDrawingLayer) decrement refCount to 1 and leak...
}
来源:https://stackoverflow.com/questions/22424743/memory-management-in-coregraphics-ios