iOS開發(fā)之在列表上方添加水印的方法

#import <UIKit/UIKit.h>

@interface watermarkView : UIImageView

/**
 設(shè)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

#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(zhuǎn)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?qū)捀吆驮紙D片寬高一樣
  UIGraphicsBeginImageContext(CGSizeMake(viewWidth, viewHeight));
  
  //sqrtLength：原始image的對角線length。在水印旋轉(zhuǎn)矩陣中只要矩陣的寬高是原始image的對角線長度，無論旋轉(zhuǎn)多少度都不會有空白。
  CGFloat sqrtLength = sqrt(viewWidth*viewWidth + viewHeight*viewHeight);
  //文字的屬性
  NSDictionary *attr = @{
        //設(shè)置字體大小
        NSFontAttributeName: font,
        //設(shè)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(zhuǎn)上下文矩陣，繪制水印文字
  CGContextRef context = UIGraphicsGetCurrentContext();
  
  //將繪制原點（0，0）調(diào)整到原image的中心
  CGContextConcatCTM(context, CGAffineTransformMakeTranslation(viewWidth/2, viewHeight/2));
  //以繪制原點為中心旋轉(zhuǎn)
  CGContextConcatCTM(context, CGAffineTransformMakeRotation(CG_TRANSFORM_ROTATION));
  //將繪制原點恢復(fù)初始值，保證當(dāng)前context中心和源image的中心處在一個點(當(dāng)前context已經(jīng)旋轉(zhuǎn)，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(chǔ)上移
  CGFloat orignX = -(sqrtLength-viewWidth)/2;
  CGFloat orignY = -(sqrtLength-viewHeight)/2;
  
  //在每列繪制時X坐標(biāo)疊加
  CGFloat tempOrignX = orignX;
  //在每行繪制時Y坐標(biāo)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(dāng)前點在不在當(dāng)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(fù)前兩步操作,(把事件傳遞給,讓子控件調(diào)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(dāng)前的點轉(zhuǎn)換成子控件坐標(biāo)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(dāng)前點在不在它調(diào)用View,(誰調(diào)用pointInside,這個View就是誰)
//什么時候調(diào)用:它是在hitTest方法當(dāng)中調(diào)用的.
//注意:point點必須得要跟它方法調(diào)用者在同一個坐標(biāo)系里面
-(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event{
 NSLog(@"%s",__func__);
 return NO;
}

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