繪製畫布內部的圖像

Question

代碼：

function DrawLevel1() { 
    Pos = 1; 
    w = 84; 
    h = 84; 
    x = 28; 
    y = 28; 
    for (i = 0; i < cw; i += 28) { /// use += 

     ctx.drawImage(tankImg, 
        (Pos - 1) * w, /// x of source (use 0-based indexes) 
        0,   /// y of source 
        w,   /// width of source 
        h,   /// height of source 
        i,   /// x in destination (visible canvas) 
        y,   /// y, width and height of the resulting 
        w, h);  /// image 
     x += 28; 
     y += 28; 
    } 
} 

DrawLevel1（）;

圖像：

http://oi62.tinypic.com/148yf7.jpg http://oi62.tinypic.com/148yf7.jpg

帆布：<canvas id="MyCanvas" width="400" height="400"></canvas>

什麼，我試圖做的基本上是借鑑第一灰瓦一直畫布cw .notice的寬度的第一行我不能使用平鋪陣列並繪製它，這個函數並沒有畫任何東西，我想不出爲什麼有人能幫我請
jsfiddle：http://jsfiddle.net/seekpunk/B2nUs/36/

Answer 1

我修改代碼，這是我的jsfiddle http://jsfiddle.net/yalight/5cHQF/

function DrawLevel1() { 
    Pos = 1; 
    w = 84; 
    h = 84; 
    x = 28; 
    y = 28; 
    for (i = 0; i < cw; i += 28) { /// use += 
     for(j = 0; j< cw; j += 28) { 

      ctx.drawImage(tankImg, 
        0, /// x of source (use 0-based indexes) 
        0,   /// y of source 
        w,   /// width of source 
        h,   /// height of source 
        i,   /// x in destination (visible canvas) 
        j,   /// y, width and height of the resulting 
        w, h);  /// image 
      x += 28; 
      y += 28; 
     } 
    } 
} 

只畫第一行http://jsfiddle.net/yalight/FT8M2/：

function DrawLevel1() { 
    w = 84; 
    h = 84; 
    x = 28; 
    //y = 28; 
    for (i = 0; i < cw; i += x) { /// use += 
     ctx.drawImage(tankImg, 
      0,  /// x of source (use 0-based indexes) 
      0,  /// y of source 
      w,  /// width of source 
      h,  /// height of source 
      i,  /// x in destination (visible canvas) 
      0,  /// y, width and height of the resulting 
      w, h); /// image 
    } 
} 

而且你應該叫DrawLevel1在這裏：

function Draw() { 
    ctx.clearRect(0, 0, cw, ch); 
    DrawLevel1(); // here 
    PlayerTank.draw(); 
    Missiles.draw(); 
    Enemies.draw(); 
}