Question

我想创建一个路径。就像我触摸屏幕并在touchmove事件中绘制线条。当线条从起点开始相交时。使用任何颜色填充该路径。

现在在图像中看到我画了一条线。我只想检测线是否再次相交到起点。然后用我自己想要的颜色填充那条路径。另外我用核心图形绘制线但是它很慢在真实的设备上。你能告诉我一种提高速度的方法吗？

Answer 1

部首：

#import <UIKit/UIKit.h>

@interface myView : UIView {
    CGMutablePathRef path;
    CGPathRef drawingPath;
    CGRect start;
    BOOL outsideStart;
}

@end

实现：

#import "myView.h"

@implementation myView

- (id) init {
    if (self = [super init]) {
        self.userInteractionEnabled = YES;
        self.multipleTouchEnabled = NO;
    }
}

- (void) finishPath {
    if (drawingPath) {
        CGPathRelease(drawingPath);
    }
    CGPathCloseSubpath(path);
    drawingPath = CGPathCreateCopy(path);
    CGPathRelease(path);
    path = NULL;
    [self setNeedsDisplay];
    return;
}

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    path = CGPathCreateMutable();
    UITouch *t = [touches anyObject];
    CGPoint p = [t locationInView:self];
    start = CGRectZero;
    start.origin = p;
    start = CGRectInset(start,-10, -10);
    outsideStart = NO;
    CGPathMoveToPoint(path, NULL, p.x, p.y);
}

- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    if (!path) {
        return;
    }
    UITouch *t = [touches anyObject];
    CGPoint p = [t locationInView:self];
    if (CGRectContainsPoint(start,p)) {
        if (outsideStart) {
            [self finishPath];
        }
    } else {
        outsideStart = YES;
    }
    CGPathAddLineToPoint(path,NULL,p.x,p.y);
    [self setNeedsDisplay];
}

- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    if (!path) {
        return;
    }
    [self finishPath];
}

- (void) touchesCanceled:(NSSet *)touches withEvent:(UIEvent *)event {
    if (!path) {
        return;
    }
    CGPathRelease(path);
    path = NULL;
}

- (void) drawInRect:(CGRect)rect {
    CGContextRef g = UIGraphicsGetCurrentContext();
    if (drawingPath) {
        CGContextAddPath(g,drawingPath);
        [[UIColor redColor] setFill];
        [[UIColor blackColor] setStroke];
        CGContextDrawPath(g,kCGPathFillStroke);
    }
    if (path) {
        CGContextAddPath(g,path);
        [[UIColor blackColor] setStroke];
        CGContextDrawPath(g,kCGPathStroke);
    }
}

- (void) dealloc {
    if (drawingPath) {
        CGPathRelease(drawingPath);
    }
    if (path) {
        CGPathRelease(path);
    }
    [super dealloc];
}

@end

请注意，您可能希望执行某些操作，这样每次路径更改时您实际上都不会调用setNeedsDisplay。这可能会非常缓慢。建议包括使用NSTimer每隔x毫秒触发一次以检查是否需要重新显示，如果需要则重新显示，或者仅在触摸移动了很长的距离时重新绘制。

Answer 2

也许它对你有用link text

Answer 3

每次图像更改时，Core Graphics绝对不应该使用[self setNeedsDisplay]，这可能是您的代码在设备上如此慢的原因。绘图很慢。如果你使用OpenGL ES绘制线条，它会更快，但代价是更难以理解。

如何使用coregraphics创建路径？

3 个答案: