Quartz 2D 实例：Watermark

最新推荐文章于 2025-05-14 00:15:00 发布

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#quartz #watermark #水印

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本文介绍了一个简单的 iOS 应用程序如何使用 Objective-C 为 UIImage 添加文本水印的方法。通过自定义 UIImage 的分类，实现了在图片底部居中位置添加白色、加粗且字号为 25 的水印文字。

UIImage+Watermark.h

#import <UIKit/UIKit.h>

@interface UIImage (Watermark)

- (UIImage *)watermarkImageWithText:(NSString *)text;

@end

UIImage+Watermark.m

#import "UIImage+Watermark.h"

@implementation UIImage (Watermark)

- (UIImage *)watermarkImageWithText:(NSString *)text
{
    //1.取到上下文
    UIGraphicsBeginImageContext(self.size);

    //2.绘制图片
    [self drawInRect:CGRectMake(0, 0, self.size.width, self.size.height)];

    //3.绘制水印文字
    CGRect textRect = CGRectMake(0, self.size.height - 30, self.size.width, 30);

    NSMutableParagraphStyle *style = [[NSMutableParagraphStyle defaultParagraphStyle] mutableCopy];
    style.alignment = NSTextAlignmentCenter;

    NSDictionary *attr = @{
                           NSFontAttributeName: [UIFont boldSystemFontOfSize:25],
                           NSParagraphStyleAttributeName: style,
                           NSForegroundColorAttributeName: [UIColor whiteColor]
                           };
//    [[UIColor whiteColor] set];
    [text drawInRect:textRect withAttributes:attr];

    //4.获取到绘制完成的图片
    UIImage *watermarkedImage = UIGraphicsGetImageFromCurrentImageContext();

    //5.结束在图片上的绘制
    UIGraphicsEndImageContext();

    return watermarkedImage;
}

@end

ViewController.m

#import "ViewController.h"
#import "UIImage+Watermark.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

   //水印
    UIImage *originImage = [UIImage imageNamed:@"屏幕快照 2015-04-04 16.21.17.png"];

    UIImage *watermarkedImage = [originImage watermarkImageWithText:@"Mainning.blog"];

    UIImageView *imgView = [[UIImageView alloc] initWithImage:watermarkedImage];
    imgView.frame = self.view.bounds;

    [self.view addSubview:imgView];
}

@end

这里写图片描述