如何使它在PNG上悬停透明不算盘旋？ [英] How to make it so that Hovering Over Transparency in a PNG doesn't count as hovering?

问题描述

当我将鼠标悬停在PNG的透明部分上时，它仍然像我在实际图像上悬停一样。有没有办法可以防止这种情况发生？所以当我将鼠标悬停在图像的可见部分而不是透明部分时，它只会采取行动？我试图突出显示透明度，但我不能'

解决方案

可以通过将png转换为canvas元素来完成

这可以通过将png加载到HTML-5 canvas元素中，然后查询画布中被点击的像素的alpha值来实现。

工作演示： http://jsfiddle.net/x9ScK/3/

HTML如下...

 <！ - 创建一个画布元素来容纳PNG图像 - > 
< canvas id =canvas1width =500height =500>< / canvas> 
  

Javascript like this ...

 //用jQuery选择canvas元素，并设置
 //为整个画布单击处理程序
 $（'＃canvas1'）。on（'click '，函数（e）{
 //用于查找单击像素位置的实用函数
函数findPos（obj）{
 var curleft = 0，curtop = 0; 
如果（obj.offsetParent）{
做{
 curleft + = obj.offsetLeft; 
 curtop + = obj.offsetTop; 
}，而（OBJ = obj.offsetParent）; 
 return {x：curleft，y：curtop}; 
} 
 return undefined; 
} 
 //获得点击像素的位置
 var pos = findPos（this）; 
 var x = e.pageX  -  pos.x; 
 var y = e.pageY  -  pos.y; 
 //获取单击$ b上的canvas元素的引用$ b var canvas = this.getContext（'2d'）; 
 //返回[RED，GREEN，BLUE，ALPHA]数组作为点击像素的0-255 
 var pixel = canvas.getImageData（x，y，1，1）.data; 
 //如果alpha不是0，我们点击一​​个不透明的像素
 //可以很容易地调整以检测点击像素的其他特征
 if（pixel [3]！= 0）{
 //点击图片时做点什么... 
 alert（点击骰子！）; 
} 
}）; 
 
 //获取对画布DOM元素的引用
 var canvas = $（'＃canvas1'）[0]; 
 //获得对canvas上下文的引用
 var context = canvas.getContext（'2d'）; 
 
 //创建一个空的图像
 var img = new Image（）; 
 //加载后... 
 img.onload = function（）{
 //将图像绘制到画布上
 context.drawImage（img，0，0）; 
} 
 
 //设置图片来源（可以是任何网址 - 我使用数据URI来保持演示不变）
 img.src =data：image / png; base64，iVBORw0KGgoAAAANS ...更多图片数据... TkSuQmCC; //带透明度的PNG 
  

When I hover over the transparent part of a PNG, it still acts as though I'm hovering over the actual image. Is there a way that I can prevent that from happening? So that it only takes action when I hover over the visible part of the image, and not the transparent part?

I tried to crop out the transparency, but I couldn't find a way how.

解决方案

Can be done by converting png to canvas element

This works by loading a png into an HTML-5 canvas element, and then querying the canvas for the alpha value of the clicked pixel.

Working demo: http://jsfiddle.net/x9ScK/3/

HTML as follows...

<!-- create a canvas element to hold the PNG image -->
<canvas id="canvas1" width="500" height="500"></canvas>

Javascript like this...

// select the canvas element with jQuery, and set up
// a click handler for the whole canvas
$('#canvas1').on('click', function(e) {
    // utility function for finding the position of the clicked pixel
    function findPos(obj) {
        var curleft = 0, curtop = 0;
        if (obj.offsetParent) {
            do {
                curleft += obj.offsetLeft;
                curtop += obj.offsetTop;
            } while (obj = obj.offsetParent);
            return { x: curleft, y: curtop };
        }
        return undefined;
    }
    // get the position of clicked pixel
    var pos = findPos(this);
    var x = e.pageX - pos.x;
    var y = e.pageY - pos.y;
    // get reference to canvas element clicked on
    var canvas = this.getContext('2d');
    // return array of [RED,GREEN,BLUE,ALPHA] as 0-255 of clicked pixel
    var pixel = canvas.getImageData(x, y, 1, 1).data;
    // if the alpha is not 0, we clicked a non-transparent pixel
    // could be easily adjusted to detect other features of the clicked pixel
    if(pixel[3] != 0){
        // do something when clicking on image...
        alert("Clicked the dice!");
    }
});

// get reference to canvas DOM element
var canvas = $('#canvas1')[0];
// get reference to canvas context
var context = canvas.getContext('2d');

// create an empty image
var img = new Image();
// after loading...
img.onload = function() {
    // draw the image onto the canvas
    context.drawImage(img, 0, 0);
}

// set the image source (can be any url - I used data URI to keep demo self contained)
img.src = "data:image/png;base64,iVBORw0KGgoAAAANS ... more image data ...TkSuQmCC"; // PNG with transparency

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