1 - (void)drawRect:(CGRect)rect {2     [[UIColor redColor] set];3     UIRectFill(CGRectMake(0, 0, 100, 100));4 }

 1 - (void)drawRect:(CGRect)rect { 2     CGContextRef ctx = UIGraphicsGetCurrentContext(); 3     4     // 1.1创建第一个path 5     CGMutablePathRef linePath = CGPathCreateMutable(); 6     7     // 1.2.描绘path 8     CGPathMoveToPoint(linePath, NULL, 0, 0); 9     CGPathAddLineToPoint(linePath, NULL, 100, 100);10    11     // 1.3.添加linePath到上下文12     CGContextAddPath(ctx, linePath);13    14     // 2添加一个圆的path15     CGMutablePathRef circlePath = CGPathCreateMutable();16     CGPathAddEllipseInRect(circlePath, NULL, CGRectMake(0, 0, 50, 50));17     CGContextAddPath(ctx, circlePath);18    19     // 渲染上下文20     CGContextStrokePath(ctx);21    22     // 释放path23     CGPathRelease(linePath);24     CGPathRelease(circlePath);25 }

 1 // 2 //  MyImageView.h 3 //  MyImageView 4 // 5 //  Created by hellovoidworld on 14/12/31. 6 //  Copyright (c) 2014年 hellovoidworld. All rights reserved. 7 // 8  9 #import <UIKit/UIKit.h>10 11 @interface MyImageView : UIView12 13 @property(nonatomic, weak) UIImage *image;14 15 @end

 1 // 2 //  MyImageView.m 3 //  MyImageView 4 // 5 //  Created by hellovoidworld on 14/12/31. 6 //  Copyright (c) 2014年 hellovoidworld. All rights reserved. 7 // 8  9 #import "MyImageView.h"10 11 @implementation MyImageView12 13 - (void)setImage:(UIImage *)image {14     _image = image;15    16     // 重新设置了图片的时候，重绘17     [self setNeedsDisplay];18 }19 20 - (void)drawRect:(CGRect)rect {21     [self.image drawInRect:rect];22 }23 24 @end25  26 controller:27 - (void)viewDidLoad {28     [super viewDidLoad];29     // Do any additional setup after loading the view, typically from a nib.30    31     MyImageView *imageView = [[MyImageView alloc] init];32     imageView.frame = CGRectMake(0, 0, 200, 320);33     [self.view addSubview:imageView];34     imageView.image = [UIImage imageNamed:@"M4"];35 }

 1 // 2 //  MyTextView.h 3 //  MyTextField 4 // 5 //  Created by hellovoidworld on 14/12/31. 6 //  Copyright (c) 2014年 hellovoidworld. All rights reserved. 7 // 8  9 #import <UIKit/UIKit.h>10 11 @interface MyTextView : UITextView12 13 @property(nonatomic, copy) NSString *placeHolderText;14 15 @end

 1 // 2 //  MyTextView.m 3 //  MyTextField 4 // 5 //  Created by hellovoidworld on 14/12/31. 6 //  Copyright (c) 2014年 hellovoidworld. All rights reserved. 7 // 8  9 #import "MyTextView.h"10 11 @interface MyTextView() <UITextViewDelegate>12 13 /** 原来的文本颜色 */14 @property(nonatomic, weak) UIColor *originalTextColor;15 16 @end17 18 @implementation MyTextView19 20 // 重写初始化方法，设置代理21 - (instancetype)init {22     if (self = [super init]) {23         self.returnKeyType = UIReturnKeyDone;24         self.delegate = self;25     }26    27     return self;28 }29 30 // 重新设置了placeHolderText的时候要重绘一下控件31 - (void)setPlaceHolderText:(NSString *)placeHolderText {32     _placeHolderText = placeHolderText;33     [self setNeedsDisplay];34 }35 36 // 开始编辑，消除placeHolder37 - (BOOL)textViewShouldBeginEditing:(UITextView *)textView {38     if ([self.text isEqualToString:self.placeHolderText]) {39         self.text = nil;40         self.textColor = self.originalTextColor;41     }42    43     return YES;44 }45 46 // 结束编辑，如果文本为空，设置placeHolder47 - (void)textViewDidEndEditing:(UITextView *)textView {48     [self setNeedsDisplay];49 }50 51 - (void)drawRect:(CGRect)rect {52     if (self.text.length == 0) {53         self.text = self.placeHolderText;54         self.textColor = [UIColor grayColor];55     }56 }57 58 59 @end

 1 // 2 //  UIImage+HW.m 3 //  Watermark 4 // 5 //  Created by hellovoidworld on 14/12/31. 6 //  Copyright (c) 2014年 hellovoidworld. All rights reserved. 7 // 8  9 #import "UIImage+HW.h"10 11 @implementation UIImage(HW)12 13 + (instancetype) image:(NSString *) image withWatermark:(NSString *) watermark {14     // 取得背景图片15     UIImage *bgImage = [UIImage imageNamed:image];16    17     // 1.开启一个位图上下文18     UIGraphicsBeginImageContextWithOptions(bgImage.size, NO, 0.0);19    20     // 2.添加背景图片到位图上下文21     [bgImage drawInRect:CGRectMake(0, 0, bgImage.size.width, bgImage.size.height)];22    23     // 3.添加水印图片24     UIImage *watermarkImage = [UIImage imageNamed:watermark];25     CGFloat scale = 0.5;26     CGFloat margin = 50;27     CGFloat watermarkWidth = watermarkImage.size.width * scale;28     CGFloat watermarkHeight = watermarkImage.size.width *scale;29     CGFloat watermarkX = bgImage.size.width - watermarkWidth - margin;30     CGFloat watermarkY = bgImage.size.height - watermarkHeight - margin;31     [watermarkImage drawInRect:CGRectMake(watermarkX, watermarkY, watermarkWidth, watermarkHeight)];32    33    34     // 4.取得合成后的图片35     UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();36    37     // 5.关闭图文上下文38     UIGraphicsEndImageContext();39    40     return resultImage;41 }42 43 @end

