<12>保持原来的长宽比，生成一个缩略图

/*
 * 保持原来的长宽比，生成一个缩略图
 * &-image 待传入UIImage
 * &-size 待传入UIImage要改变图像的尺寸
 * 返回处理好的UIImage

 */

+ (UIImage *)thumbnailWithImageWithoutScale:(UIImage *)image size:(CGSize)siz/** * 保持原来的长宽比，生成一个缩略图 */

+ (UIImage *)thumbnailWithImageWithoutScale:(UIImage *)image size:(CGSize)size
{
    UIImage *newimage;
    if (nil == image) {
        newimage = nil;
    }
else{
        CGSize oldsize = image.size;
        CGRect rect;
        if (size.width/size.height > oldsize.width/oldsize.height) {
            rect.size.width = size.height*oldsize.width/oldsize.height;
            rect.size.height = size.height;
            rect.origin.x = (size.width - rect.size.width)/2;
            rect.origin.y = 0;
        }
        else{
            rect.size.width = size.width;
            rect.size.height = size.width*oldsize.height/oldsize.width;
            rect.origin.x = 0;
            rect.origin.y = (size.height - rect.size.height)/2;
        }
        UIGraphicsBeginImageContext(size);
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);
        UIRectFill(CGRectMake(0, 0, size.width, size.height));//clear background
        [image drawInRect:rect];
        newimage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    return newimage;
}