与画布矩形交互 [英] Interacting with Canvas Rectangle

问题描述

我的简单 HTML 页面中有一个 canvas 元素，它使用 context.fillRect() 方法绘制了几个矩形.我需要与这些绘制的矩形进行交互.

I have a canvas Element in my simple HTML page and it has few rectangles drawn using context.fillRect() method. I need to interact with these drawn rectangles.

我该怎么做?如何将 onclick 或 onmouseover 与这些矩形绑定?

How can I do so? How can I bind onclick or onmouseover with these rectangles?

推荐答案

您需要跟踪坐标并检查鼠标是否在如下矩形之一中:http://jsfiddle.net/eGjak/13/.

You'd need to keep track of the coordinates and check whether the mouse is in one of the rectangles like this: http://jsfiddle.net/eGjak/13/.

显然，您也可以使用 mouseover 代替 click.

Obviously, instead of click you could also use mouseover.

var ctx = $('#cv').get(0).getContext('2d');

var rects = [[0, 0, 100, 100], [0, 150, 50, 100]]; // [x, y, width, height]
for(var i=0;i<rects.length;i++) {
    ctx.fillRect(rects[i][0], // fill at (x, y) with (width, height)
                 rects[i][1],
                 rects[i][2],
                 rects[i][3]);
}

$('#cv').click(function(e) {
    var x = e.offsetX,
        y = e.offsetY;

    for(var i=0;i<rects.length;i++) { // check whether:
        if(x > rects[i][0]            // mouse x between x and x + width
        && x < rects[i][0] + rects[i][2]
        && y > rects[i][1]            // mouse y between y and y + height
        && y < rects[i][1] + rects[i][3]) {
            alert('Rectangle ' + i + ' clicked');
        }
    }
});

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