Add Background Image to UITableViewRowAction button

Question

I am working with UITableViewRowAction. My requirement is that on left swipe of a table cell, I should show 2 UITableViewRowAction button. I am able to achieve that by implementing -(NSArray *)tableView:(UITableView *)tableView editActionsForRowAtIndexPath:(NSIndexPath *)indexPath;. Here is the code for that

-(NSArray *)tableView:(UITableView *)tableView editActionsForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewRowAction *button = [UITableViewRowAction rowActionWithStyle:UITableViewRowActionStyleDefault title:@"Delete" handler:^(UITableViewRowAction *action, NSIndexPath *indexPath)
                                {
                                    NSLog(@"Action to perform with Button 1");
                                }];
    button.backgroundColor = [UIColor greenColor]; //arbitrary color
    UITableViewRowAction *button2 = [UITableViewRowAction rowActionWithStyle:UITableViewRowActionStyleDefault title:@"Edit" handler:^(UITableViewRowAction *action, NSIndexPath *indexPath)
                                 {
                                     NSLog(@"Action to perform with Button2!");
                                 }];
    button2.backgroundColor = [UIColor redColor]; //arbitrary color

    return @[button, button2];
}

Currently I am using some arbitrary color as background for button and button2.

But my requirement is to have a background image instead of some color. I went through the answer given here and tried and implemented it by adding

button.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"icon_ab_delete.png"]];

instead of

button.backgroundColor = [UIColor greenColor];

I have icon_ab_delete.png stored in my project. But, when I run my app I get a white color background with nothing on it. Something like this:

The button after edit which was suppose to be for delete shows nothing, and it does exist as I can still capture the event I am trying to do inside it's handler.

I want to know whether I am setting the background image correctly or is there some other way to do what I am trying to achieve?

Thanks in advance!