Quartz 2D 常用简单功能汇总

跑马灯

跑马灯, 就是类似于电子屏幕上面无限滚动的广告效果。实现原理很简单，就是开启一个定时器，实时的刷新，即调用[self setNeedsDisplay]进行重绘，如有不理解的，请参考我上一节的博客，请点击这里。跑马灯实现的代码大致如下:

- (void)awakeFromNib {
    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(setNeedsDisplay)];
    
    [link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}

- (void)drawRect:(CGRect)rect {
    CGRect currentRect = self.frame;
    
    currentRect.origin.x++;
    
    if(currentRect.origin.x >= [UIScreen mainScreen].bounds.size.width){
        currentRect.origin.x = -self.frame.size.width;
    }
    
    self.frame = currentRect;
}

这里的定时器最好选用CADisplayLink, 因为刷新频率比较快。

图片水印

效果图：

实现思路，要有一个背景图片，一个水印图片，应该还告诉水印图片的位置，所以设计的代码大致如下：

+ (UIImage *)imageWaterMarkWithBgImage:(NSString *)bg waterImage:(NSString *)waterImage waterImagePosition:(CGPoint)position
{
    UIImage *bgImage = [UIImage imageNamed:bg];
    
    // 获取位图上下文
    UIGraphicsBeginImageContextWithOptions(bgImage.size, NO, 0.0);
    
    // 将图片画到上下文
    [bgImage drawInRect:CGRectMake(0, 0, bgImage.size.width, bgImage.size.height)];
    
    UIImage *logo = [UIImage imageNamed:waterImage];
    CGFloat logoW = logo.size.width;
    CGFloat logoH = logo.size.height;
    CGFloat logoX = bgImage.size.width - logoW - position.x;
    CGFloat logoY = bgImage.size.height - logoH - position.y;
    
    [logo drawInRect:CGRectMake(logoX, logoY, logoW, logoH)];
    
    // 从上下文中取出图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    // 结束上下文
    UIGraphicsEndImageContext();
    
    return newImage;
}

自定义圆角图片(也可以用layer实现)

效果图：

实现思路：1.图片；2.图片边框；3.边框颜色

+ (UIImage *)imageRoundedWithName:(NSString *)name borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor
{
    UIImage *image = [UIImage imageNamed:name];
    
    CGFloat drawLen = image.size.width + borderWidth * 2;
    
    CGFloat bigRadius = drawLen * 0.5;
    CGFloat smallRadius = image.size.width * 0.5;
    CGSize paintSize = CGSizeMake(drawLen, drawLen);
    
    // 确定画图版大小
    UIGraphicsBeginImageContextWithOptions(paintSize, NO, 0.0);
    
    // 获取上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    
    // 画圆
    CGContextAddArc(ctx, bigRadius, bigRadius, bigRadius, 0, M_PI * 2, 0);
    
    [borderColor set];
    
    CGContextFillPath(ctx);
    
    // 通过裁切重新定义绘制区域
    CGContextAddArc(ctx, bigRadius, bigRadius, smallRadius, 0, M_PI * 2, 0);
    CGContextClip(ctx);
    
    // 在裁切的圆形区域放置图片(随着borderWidth的改变，裁切圆会等比例缩放)
    [image drawInRect:CGRectMake(borderWidth, borderWidth, image.size.width, image.size.height)];
    
    // 获取上下文中的图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    return newImage;
}

屏幕截图

+ (UIImage *)imageWithView:(UIView *)view {
    UIGraphicsBeginImageContextWithOptions(view.frame.size, NO, 0.0);
    
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    
    [view.layer renderInContext:ctx];
    
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    return newImage;
}