假如一個 圖片 

"http://XXXX/ftp/upload/2016/10/28/11/5812c0f5776a2.jpg?900X616"

想得到後面的寬高 可以

-(CGSize)imgSize:(NSString *)imgPath{
    
    CGSize sz;
    NSRange range = [imgPath rangeOfString:@"?"];
    if (range.location != NSNotFound) {
        NSString *sub_str = [imgPath substringFromIndex:range.location+1];
        NSArray *arr = [[sub_str  lowercaseString] componentsSeparatedByString:@"x"];
        sz.width = [arr[0] floatValue];
        sz.height = [arr[1] floatValue];
        return sz;
    }
    return CGSizeZero;
}