Ios 如何在持久画布上绘制并在视图中绘制?
我正在为iOS编写一个小的绘画应用程序。我正在对UIView ad进行子类化,在其drawRect:方法中执行计算。这一切都很好,直到我开始有很多对象(实际上是多段线),然后性能开始下降Ios 如何在持久画布上绘制并在视图中绘制?,ios,image,drawing,cgcontext,persistent,Ios,Image,Drawing,Cgcontext,Persistent,我正在为iOS编写一个小的绘画应用程序。我正在对UIView ad进行子类化,在其drawRect:方法中执行计算。这一切都很好,直到我开始有很多对象(实际上是多段线),然后性能开始下降 - (void)drawRect:(CGRect)rect { [super drawRect:rect]; CGContextRef imageContext = UIGraphicsGetCurrentContext(); int i, j; for(i = 0; i &
- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
CGContextRef imageContext = UIGraphicsGetCurrentContext();
int i, j;
for(i = 0; i < [_strokes count]; i++) {
NSMutableArray *stroke = [_strokes objectAtIndex:i];
if([stroke count] < 2) {
continue;
}
CGContextSetStrokeColorWithColor(imageContext, [[_penColours objectAtIndex:i] CGColor]);
for(j = 0; j < [stroke count]-1; j++) {
CGPoint line[] = {
[[stroke objectAtIndex:j] CGPointValue],
[[stroke objectAtIndex:j+1] CGPointValue]
};
CGContextSetLineWidth(imageContext, _brushSize);
CGContextSetLineCap(imageContext, kCGLineCapRound);
CGContextSetLineJoin(imageContext, kCGLineJoinRound);
CGContextAddLines(imageContext, line, 2);
CGContextStrokePath(imageContext);
}
}
CGContextFlush(imageContext);
}
看起来至少有一部分问题是你保留了你的图片,但你从来没有发布过它。每次为_image指定一个新值时,都会泄漏上一个映像,这会很快填满内存
除此之外,您可能应该在屏幕外的绘图中使用位图,而不是位图。您可以随时绘制图层,然后用-drawRect:method将其复制到屏幕上。我会尽快尝试,并让您知道,谢谢您的提示。您好,我刚刚花了四个小时试图了解如何在CGLayers上绘制,但我没能完成多少工作。有什么建议吗?
- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
UIGraphicsBeginImageContext(CGSizeMake(1024, 768));
CGContextRef imageContext = UIGraphicsGetCurrentContext();
if(_image != nil) {
CGContextDrawImage(imageContext, CGRectMake(0, 0, 1024, 768), [_image CGImage]);
}
int i, j;
for(i = 0; i < [_strokes count]; i++) {
NSMutableArray *stroke = [_strokes objectAtIndex:i];
if([stroke count] < 2) {
continue;
}
CGContextSetStrokeColorWithColor(imageContext, [[_penColours objectAtIndex:i] CGColor]);
for(j = [stroke count]-2; j < [stroke count]-1; j++) {
CGPoint line[] = {
[[stroke objectAtIndex:j] CGPointValue],
[[stroke objectAtIndex:j+1] CGPointValue]
};
CGContextSetLineWidth(imageContext, _brushSize);
CGContextSetLineCap(imageContext, kCGLineCapRound);
CGContextSetLineJoin(imageContext, kCGLineJoinRound);
CGContextAddLines(imageContext, line, 2);
CGContextStrokePath(imageContext);
}
}
_image = UIGraphicsGetImageFromCurrentImageContext();
[_image retain];
UIGraphicsEndImageContext();
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, CGRectMake(0, 0, 1024, 768), [_image CGImage]);
}