iOS性能问题的绘图应用程序 [英] drawing application for iOS performance issue
问题描述
我正在为iOS创建绘图应用程序.为了触摸,我使用了本教程中的代码: http://www.raywenderlich.com/18840/how-to-make-a-simple-drawing-app-with-uikit
I'm creating drawing application for iOS. To draw something with a touch I used a code from this tutorial: http://www.raywenderlich.com/18840/how-to-make-a-simple-drawing-app-with-uikit
我用于绘图的代码如下:
My code that I use for drawing is the following:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = NO;
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self.view];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
UIGraphicsBeginImageContext(self.view.frame.size);
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush );
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);
CGContextStrokePath(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
[self.tempDrawImage setAlpha:opacity];
UIGraphicsEndImageContext();
lastPoint = currentPoint;
NSLog(@"Moved");
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
if(!mouseSwiped) {
UIGraphicsBeginImageContext(self.view.frame.size);
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, opacity);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
UIGraphicsBeginImageContext(self.mainImage.frame.size);
[self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:opacity];
self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
self.tempDrawImage.image = nil;
UIGraphicsEndImageContext();
}
我的问题如下:该代码在模拟器和iPhone 5上都能正常运行,但是当我在iPad 2上运行它时,效果却不佳.我的意思是,移动触摸时,它每隔3秒钟或类似的操作就会在屏幕上绘制一次(不是连续的).而且,当我不动手指就继续移动手指时,app崩溃了.
My problem is the following: this code works good on simulator and on my iPhone 5, but when I run it on my iPad 2, it's not working good. I mean when the touch is moved it gets drawn on the screen only each 3 seconds or something like this (it's not continous). Moreover when I keep moving my finger without lifting my finger app crashes after sometime.
我想这是性能问题.但为什么?你知道我该如何解决吗?
I guess it's a performance issue. But why? Do you have any idea how can I fix it?
推荐答案
问题是您一直在调用[self.tempDrawImage.image drawInRect:]
.该调用在CPU上渲染图像,并且非常慢.您不必要地开始和结束图像上下文.改用此代码,我在iPad 2上对其进行了测试,并且运行顺利.
The problem is that you keep calling [self.tempDrawImage.image drawInRect:]
. This call renders an image on the CPU and is extremely slow. You're unnecessarily beginning and ending the image context. Use this code instead, I tested it on an iPad 2 and it works smoothly.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = NO;
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self.view];
UIGraphicsBeginImageContext(self.view.frame.size);
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
CGContextRef ctxt = UIGraphicsGetCurrentContext();
CGContextMoveToPoint(ctxt, lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(ctxt, currentPoint.x, currentPoint.y);
CGContextSetLineCap(ctxt, kCGLineCapRound);
CGContextSetLineWidth(ctxt, brush );
CGContextSetRGBStrokeColor(ctxt, red, green, blue, 1.0);
CGContextSetBlendMode(ctxt,kCGBlendModeNormal);
CGContextStrokePath(ctxt);
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
[self.tempDrawImage setAlpha:opacity];
lastPoint = currentPoint;
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesCancelled:touches withEvent:event];
UIGraphicsEndImageContext();
if(!mouseSwiped)
{
self.tempDrawImage.image = nil;
}
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
if(!mouseSwiped) {
UIGraphicsEndImageContext();
UIGraphicsBeginImageContext(self.view.frame.size);
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, opacity);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
UIGraphicsBeginImageContext(self.mainImage.frame.size);
[self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:opacity];
self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
self.tempDrawImage.image = nil;
UIGraphicsEndImageContext();
}
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