废话不多说，直接上代码。代码直接黏贴可用，自定义画板View。

//
// MMGraphicView.h
// yuxi-manager
//
// Created by Sven on 2017/6/28.
// Copyright © 2017年 ylink. All rights reserved.
//

import <UIKit/UIKit.h>

// 画布
typedef void(^returnSignPhotoBlock)(UIImage * img);
@interface MMGraphicView : UIView
{
CGPoint _start;
CGPoint _move;
CGMutablePathRef _path;
NSMutableArray _pathArray;
CGFloat _lineWidth;
UIColor _color;
}
@property (nonatomic,assign)CGFloat lineWidth;/< 线宽 /
@property (nonatomic,strong)UIColor color;/< 线的颜色 */
@property (nonatomic,strong)NSMutableArray pathArray;
@property(nonatomic,copy)returnSignPhotoBlock block;
-(UIImage)getDrawingImg;
@end

//
// MMGraphicView.m
// yuxi-manager
//
// Created by Sven on 2017/6/28.
// Copyright © 2017年 ylink. All rights reserved.
//

import "MMGraphicView.h"

@implementation MMGraphicView

• (UIViewController )viewController
  {
  for (UIView next = [self superview]; next; next = next.superview) {
  UIResponder *nextResponder = [next nextResponder];
  if ([nextResponder isKindOfClass:[UIViewController class]]) {
  return (UIViewController *)nextResponder;
  }
  }
  return nil;
  }

• (instancetype)initWithFrame:(CGRect)frame {
  if (self = [super initWithFrame:frame]) {
  _move = CGPointMake(0, 0);
  _start = CGPointMake(0, 0);
  _lineWidth = 2;
  _color = [UIColor redColor];
  _pathArray = [NSMutableArray array];

    //创建保存功能
    UIButton *but = [UIButton buttonWithType:UIButtonTypeSystem];
    but.frame = CGRectMake(0, self.bounds.size.height-60, 100, 60);
    [but setTitle:@"保存签名" forState:UIControlStateNormal];
    [but addTarget:self action:@selector(savePhoto) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:but];
    
    
    UIButton *undoBtn = [UIButton buttonWithType:UIButtonTypeSystem];
    undoBtn.frame = CGRectMake(110, self.bounds.size.height-60, 100, 60);
    [undoBtn setTitle:@"撤销" forState:UIControlStateNormal];
    [undoBtn addTarget:self action:@selector(undoBtnEvent) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:undoBtn];
    
    UIButton *clearBtn = [UIButton buttonWithType:UIButtonTypeSystem];
    clearBtn.frame = CGRectMake(220, self.bounds.size.height-60, 100, 60);
    [clearBtn setTitle:@"清除啊" forState:UIControlStateNormal];
    [clearBtn addTarget:self action:@selector(clearBtnEvent) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:clearBtn];
    
    
    UIButton * backBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    backBtn.frame = CGRectMake(330, self.bounds.size.height-60, 100, 60);
    [backBtn addTarget:self action:@selector(back) forControlEvents:UIControlEventTouchUpInside];
    [backBtn setTitle:@"返回" forState:UIControlStateNormal];
    [backBtn setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    [self addSubview:backBtn];
  

  } return self;}

-(void)back{

[[self viewController].navigationController popViewControllerAnimated:YES];}

• (void)drawRect:(CGRect)rect {
  // 获取图形上下文
  CGContextRef context = UIGraphicsGetCurrentContext();
  [self drawPicture:context]; //画图
  }

• (void)drawPicture:(CGContextRef)context {
  for (NSArray * attribute in _pathArray) {
  //将路径添加到上下文中
  CGPathRef pathRef = (__bridge CGPathRef)(attribute[0]);
  CGContextAddPath(context, pathRef);
  //设置上下文属性
  [attribute[1] setStroke];
  CGContextSetLineWidth(context, [attribute[2] floatValue]);
  //绘制线条
  CGContextDrawPath(context, kCGPathStroke);
  }
  }

• (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
  UITouch *touch = [touches anyObject];
  _path = CGPathCreateMutable(); //创建路径

NSArray *attributeArry = @[(__bridge id)(_path),_color,[NSNumber numberWithFloat:_lineWidth]];

[_pathArray addObject:attributeArry]; //路径及属性数组数组
_start = [touch locationInView:self]; //起始点
CGPathMoveToPoint(_path, NULL,_start.x, _start.y);}

• (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
  // 释放路径
  CGPathRelease(_path);}

• (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
  UITouch *touch = [touches anyObject];
  _move = [touch locationInView:self];
  //将点添加到路径上
  CGPathAddLineToPoint(_path, NULL, _move.x, _move.y);

[self setNeedsDisplay];
}

pragma mark --点击事件--

• (void)savePhoto {

if (_pathArray.count) {
    UIGraphicsBeginImageContext(self.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    UIRectClip(CGRectMake(0, 0, self.frame.size.width, self.frame.size.height-100));
    [self.layer renderInContext:context];
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

// UIImageWriteToSavedPhotosAlbum(image, self, nil, NULL);
UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), NULL);
self.block(image);
}
else{
UIAlertView* alert = [[UIAlertView alloc]initWithTitle:@"alert" message:@"请您先绘制图形" delegate:nil cancelButtonTitle:nil otherButtonTitles:@"确定", nil];

    [alert show];
    
}}

• (void)image: (UIImage *) image didFinishSavingWithError: (NSError *) error contextInfo: (NSString *)str{

NSString *msg = nil ;

if(error != NULL){
    
    msg = @"保存图片失败" ;
    
}else{
    
    msg = @"保存图片成功" ;
    
}

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"保存图片结果提示"
                      
                                                message:msg
                      
                                               delegate:self
                      
                                      cancelButtonTitle:@"确定"
                      
                                      otherButtonTitles:nil];

[alert show];

}

-(UIImage *)getDrawingImg{
if (_pathArray.count) {
UIGraphicsBeginImageContext(self.frame.size);
CGContextRef context = UIGraphicsGetCurrentContext();
UIRectClip(CGRectMake(0, 0, self.frame.size.width, self.frame.size.height));
[self.layer renderInContext:context];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    
    return image;
}
UIAlertView* alert = [[UIAlertView alloc]initWithTitle:@"alert" message:@"请您先绘制图形" delegate:nil cancelButtonTitle:nil otherButtonTitles:@"确定", nil];
[alert show];
return nil;}

-(void)undoBtnEvent
{
[_pathArray removeLastObject];
[self setNeedsDisplay];
}

-(void)clearBtnEvent
{
[_pathArray removeAllObjects];
[self setNeedsDisplay];
}

@end

很好用的封装，带删除上一步画笔、清楚所有轨迹、保存图片 、保存回调提醒、自定义画笔颜色、粗细大小等功能。如果帮到您，请点个👍~