UITextField custom background and set padding

a.m

    [_loginBtn setBackgroundImage:[UIImage imageNamed:@"buttonlogin"] forState:UIControlStateNormal];
    
    UIImage *fieldBGImage = [[UIImage imageNamed:@"inputform"] stretchableImageWithLeftCapWidth:20 topCapHeight:20];
    [_userIDTxt setBorderStyle:UITextBorderStyleNone];
    [_userIDTxt setBackground:fieldBGImage];
    [_tinTxt setBorderStyle:UITextBorderStyleNone];
    [_tinTxt setBackground:fieldBGImage];
    
    UIView *paddingView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
    _userIDTxt.leftView = paddingView;
    _userIDTxt.leftViewMode = UITextFieldViewModeAlways;
    _tinTxt.leftView = paddingView;
    _tinTxt.leftViewMode = UITextFieldViewModeAlways;