iOS:在UIImage上绘制NSString和边框

Question

我想在我已经拥有的UIImage上绘制一个NSString和一个边框.我发现了一个将NSString绘制为UIImage的方法,但是我需要它来绘制我提供的图像.

-(UIImage *)imageFromText:(NSString *)text
{
    // set the font type and size
    UIFont *font = [UIFont systemFontOfSize:20.0];  
    CGSize size  = [text sizeWithFont:font];

    // check if UIGraphicsBeginImageContextWithOptions is available (iOS is 4.0+)
    if (UIGraphicsBeginImageContextWithOptions != NULL)
        UIGraphicsBeginImageContextWithOptions(size,NO,0.0);
    else
        // iOS is < 4.0 
        UIGraphicsBeginImageContext(size);

    // optional: add a shadow, to avoid clipping the shadow you should make the context size bigger 
    //
    // CGContextRef ctx = UIGraphicsGetCurrentContext();
    // CGContextSetShadowWithColor(ctx, CGSizeMake(1.0, 1.0), 5.0, [[UIColor grayColor] CGColor]);

    // draw in context, you can use also drawInRect:withFont:
    [text drawAtPoint:CGPointMake(0.0, 0.0) withFont:font];

    // transfer image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();    

    return image;
}

如何修改此方法以提供我自己的背景图像,以及添加边框？

Answer 1

如果您在UIImageView中显示UIImage,您可以设置UIImageView.layer.delegate并使用如下内容:

- (void) drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
  CGContextSetFillColorWithColor(ctx, [[UIColor darkTextColor] CGColor]);

  UIGraphicsPushContext(ctx);

  [word drawAtPoint:CGPointMake(30.0f, 30.0f) 
           forWidth:200.0f 
           withFont:[UIFont boldSystemFontOfSize:32] 
      lineBreakMode:UILineBreakModeClip];

  UIGraphicsPopContext();
}

代码从添加文本到CALayer

边框很简单,只需使用CALayer属性:

imageview.layer.borderColor = [UIColor blackColor].CGColor;
imageview.sublayer.borderWidth = 2.0;