发表新帖
发表新帖

drawing images on 3 layer canvas and saving

后端 未结
关注
1 1271
闹比i
闹比i 2021-01-07 11:43

I have a 3 layers of canvas, which I have given a separate id to each.

This is what I am doing.

HTML



        

                      

              相关标签:
1条回答
  • 半阙折子戏
    2021-01-07 12:22

    To draw on all three “layers” you must create contexts for all layers

    // references to layer1
var canvas1 = document.getElementById('layer1');
var context1 = canvas1.getContext('2d');

// references to layer2
var canvas2 = document.getElementById('layer2');
var context2 = canvas2.getContext('2d');

// references to layer3
var canvas3 = document.getElementById('layer3');
var context3 = canvas3.getContext('2d');

    Then after you’re done drawing on all layers, merge them (here merged onto layer1):

    // merge all layers onto layer1
context1.drawImage(canvas2,0,0);
context1.drawImage(canvas3,0,0);

    And finally save the merged canvas to an image and set your img src to that image.

    // save the merged drawings as an image
// and set the img element src to that merged image
var img=new Image();
img.onload=function(){
    document.getElementById("results").src=img.src;
}
img.src=canvas1.toDataURL();

    Here is code and a Fiddle: http://jsfiddle.net/m1erickson/fhjwY/

    <!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>

<style>
    body{ background-color: ivory; }
    canvas{border:1px solid red;}
</style>

<script>
$(function(){

// references to layer1
var canvas1 = document.getElementById('layer1');
var context1 = canvas1.getContext('2d');

// references to layer2
var canvas2 = document.getElementById('layer2');
var context2 = canvas2.getContext('2d');

// references to layer3
var canvas3 = document.getElementById('layer3');
var context3 = canvas3.getContext('2d');

// draw stuff on the layers
context1.fillStyle="red";
context2.fillStyle="blue";
context3.fillStyle="green";

context1.fillRect(20,20,50,50);
context2.fillRect(50,50,50,50);
context3.fillRect(80,80,50,50);

// merge all layers onto layer1
context1.drawImage(canvas2,0,0);
context1.drawImage(canvas3,0,0);

// save the merged drawings as an image
// and set the img element src to that merged image
var img=new Image();
img.onload=function(){
    document.getElementById("results").src=img.src;
}
img.src=canvas1.toDataURL();



}); // end $(function(){});
</script>

</head>

<body>
    <p>Draw rects on 3 canvases</p>
    <p>Merge all drawings to 1st canvas</p>
    <p>Create an image from merged drawings</p>
    <p>Set the image element with that merged image</p>
    <canvas id="layer1" width=150 height=150></canvas>
    <canvas id="layer2" width=150 height=150></canvas><br>
    <canvas id="layer3" width=150 height=150></canvas>
    <img id="results" width=150 height=150>
</body>
</html>
    0 讨论(0)
 看不清?
提交回复
热议问题