使用TypeScript函数绑定Angular img src属性

我想从类型脚本函数绑定html标记img的src. 这是我的Html.

<button (click)="createBoard()"> Create Board</button>
<table>
 <tr *ngFor="let i of board; let a = index">
  <td *ngFor="let j of i; let b = index">
    <div class="bDefault">
      <img src="getImage(a,b)"  
      (click)="changeImg(a,b, $event)">
    </div>
  </td>
 </tr>
</table> 

这是我的Typescript .

size : number = 5;
board : number[][] = [];

createBoard(){
 this.board = new Array(this.size);
 for(let i=0; i<this.size; i++){
  this.board[i] = new Array(this.size);
  for(let j=0; j<this.size; j++){
    this.board[i][j] = 0;
  }
 }
}

getImage(i:any, j:any){
  if(this.board[i][j] == 0){
    return "../../../assets/oth/default.jpg";
  } else if(this.board[i][j] == 1){
    return "../../../assets/oth/bidak_hitam.jpg";
  } else {
    return "../../../assets/oth/bidak_putih.jpg";
  }
}

changeImg(i:any, j:any, event:Event){
  if(this.board[i][j] == 2){
    this.board[i][j]  = 0;
  } else {
    this.board[i][j] ++;
  }
}

在这段代码中，没有找到图像.有没有办法从打印或Angular 的函数中获取图像？