按钮背景图片拉伸

    UIImageView *imageView = [[UIImageView alloc] init];
    imageView.frame = CGRectMake(50, 50, 200, 200);
   // imageView.image = [UIImage imageNamed:@"chat_send_nor"];
    
    [self.view addSubview:imageView];
    
    
    UIImage *image = [UIImage  imageNamed:@"chat_send_nor"];
//    image = [image resizableImageWithCapInsets:UIEdgeInsetsMake(30,30, 30,30) resizingMode:UIImageResizingModeStretch];
    
    image = [image stretchableImageWithLeftCapWidth:image.size.width * 0.5 topCapHeight:image.size.height *0.5];
    
    imageView.image = image;
    
    

 UIimage扩展

#import <UIKit/UIKit.h>

@interface UIImage (Extension)
+(UIImage *)resiableImage:(NSString *)name;
@end

#import "UIImage+Extension.h"

@implementation UIImage (Extension)

+(UIImage *)resiableImage:(NSString *)name
{
    UIImage *image = [self imageNamed:name];
    
    return [image stretchableImageWithLeftCapWidth:image.size.width * 0.5 topCapHeight:image.size.height *0.5];


}



@end

扩展方法点使用

//
//  ViewController.m
//  图片拉伸
#import "ViewController.h"
#import "UIImage+Extension.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UIImageView *imageView = [[UIImageView alloc] init];
    imageView.frame = CGRectMake(50, 50, 200, 200);
    imageView.image = [UIImage resiableImage:@"chat_send_nor"];
    
    [self.view addSubview:imageView];
    
//    
//    UIImage *image = [UIImage  imageNamed:@"chat_send_nor"];
////    image = [image resizableImageWithCapInsets:UIEdgeInsetsMake(30,30, 30,30) resizingMode:UIImageResizingModeStretch];
//    
//    //image = [image stretchableImageWithLeftCapWidth:image.size.width * 0.5 topCapHeight:image.size.height *0.5];
//    
//    imageView.image = image;
//    
    
    
}


@end