iphone开发生成不规则的形状

转自:http://wsqwsq000.iteye.com/blog/1452484

生成一个不规则图形的方式,比如下面的效果:
需要将文字部分用多边形圈起来。这里做了一个多边形的图,然后填充为黑色,设置了alpha透明度,就产生了这样的效果。
代码如下:

- (void)loadView {
    [[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation: UIStatusBarAnimationSlide];
    UIImage *image=[UIImage imageNamed:@"1.jpg"];
 
    UIImageView *backView=[[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    backView.image=image;
    backView.alpha=0.6;
 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(nil,768,1024,8,0,
                                                 colorSpace,kCGImageAlphaPremultipliedLast);
    CFRelease(colorSpace);
 
    UIImageView *contentView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    CGColorRef fillColor = [[UIColor blackColor] CGColor];
    CGContextSetFillColor(context, CGColorGetComponents(fillColor));
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, 160.0f, 230.0f);
    CGContextAddLineToPoint(context, 600.0f, 230.0f);
    CGContextAddLineToPoint(context, 600.0f, 100.0f);
    CGContextAddLineToPoint(context, 370.0f, 50.0f);
    CGContextAddLineToPoint(context, 200.0f, 100.0f);
    CGContextClosePath(context);
    CGContextFillPath(context);
 
    contentView.image=[[UIImage alloc] initWithCGImage:CGBitmapContextCreateImage(context)];
    contentView.alpha=0.3;
    CGContextRelease(context);
 
    self.view=[[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    [self.view addSubview:backView];
    [self.view addSubview:contentView];
 
 
    [backView release];
    [contentView release];
    [image release];
}

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