Question

我正在使用HTML5和javascript进行项目。我有一个画布将在哪个文档上加载。

canvas = document.getElementById('pdf');
ctx = canvas.getContext('2d');

在上面的画布中，将加载文档。我必须在运行时在其上绘制不同的形状作为单独的画布。所以在绘图时我必须为每个Shape（必需）创建一个新画布。

的MouseDown

function mouse_Pressed(e) {
     getMouse(e);//getting current X and Y position
 x1=mx; y1=my;
    var cords=getMousePos(canvas,e); 
    annCanvas=document.createElement('canvas'); //Creating 
    annCanvasContext=annCanvas.getContext('2d');
     isDraw=true;isDrawAnn=true;
}

的MouseMove

function mouse_Dragged(e)
{
    if(isDraw)
    {
    getMouse(e);
    x2=mx; y2=my;
    calculatePoints(x1,y1,x2,y2);
    var width=endX-startX;
    var height=endY-startY;
    annCanvas.style.position = "absolute";
    annCanvas.width=4; //Width of square
    annCanvas.style.left=""+startX+"px";
    annCanvas.style.top=""+startY+"px";
    annCanvas.height=height;
    annCanvas.style.zIndex="100000";

    document.getElementById("canvas").appendChild(annCanvas);
    annCanvasContext.fillStyle='rgb(255,255,0)';
    annCanvasContext.lineWidth=borderWidth;
    annCanvasContext.strokeRect(0,0,width,height);
    annCanvasContext.stroke();
 }
}

的mouseReleased

function mouse_Released(e)
{
 isDrag = false;
 isDraw=false;
 isDrawAnn=false;
}

主要问题是，如果我绘制边框宽度为50的矩形，那么其Canvas外部部分将因为较少的画布区域（即矩形）而切割。所以我想用borderWidth计算画布高度，宽度。

Answer 1

这应考虑边框宽度和宽度等。

function init() {
    var canvas = document.getElementById("canvas");
    var ctx = canvas.getContext("2d");
    var s = size(canvas);
    alert(s[0]);
}


function size(el) {
    var clientHeight = (el.offsetHeight > el.clientHeight) ? el.offsetHeight : el.clientHeight;
    var clientWidth = (el.offsetWidth > el.clientWidth) ? el.offsetWidth : el.clientWidth;
    return [clientWidth, clientHeight];
};

HTML：

<body onload="init();">
<canvas id="canvas" width="200" height="300" style="width: 500px; height: 400px; border: 10px solid brown;"></canvas>
</body>

如何计算形状高度和宽度，包括画布中的边框宽度？

1 个答案: