Overlay HTML5 canvas over image

问题

I want to have an image which is uploaded from my database and on top of it the exact same size in the same position is a HTML5 canvas.

Most of the solutions I have found I have been using JQuery/JavaScript, however I want a similar solution if possible just using CSS3 as the images are being outputted from a database and there can be more than one image on the page and each image will have a canvas.

How can I achieve this?

回答1:

Yes.

You can do this entirely in CSS, but you will have to add some specific HTML plumbing for each image.

If you ever get tired of the extra plumbing, javascript could do most of the plumbing for you.

Here is a Fiddle of the CSS-only version:

http://jsfiddle.net/m1erickson/g3sTL/

The HTML:

<div class="outsideWrapper">
    <div class="insideWrapper">
        <img src="house-icon.jpg" class="coveredImage">
        <canvas class="coveringCanvas"></canvas>
    </div>
</div>

Of course, in your version, you would replace the image src with your dynamic database call to fetch the image.

The CSS:

.outsideWrapper{ 
    width:256px; height:256px; 
    margin:20px 60px; 
    border:1px solid blue;}
.insideWrapper{ 
    width:100%; height:100%; 
    position:relative;}
.coveredImage{ 
    width:100%; height:100%; 
    position:absolute; top:0px; left:0px;
}
.coveringCanvas{ 
    width:100%; height:100%; 
    position:absolute; top:0px; left:0px;
    background-color: rgba(255,0,0,.1);
}

回答2:

Possible duplicate.

Depending on how many images are in the database, you could have a separate canvas id for each with the name of the image file (e.g. canvas #foo { background:url(foo.jpg) }). I would load this in a separate stylesheet. :)

It would probably be easier to maintain a Javascript solution though if your database is dynamic. A few lines of javascript would be sufficient, instead of constantly updating a stylesheet with new names. Less ~~error~~ typo prone as well.

来源：https://stackoverflow.com/questions/14824747/overlay-html5-canvas-over-image

标签

html

css

html5-canvas