UIImage得一个Category, Resizes(调整尺寸)

写在最前边: 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 (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