我正在使用canvas，现在我可以保存到DB中，我可以将背景图像更改为我选择的图像列表。
我的问题是，当我尝试使用背景保存画布时，保存的图像只显示绘制但不显示图像背景...有人可以帮我这个吗？
最诚挚的问候！
这里是代码：
[[4 1 0 0]
[4 0 2 0]
[0 3 0 0]
[0 2 0 0]
[4 0 0 0]]
这里带有图片的表格：
<script src="js/drawingboard.min.js"></script>
<script data-example="1">
var defaultBoard = new DrawingBoard.Board("default-board", {
background: "#ffff",
droppable: true,
webStorage: false,
enlargeYourContainer: true,
addToBoard: true,
stretchImg: false
});
defaultBoard.addControl("Download");
$(".drawing-form").on("submit", function(e) {
var img = defaultBoard.getImg();
var imgInput = (defaultBoard.blankCanvas == img) ? "" : img;
$(this).find("input[name=image]").val( imgInput );
defaultBoard.clearWebStorage();
});
$(function() {
$("#file-input").change(function(e) {
var file = e.target.files[0],
imageType = /image.*/;
if (!file.type.match(imageType))
return;
var reader = new FileReader();
reader.onload = fileOnload;
reader.readAsDataURL(file);
});
function fileOnload(e) {
var $img = $("<img>", { src: e.target.result });
var canvas = $("#default-board")[0];
var context = canvas.getContext("2d");
$img.load(function() {
context.drawImage(this, 0, 0);
});
}
});
</script>
<script src="js/yepnope.js"></script>
<script>
var iHasRangeInput = function() {
var inputElem = document.createElement("input"),
smile = ":)",
docElement = document.documentElement,
inputElemType = "range",
available;
inputElem.setAttribute("type", inputElemType);
available = inputElem.type !== "text";
inputElem.value = smile;
inputElem.style.cssText = "position:absolute;visibility:hidden;";
if ( /^range$/.test(inputElemType) && inputElem.style.WebkitAppearance !== undefined ) {
docElement.appendChild(inputElem);
defaultView = document.defaultView;
available = defaultView.getComputedStyle &&
defaultView.getComputedStyle(inputElem, null).WebkitAppearance !== "textfield" &&
(inputElem.offsetHeight !== 0);
docElement.removeChild(inputElem);
}
return !!available;
};
yepnope({
test : iHasRangeInput(),
nope : ["css/fd-slider.min.css", "js/fd-slider.min.js"],
callback: function(id, testResult) {
if("fdSlider" in window && typeof (fdSlider.onDomReady) != "undefined") {
try { fdSlider.onDomReady(); } catch(err) {}
}
}
});
// with this code I can change the background
$(document).ready(function () {
$("#cambiocanvas > input").click(function () {
var img = $(this).attr("src");
$(".drawing-board-canvas").css("background", "url(" + img + ")");
});
});
</script>
CODE EDITED
这里是代码：
<div class="tab-pane" id="derm">
<div class="row-fluid sortable">
<div class="box span3">
<section id="cambiocanvas">
<input id="yellowcanvas" class="canvasborder" type="image" src="http://2.imimg.com/data2/MB/BH/MY-651900/23-250x250.jpg">
<input id="bluecanvas" class="canvasborder" type="image" src="http://jsfiddle.net/img/logo.png">
<input id="greencanvas" class="canvasborder" type="image" src="https://www.gravatar.com/avatar/86364f16634c5ecbb25bea33dd9819da?s=128&d=identicon&r=PG&f=1">
</section>
</div>
<div class="box span9">
<div class="box-header well" data-original-title>
<h2><i class="icon-tasks"></i> </h2>
<div class="box-icon">
<a href="#" class="btn btn-minimize btn-round"><i class="icon-chevron-up"></i></a>
<a href="#" class="btn btn-close btn-round"><i class="icon-remove"></i></a>
</div>
</div>
<div class="box-content">
<div id="container">
<div class="example" data-example="1">
<div class="board" id="default-board"></div>
</div>
<form class="drawing-form" method="post" name="diagram" id="diagram" enctype="multipart/form-data">
<div id="board"></div>
<input type="hidden" name="image" value="">
<input type="hidden" name="id_user" value="<?php echo $id" />
<br><hr>
<button class="btn btn-info" id="btnUpload">Save</button>
</form>
<div id="ldiag" style="display:none;"><img src="images/loading4.gif" /></div>
<div class="progress1"></div>
<div id="diaga"></div>
</div>
</div>
</div>
答案 0 :(得分：5)
画布元素的背景（图像）不是画布内容的一部分，因此不会保存。
解决方法，如果你不能重绘画布
如果你想在使用复合操作“destination-over”保存之前将背景渲染到画布上，它只会添加画布透明或半透明的像素，你会看到元素背景。
ctx.globalCompositeOperation = "destination-over";
ctx.drawImage(backgroundImage,0,0);
ctx.globalCompositeOperation = "source-over"; // restore default
加载画布CSS背景图片
var background = new Image;
background.src = canvas.style.background.replace(/url\(/|\)/gi,"").trim();
// wait till it has loaded.
