注：
如果想实现点击以下变换颜色可以加上如下代码：
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
//重绘
[self setNeedsDisplay];
}
8、绘制文字
- (void)drawRect:(CGRect)rect {
NSString *str = @"李峰峰博客：http://www.easck.com/";
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
//设置字体
dict[NSFontAttributeName] = [UIFont systemFontOfSize:30];
//设置颜色
dict[NSForegroundColorAttributeName] = [UIColor redColor];
//设置描边
dict[NSStrokeColorAttributeName] = [UIColor blueColor];
dict[NSStrokeWidthAttributeName] = @3;
//设置阴影
NSShadow *shadow = [[NSShadow alloc] init];
shadow.shadowColor = [UIColor greenColor];
shadow.shadowOffset = CGSizeMake(-2, -2);
shadow.shadowBlurRadius = 3;
dict[NSShadowAttributeName] = shadow;
//设置文字的属性
//drawAtPoint不会自动换行
//[str drawAtPoint:CGPointMake(0, 0) withAttributes:dict];
//drawInRect会自动换行
[str drawInRect:self.bounds withAttributes:dict];
}
运行效果：
9、加水印
//
// ViewController.m
// Quartz2DTest
//
// Created by 李峰峰 on 2017/2/6.
// Copyright © 2017年 李峰峰. All rights reserved.
//
#import "ViewController.h"
#import "MyView.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
UIImageView *myImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
[self.view addSubview:myImageView];
//生成一张图片
//0.加载图片
UIImage *oriImage = [UIImage imageNamed:@"test"];
//1.创建位图上下文(size:开启多大的上下文,就会生成多大的图片)
UIGraphicsBeginImageContext(oriImage.size);
//2.把图片绘制到上下文当中
[oriImage drawAtPoint:CGPointZero];
//3.绘制水印(虽说UILabel可以快速实现这种效果，但是我们也可以绘制出来)
NSString *str = @"李峰峰博客";
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
dict[NSFontAttributeName] = [UIFont systemFontOfSize:20];
dict[NSForegroundColorAttributeName] = [UIColor redColor];
[str drawAtPoint:CGPointZero withAttributes:dict];
//4.从上下文当中生成一张图片
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
//5.关闭位图上下文
UIGraphicsEndImageContext();
myImageView.image = newImage;
}
@end
运行效果：
