iOS图片拉伸的4种方法

//
// ViewController.m
// iOS图片拉伸总结
//
// Created by Sunshine on 15/6/29.
// Copyright (c) 2015年 YotrolZ. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
 [super viewDidLoad];

 // 创建一个按钮
 UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];

 // 设置按钮的frame
 btn.frame = CGRectMake(100, 300, 200, 50);

 // 加载图片
 UIImage *image = [UIImage imageNamed:@"chat_send_nor"];

 // 设置按钮的背景图片
 [btn setBackgroundImage:image forState:UIControlStateNormal];

 // 将按钮添加到控制器的view
 [self.view addSubview:btn];

}

- (void)didReceiveMemoryWarning {
 [super didReceiveMemoryWarning];
 // Dispose of any resources that can be recreated.
}

@end

// 系统会自动计算rightCapWidth
rightCapWidth = image.width - leftCapWidth - 1; 

// 系统会自动计算bottomCapHeight
bottomCapHeight = image.height - topCapHeight - 1

 // 加载图片
 UIImage *image = [UIImage imageNamed:@"chat_send_nor"];

 // 设置左边端盖宽度
 NSInteger leftCapWidth = image.size.width * 0.5;
 // 设置上边端盖高度
 NSInteger topCapHeight = image.size.height * 0.5;

 UIImage *newImage = [image stretchableImageWithLeftCapWidth:leftCapWidth topCapHeight:topCapHeight];

 // 设置按钮的背景图片
 [btn setBackgroundImage:newImage forState:UIControlStateNormal];

// 官方API说明
- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets NS_AVAILABLE_IOS(5_0); 
// create a resizable version of this image. the interior is tiled when drawn.
typedef struct UIEdgeInsets {
 CGFloat top, left, bottom, right; 
 // specify amount to inset (positive) for each of the edges. values can be negative to 'outset'
} UIEdgeInsets;

 // 加载图片
 UIImage *image = [UIImage imageNamed:@"chat_send_nor"];

 // 设置端盖的值
 CGFloat top = image.size.height * 0.5;
 CGFloat left = image.size.width * 0.5;
 CGFloat bottom = image.size.height * 0.5;
 CGFloat right = image.size.width * 0.5;

 UIEdgeInsets edgeInsets = UIEdgeInsetsMake(top, left, bottom, right);

 // 拉伸图片
 UIImage *newImage = [image resizableImageWithCapInsets:edgeInsets];

 // 设置按钮的背景图片
 [btn setBackgroundImage:newImage forState:UIControlStateNormal];

typedef NS_ENUM(NSInteger, UIImageResizingMode) {
 UIImageResizingModeTile, // 平铺模式，通过重复显示UIEdgeInsets指定的矩形区域来填充图片
 UIImageResizingModeStretch, // 拉伸模式，通过拉伸UIEdgeInsets指定的矩形区域来填充图片
};

 // 加载图片
 UIImage *image = [UIImage imageNamed:@"chat_send_nor"];

 // 设置端盖的值
 CGFloat top = image.size.height * 0.5;
 CGFloat left = image.size.width * 0.5;
 CGFloat bottom = image.size.height * 0.5;
 CGFloat right = image.size.width * 0.5;

 // 设置端盖的值
 UIEdgeInsets edgeInsets = UIEdgeInsetsMake(top, left, bottom, right);
 // 设置拉伸的模式
 UIImageResizingMode mode = UIImageResizingModeStretch;

 // 拉伸图片
 UIImage *newImage = [image resizableImageWithCapInsets:edgeInsets resizingMode:mode];

 // 设置按钮的背景图片
 [btn setBackgroundImage:newImage forState:UIControlStateNormal];