UIImage得一个Category, Resizes(调整尺寸)

在最前边: Category得用法很方便, 举例来说: 新建一个Class文件, 文件名随意需要建立UIImage得Category就按照如下格式添加函数,括号内名称随意, 这种格式, 编译器即认为是一个Category
@interface UIImage (xxx)
@end

@implementation UIImage (xxx)
@end

完整代码如下, 用法见附件Sample Code:

@interface UIImage (Category)
/*
* Resizes and/or rotates an image.
*/
- (UIImage*)transformWidth:(CGFloat)width 
                                  height:(CGFloat)height;
@end
 
@implementation UIImage (Category)
 
- (UIImage*)transformWidth:(CGFloat)width 
                    height:(CGFloat)height {
     
    CGFloat destW = width;
    CGFloat destH = height;
    CGFloat sourceW = width;
    CGFloat sourceH = height;
         
    CGImageRef imageRef = self.CGImage;
    CGContextRef bitmap = CGBitmapContextCreate(NULL, 
                                                destW, 
                                                destH,
                                                CGImageGetBitsPerComponent(imageRef), 
                                                4*destW, 
                                                CGImageGetColorSpace(imageRef),
                                                (kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst));
     
    CGContextDrawImage(bitmap, CGRectMake(0, 0, sourceW, sourceH), imageRef);
     
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage *result = [UIImage imageWithCGImage:ref];
    CGContextRelease(bitmap);
    CGImageRelease(ref);
     
    return result;
}
@end

 

CategorySampleViewController.m


NSString *imagePath = [[NSBundle mainBundle] pathForResource:@"XcodeCrash" ofType:@"png"];    
    UIImage *image = [[UIImage alloc] initWithContentsOfFile:imagePath];
       UIImage *newImage = [image transformWidth:80.f height:240.f];
    UIImageView *imageView = [[UIImageView alloc] initWithImage:newImage];
        [newImage release];
    [image release];
    [self.view addSubview:imageView];
    [imageView release];