為了防止工程師泄露用戶信息，我們有個需求是在列表上面添加水印。我封裝了這個視圖分享出來。

水印效果圖.png

watermarkView.h

#import <UIKit/UIKit.h>

@interface watermarkView : UIImageView

/**
 設置水印

 @param frame 水印大小
 @param markText 水印顯示的文字
 */
- (instancetype)initWithFrame:(CGRect)frame WithText:(NSString *)markText;

@end

watermarkView.m

#import "watermarkView.h"

#define HORIZONTAL_SPACE 30//水平間距
#define VERTICAL_SPACE 50//豎直間距
#define CG_TRANSFORM_ROTATION (M_PI_2 / 3)//旋轉角度(正旋45度 || 反旋45度)

@implementation watermarkView

- (instancetype)initWithFrame:(CGRect)frame WithText:(NSString *)markText{
    if(self = [super initWithFrame:frame]){
        
        UIFont *font = [UIFont systemFontOfSize:14];
        
        UIColor *color = YTHColorAlpha(152, 152, 152, 0.1);
        
        //原始image的寬高
        CGFloat viewWidth = frame.size.width;
        CGFloat viewHeight = frame.size.height;
        
        //為了防止圖片失真，繪制區(qū)域寬高和原始圖片寬高一樣
        UIGraphicsBeginImageContext(CGSizeMake(viewWidth, viewHeight));
        
        //sqrtLength：原始image的對角線length。在水印旋轉矩陣中只要矩陣的寬高是原始image的對角線長度，無論旋轉多少度都不會有空白。
        CGFloat sqrtLength = sqrt(viewWidth*viewWidth + viewHeight*viewHeight);
        //文字的屬性
        NSDictionary *attr = @{
                               //設置字體大小
                               NSFontAttributeName: font,
                               //設置文字顏色
                               NSForegroundColorAttributeName :color,
                               };
        NSString* mark = markText;
        NSMutableAttributedString *attrStr = [[NSMutableAttributedString alloc] initWithString:mark attributes:attr];
        //繪制文字的寬高
        CGFloat strWidth = attrStr.size.width;
        CGFloat strHeight = attrStr.size.height;
        
        //開始旋轉上下文矩陣，繪制水印文字
        CGContextRef context = UIGraphicsGetCurrentContext();
        
        //將繪制原點（0，0）調整到原image的中心
        CGContextConcatCTM(context, CGAffineTransformMakeTranslation(viewWidth/2, viewHeight/2));
        //以繪制原點為中心旋轉
        CGContextConcatCTM(context, CGAffineTransformMakeRotation(CG_TRANSFORM_ROTATION));
        //將繪制原點恢復初始值，保證當前context中心和源image的中心處在一個點(當前context已經(jīng)旋轉，所以繪制出的任何layer都是傾斜的)
        CGContextConcatCTM(context, CGAffineTransformMakeTranslation(-viewWidth/2, -viewHeight/2));
        
        //計算需要繪制的列數(shù)和行數(shù)
        int horCount = sqrtLength / (strWidth + HORIZONTAL_SPACE) + 1;
        int verCount = sqrtLength / (strHeight + VERTICAL_SPACE) + 1;
        
        //此處計算出需要繪制水印文字的起始點，由于水印區(qū)域要大于圖片區(qū)域所以起點在原有基礎上移
        CGFloat orignX = -(sqrtLength-viewWidth)/2;
        CGFloat orignY = -(sqrtLength-viewHeight)/2;
        
        //在每列繪制時X坐標疊加
        CGFloat tempOrignX = orignX;
        //在每行繪制時Y坐標疊加
        CGFloat tempOrignY = orignY;
        for (int i = 0; i < horCount * verCount; i++) {
            [mark drawInRect:CGRectMake(tempOrignX, tempOrignY, strWidth, strHeight) withAttributes:attr];
            if (i % horCount == 0 && i != 0) {
                tempOrignX = orignX;
                tempOrignY += (strHeight + VERTICAL_SPACE);
            }else{
                tempOrignX += (strWidth + HORIZONTAL_SPACE);
            }
        }
        //根據(jù)上下文制作成圖片
                UIImage *finalImg = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        CGContextRestoreGState(context);
        
        self.image = finalImg;
    }
    
    return self;
}

-(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{
    
    //1.判斷自己能否接收事件
    if(self.userInteractionEnabled == NO || self.hidden == YES || self.alpha <= 0.01) {
        return nil;
    }
    //2.判斷當前點在不在當前View.
    if (![self pointInside:point withEvent:event]) {
        return nil;
    }
    //3.從后往前遍歷自己的子控件.讓子控件重復前兩步操作,(把事件傳遞給,讓子控件調用hitTest)
    int count = (int)self.subviews.count;
    for (int i = count - 1; i >= 0; i--) {
        //取出每一個子控件
        UIView *chileV =  self.subviews[I];
        //把當前的點轉換成子控件坐標系上的點.
        CGPoint childP = [self convertPoint:point toView:chileV];
        UIView *fitView = [chileV hitTest:childP withEvent:event];
        //判斷有沒有找到最適合的View
        if(fitView){
            return fitView;
        }
    }
    
    //4.沒有找到比它自己更適合的View.那么它自己就是最適合的View
    return self;
}

//作用:判斷當前點在不在它調用View,(誰調用pointInside,這個View就是誰)
//什么時候調用:它是在hitTest方法當中調用的.
//注意:point點必須得要跟它方法調用者在同一個坐標系里面
-(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event{
    NSLog(@"%s",__func__);
    return NO;
}

使用方法

   //加水印
    watermarkView *watermark = [[watermarkView alloc] initWithFrame:CGRectMake(0, 0, KScreenW, KScreenH) WithText:@"測試"];
    [self.view addSubview:watermark];