返回一张自由拉伸的图片

#import <UIKit/UIKit.h>

@interface UIImage (YKD)
/**
 *  加载图片
 *
 *  @param imageName 图片名
 */
+ (UIImage *)imageWithName:(NSString *)imageName;

/**
 *  返回一张自由拉伸的图片
 */
+ (UIImage *)resizedImageWithName:(NSString *)name;

/**
 *  按比例返回一张拉伸后的图片
 */
+ (UIImage *)resizedImageWithName:(NSString *)name left:(CGFloat)left top:(CGFloat)top;
@end

#import "UIImage+YKD.h"
//判断是否为iOS 7
#define iOS7 ([[UIDevice currentDevice].systemVersion doubleValue] >= 7.0)


@implementation UIImage (YKD)

+ (UIImage *)imageWithName:(NSString *)imageName
{
    if (iOS7) {
        NSString *newName = [imageName stringByAppendingString:@"_os7"];
        UIImage *image = [UIImage imageNamed:newName];
        if (image == nil) {
            image = [UIImage imageNamed:imageName];
        }
        return image;
    }
    //非iOS 7
    return [UIImage imageNamed:imageName];
}

+ (UIImage *)resizedImageWithName:(NSString *)name
{
    return [self resizedImageWithName:name left:0.5 top:0.5];
}

+ (UIImage *)resizedImageWithName:(NSString *)name left:(CGFloat)left top:(CGFloat)top
{
    UIImage *image = [self imageNamed:name];
    return [image stretchableImageWithLeftCapWidth:image.size.width * left topCapHeight:image.size.height * top];
}

@end