In browser can I get the image color where my mouse is pointing at?_问答_开发者

In browser can I get the image color where my mouse is pointing at?

开发者 https://www.devze.com 2022-12-22 11:33 出处：网络

There is a web application for me to build, and rather than image map, I would like to try something more elegant.

The story is, there gonna be a global map where different continents are denoted by different colors.

Say Australia is red and Asia is green.

Will there be a way that when my mouse is hovering on the shape of Australia that my code will tell me that I am hovering on Australia by checking for the color where my cursor is currently pointing at?

I know I can check for mouse coordinates on image or something else, but I really want to get something that is not depending on pre-defined values/sh开发者_JS百科apes/margins.

Any idea and suggestion would be much appreciated. Thanks a lot in advance.

It depends on what kind of element your map is. It is definitely possible for certain elements in browsers that support canvas, but not for the whole page.

See the answers to my similar question: JavaScript eyedropper (tell colour of Pixel under mouse cursor)

Merging various references found here in StackOverflow and in other sites, I did so using javascript and JQuery:

<html>
<body>
<canvas id="myCanvas" width="400" height="400" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
</canvas>
<script src="jquery.js"></script>
<script type="text/javascript">
    window.onload = function(){
        var canvas = document.getElementById('myCanvas');
        var context = canvas.getContext('2d');
        var img = new Image();
        img.src = 'photo_apple.jpg';
        context.drawImage(img, 0, 0);
    };

    function findPos(obj){
    var current_left = 0, current_top = 0;
    if (obj.offsetParent){
        do{
            current_left += obj.offsetLeft;
            current_top += obj.offsetTop;
        }while(obj = obj.offsetParent);
        return {x: current_left, y: current_top};
    }
    return undefined;
    }

    function rgbToHex(r, g, b){
    if (r > 255 || g > 255 || b > 255)
        throw "Invalid color component";
    return ((r << 16) | (g << 8) | b).toString(16);
    }

$('#myCanvas').click(function(e){
    var position = findPos(this);
    var x = e.pageX - position.x;
    var y = e.pageY - position.y;
    var coordinate = "x=" + x + ", y=" + y;
    var canvas = this.getContext('2d');
    var p = canvas.getImageData(x, y, 1, 1).data;
    var hex = "#" + ("000000" + rgbToHex(p[0], p[1], p[2])).slice(-6);
    alert("HEX: " + hex);
});
</script>
<img src="photo_apple.jpg"/>
</body>
</html>

Here I only used canvas and one image, but if you need to use <map> over the image, it's possible too. I hope I have helped!