您可以使用 Destination Out 作为混合模式在 CGContext 上绘制文本。
这段代码似乎有效:
- (void)viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor greenColor];
UIFont* font = [UIFont fontWithName:@"Helvetica-Bold" size:18];
NSString* buttonText = @"BUTTON";
CGSize buttonSize = CGSizeMake(200, 50);
NSDictionary* textAttributes = @{NSFontAttributeName:font};
CGSize textSize = [buttonText sizeWithAttributes:textAttributes];
UIGraphicsBeginImageContextWithOptions(buttonSize, NO, [[UIScreen mainScreen] scale]);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(ctx, [UIColor redColor].CGColor);
UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, buttonSize.width, buttonSize.height)];
CGContextAddPath(ctx, path.CGPath);
CGContextFillPath(ctx);
CGContextSetBlendMode(ctx, kCGBlendModeDestinationOut);
CGPoint center = CGPointMake(buttonSize.width/2-textSize.width/2, buttonSize.height/2-textSize.height/2);
[@"BUTTON" drawAtPoint:center withAttributes:textAttributes];
UIImage* viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView* imgView = [[UIImageView alloc] initWithImage:viewImage];
[self.view addSubview:imgView];
}
顺便说一句,如果你想在 UIButton 中设置 UIImage 而不是仅仅将其添加到视图中:
UIButton* boton = [[UIButton alloc] initWithFrame:CGRectMake(50, 50, viewImage.size.width, viewImage.size.height)];
[boton setBackgroundColor:[UIColor clearColor]];
[boton setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
boton.titleLabel.font = font;
[boton setTitle:buttonText forState:UIControlStateNormal];
[boton setImage:viewImage forState:UIControlStateHighlighted];
[self.view addSubview:boton];