 1 - (void)viewDidLoad { 2     [super viewDidLoad]; 3     // Do any additional setup after loading the view, typically from a nib. 4     5     UIImage *watermarkedImage = [UIImage image:@"M4" withWatermark:@"a9ec8a13632762d0092abc3ca2ec08fa513dc619"]; 6     7     UIImageView *imageView = [[UIImageView alloc] initWithImage:watermarkedImage]; 8     imageView.frame = CGRectMake(0, 0, 200, 320); 9     [self.view addSubview:imageView];10 }

1     // 压缩图片为PNG格式的二进制数据2     NSData *data =http://www.mamicode.com/ UIImagePNGRepresentation(watermarkedImage);3    4     // 写入文件5     NSString *path =[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"watermarkedImage.png"];6     NSLog(@"%@", path);7     [data writeToFile:path atomically:YES];

 1 /**  创建带有指定宽度和颜色边框的圆形头像图片 */ 2 + (instancetype) imageOfCircleHeadIcon:(NSString *) image withBorderWidth:(CGFloat) borderWidth borderColor:(UIColor *) borderColor { 3     //  取得图片 4     UIImage *headIconImage = [UIImage imageNamed:image]; 5     6     // 开启图片上下文 7     CGFloat backImageWidth = headIconImage.size.width + 2 * borderWidth; 8     CGFloat backImageHeight = headIconImage.size.height + 2 * borderWidth; 9     CGSize backImageSize = CGSizeMake(backImageWidth, backImageHeight);10     UIGraphicsBeginImageContextWithOptions(backImageSize, NO, 0.0);11    12     // 描绘背景大圆13     [borderColor set]; // 设置圆环颜色14     CGContextRef ctx = UIGraphicsGetCurrentContext();15     CGFloat backCircleRadius = backImageWidth * 0.5; // 大圆半径16     CGFloat backCircleX = backCircleRadius; // 大圆圆心X17     CGFloat backCircleY = backCircleRadius; // 大圆圆心Y18     CGContextAddArc(ctx, backCircleX, backCircleY, backCircleRadius, 0, M_PI * 2, 0);19     CGContextFillPath(ctx);20    21     // 描绘用来显示图片的小圆22     CGFloat frontCircleRadius = backCircleRadius - borderWidth; // 图片小圆半径23     CGFloat frontCircleX = backCircleX;24     CGFloat frontCircleY = backCircleY;25     CGContextAddArc(ctx, frontCircleX, frontCircleY, frontCircleRadius, 0, M_PI * 2, 0);26    27     // 裁剪（后面描绘的将会受到裁剪）28     CGContextClip(ctx);29    30     // 添加图片到上下文31     [headIconImage drawInRect:CGRectMake(borderWidth, borderWidth, headIconImage.size.width, headIconImage.size.height)];32    33     // 取得合成后的图片34     UIImage *headIconResultImage = UIGraphicsGetImageFromCurrentImageContext();35    36     // 关闭图片上下文37     UIGraphicsEndImageContext();38    39     return headIconResultImage;40 }

 1 /** 点击“屏幕截图” */ 2 - (IBAction)screenShotcut { 3     // 延迟截图， 防止截到的时按钮被按下的状态 4     dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ 5         6         UIView *view = self.view; 7         8         // 1.开启位图上下文 9         UIGraphicsBeginImageContextWithOptions(view.frame.size, NO, 0.0);10        11         // 2.渲染控制器view的layer到上下文12         [view.layer renderInContext:UIGraphicsGetCurrentContext()];13        14         // 3.从上下文取得图片15         UIImage *screenImage = UIGraphicsGetImageFromCurrentImageContext();16        17         // 4.结束上下文18         UIGraphicsEndImageContext();19        20         // 存储图片21         NSData *data =http://www.mamicode.com/ UIImagePNGRepresentation(screenImage);22         NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"screenShot.png"];23         NSLog(@"%@", path);24         [data writeToFile:path atomically:YES];    });25 26 }

 1 - (void)viewDidLoad { 2     [super viewDidLoad]; 3     // Do any additional setup after loading the view, typically from a nib. 4     5     // 开启图片上下文 6     CGFloat rowW = self.view.frame.size.width; 7     CGFloat rowH = 30; 8     UIGraphicsBeginImageContextWithOptions(CGSizeMake(rowW, rowH), NO, 0.0); 9    10     CGContextRef ctx = UIGraphicsGetCurrentContext();11     // 画色块背景12     [[UIColor redColor] set];13     CGContextAddRect(ctx, CGRectMake(0, 0, rowW, rowH));14     CGContextFillPath(ctx);15    16     // 画线17     [[UIColor greenColor] set];18     CGFloat lineWidth = 2;19     CGContextSetLineWidth(ctx, lineWidth);20     CGFloat lineX = 0;21     CGFloat lineY = rowH - lineWidth;22     CGContextMoveToPoint(ctx, lineX, lineY);23     CGContextAddLineToPoint(ctx, rowW - lineX, lineY);24     CGContextStrokePath(ctx);25    26     UIImage *image = UIGraphicsGetImageFromCurrentImageContext();27    28     // 使用平铺方式铺满屏幕29     [self.view setBackgroundColor:[UIColor colorWithPatternImage:image]];30    31     UIGraphicsEndImageContext();32 }