如何使用画布修改来自另一个域的图像?
这是我使用 image.src = "/local/directory/image.png" 时使用的代码，但如果我使用 image.src="http://remote/path" 它会加载图像，但其余的 mousemove 功能不起作用.你是怎么解决的?
This is the code i am using when i have image.src = "/local/directory/image.png" works but if i use image.src="http://remote/path" it loads the image but rest mousemove function do not work. How do you fix it?
复制粘贴到 test.htm
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<script>
$(document).ready(function()
{
var image = new Image();
var ctx = $('#canvas')[0].getContext("2d");
image.src = "http://www.google.com/intl/en_com/images/srpr/logo3w.png";
//image.src = "/agents/google.png";
image.width="340";
image.height="220";
image.onload = function ()
{
ctx.drawImage(image, 0, 0, image.width, image.height);
}
$('#canvas').mousemove(function(e)
{
var canvasOffset = $(this).offset();
var canvasX = Math.floor(e.pageX - canvasOffset.left);
var canvasY = Math.floor(e.pageY - canvasOffset.top);
var imageData = ctx.getImageData(canvasX, canvasY, 1, 1);
var pixel = imageData.data;
var pixelColor = "rgba("+pixel[0]+", "+pixel[1]+", "+pixel[2]+", "+pixel[3]+")";
$(document.body).css('background-color',pixelColor);
});
});
</script>
<body>
<canvas id="canvas" width="340" height="220"></canvas>
<body>
跟进(复制粘贴):
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<script type="text/javascript" src="https://raw.github.com/betamax/getImageData/master/jquery.getimagedata.min.js"></script>
<script>
$(document).ready(function()
{
// var image = new Image();
// var ctx = $('#canvas')[0].getContext("2d");
// //image.src = "http://www.google.com/intl/en_com/images/srpr/logo3w.png";
// image.src = "/agents/google.png";
//
// image.width="340";
// image.height="220";
// image.onload = function ()
// {
// ctx.drawImage(image, 0, 0, image.width, image.height);
// }
// $('#canvas').mousemove(function(e)
// {
// var canvasOffset = $(this).offset();
// var canvasX = Math.floor(e.pageX - canvasOffset.left);
// var canvasY = Math.floor(e.pageY - canvasOffset.top);
// var imageData = ctx.getImageData(canvasX, canvasY, 1, 1);
// var pixel = imageData.data;
//
// var pixelColor = "rgba("+pixel[0]+", "+pixel[1]+", "+pixel[2]+", "+pixel[3]+")";
// $(document.body).css('background-color',pixelColor);
//
// });
$.getImageData({
url: "http://www.google.com/intl/en_com/images/srpr/logo3w.png",
success: function(image){
// Set up the canvas
var can = document.getElementsByTagName('canvas')[0];
var ctx = can.getContext('2d');
// Set the canvas width and heigh to the same as the image
$(can).attr('width', image.width);
$(can).attr('height', image.height);
// Draw the image on to the canvas
ctx.drawImage(image, 0, 0, image.width, image.height);
// Get the image data
var image_data = ctx.getImageData(0, 0, image.width, image.height);
var image_data_array = image_data.data;
// Invert every pixel
//for (var i = 0, j = image_data_array.length; i < j; i+=4) {
//image_data_array[i] = 255 - image_data_array[i];
//image_data_array[i+1] = 255 - image_data_array[i+1];
//image_data_array[i+2] = 255 - image_data_array[i+2];
//}
// Write the image data to the canvas
ctx.putImageData(image_data, 0, 0);
$('#canvas').mousemove(function(e)
{
var canvasOffset = $(this).offset();
var canvasX = Math.floor(e.pageX - canvasOffset.left);
var canvasY = Math.floor(e.pageY - canvasOffset.top);
var imageData = ctx.getImageData(canvasX, canvasY, 1, 1);
var pixel = imageData.data;
var pixelColor = "rgba("+pixel[0]+", "+pixel[1]+", "+pixel[2]+", "+pixel[3]+")";
$(document.body).css('background-color',pixelColor);
});
},
error: function(xhr, text_status){
// Handle your error here
}
});
});
</script>
<body>
<canvas id="canvas" width="340" height="220"></canvas>
<body>
推荐答案
无法直接从其他域读取图像.
It's not possible to directly read an image from another domain.
但是，操作来自另一个域的图像可以通过获取图像的 base-64 字符串解释并使用它来实现.
However, manipulate images from another domain can be achieved by getting a base-64 string interpretation of the image, and use it.
这个功能是由 $.imagedata 插件在 jQuery 中实现的，可以在 此网站.
This feature is implemented in jQuery by the $.imagedata plugin, which can be downloaded at this site.
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