Mozilla的getImageDataProblem

Question

我在Mozilla的getImageData有問題。我做了一個函數，點擊畫布後獲取鼠標的座標。座標是好的，但是有一個問題，在Mozilla中，它給出了很多糟糕的getImageDatas數字 - 例如在chrome中，它給出了紅色：10，綠色：0，藍色：10，Mozilla給出紅色：60，綠色：255，藍色：10 ...我不知道問題出在哪裏......請你幫忙嗎？ 下面是函數：http://pastebin.com/MjnG0Nbm

Answer 1

也許你getMousePos（）並不總是得到希望的結果

The amount of scrolling that has been done of the viewport area (or any other 
scrollable element) is taken into account when computing the bounding rectangle. 
This means that the top and left property change their values as soon as the 
scrolling position changes (so their values are relative to the viewport and not 
absolute). If this is not the desired behaviour just add the current scrolling 
position to the top and left property (via window.scrollX and window.scrollY) to 
get constant values independent from the current scrolling position. 

試試這個：

function getMousePosition(canvas, evt) { 
    return { 
     x: evt.clientX - canvas.offsetLeft + window.scrollX, 
     y: evt.clientY - canvas.offsetTop + window.scrollY 
    };   
}