您可能需要拉伸图像
ctx.drawImage(background,0,0,ctx.canvas.width,ctx.canvas.height);
替代解决方案使用屏幕外画布并首先绘制背景，然后绘制原始画布。
// ensure that the image has loaded before running this code.
// canvas is the original canvas that you want to add the background to
// ctx is the origin canvas context
var can2 = document.createElement("canvas");
can2.width = canvas.width;
can2.height = canvas.height;
var ctx2 = can2.getContext("2d");
ctx2.drawImage(background,0,0,ctx.canvas.width,ctx.canvas.height);
ctx2.drawImage(canvas,0,0);
// put the new result back in the original canvas so you can save it without changing code.
ctx.clearRect(0,0,ctx.canvas.width,ctx.canvas.height);
ctx.drawImage(can2,0,0);
或者提供复制和粘贴解决方案
function fileOnload(e) {
var canvas = $("#default-board")[0];
var context = canvas.getContext("2d");
var background = new Image;
background.src = canvas.style.background.replace(/url\(|\)/gi,"").trim();
background.onload = function(){
var $img = $("<img>", { src: e.target.result });
$img.load(function() {
context.drawImage(backgroundImage, 0, 0, canvas.width, canvas.height);
context.drawImage(this, 0, 0);
});
}
});
答案 1 :(得分：0)
你快完成了。请尝试更改此代码：
$(document).ready(function () {
$("#cambiocanvas > input").click(function () {
var img = $(this).attr("src");
$("#default-board").css("background", "url(" + img + ")");
});
});
对此：
$(".canvasborder").click(function(){
var src = $(this).attr("src");
defaultBoard.setImg(src);
});
像这样：
var defaultBoard = new DrawingBoard.Board("default-board", {
background: "#fff",
droppable: true,
webStorage: false,
enlargeYourContainer: true,
addToBoard: true,
stretchImg: true
});
defaultBoard.addControl("Download");
$(".canvasborder").click(function(){
var src = $(this).attr("src");
defaultBoard.setImg(src);
});
$(".drawing-form").on("submit", function(e) {
var img = defaultBoard.getImg();
var imgInput = (defaultBoard.blankCanvas == img) ? "" : img;
$(this).find("input[name=image]").val( imgInput );
defaultBoard.clearWebStorage();
});
$(function() {
$("#file-input").change(function(e) {
var file = e.target.files[0],
imageType = /image.*/;
if (!file.type.match(imageType))
return;
var reader = new FileReader();
reader.onload = fileOnload;
reader.readAsDataURL(file);
});
function fileOnload(e) {
var canvas = $("#default-board")[0];
var context = canvas.getContext("2d");
var background = new Image;
background.src = canvas.style.background.replace(/url\(|\)/gi,"").trim();
background.onload = function(){
var $img = $("<img>", { src: e.target.result });
$img.load(function() {
context.drawImage(backgroundImage, 0, 0, canvas.width, canvas.height);
context.drawImage(this, 0, 0);
});
}
}
});
并且可以处理您在选择列表中放置的任何图像，请记住它必须附带Access-Control-Allow-Origin标题，以允许页面的来源（可能通过*通配符）。< / p>