1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
2 <html>
3 <head>
4 <title>CSS Test: blur computation for box-shadow</title>
5 <link rel="author" title="L. David Baron" href="https://dbaron.org/">
6 <link rel="author" title="Mozilla Corporation" href="http://mozilla.com/">
7 <link rel="help" href="http://www.w3.org/TR/css3-background/#the-box-shadow">
8 <meta name="flags" content="">
9 <meta name="assert" content="the resulting shadow must approximate (with each pixel being within 5% of its expected value) the image that would be generated by applying to the shadow a Gaussian blur with a standard deviation equal to half the blur radius">
10 <style type="text/css">
11 div.stripecontainer {
12 width: 600px;
13 height: 30px;
14 border: medium solid blue;
15 }
16 div.refimage, div.blurcontainer {
17 width: 600px;
18 height: 10px;
19 }
20 div.refimage img {
21 display: block;
22 }
23 div.blurcontainer { position: relative; overflow: hidden }
24 div.blur {
25 position: absolute;
26 width: 2000px;
27 height: 2010px;
28 top: -1000px; /* places 1000px both above and below container */
29 left: -2000px; /* places right edge at left of container */
30 box-shadow: 300px 0 100px black;
31 }
32 </style>
33 </head>
34 <body>
35 <p>The following test should contain three grayscale stripes, each 10
36 pixels tall, with no space between them, but all enclosed within a
37 blue border. At all points, the middle stripe must be <strong>the
38 same color as or darker than</strong> the top stripe, and <strong>the
39 same color as or lighter than</strong> the bottom stripe. (This tests
40 that the blurring algorithm produces results within 5% of a Gaussian
41 blur.)</p>
42 <div class="stripecontainer">
43 <div class="refimage"><img height="10" width="600" src="support/box-shadow-blur-definition-001-light-bound.png" alt="[reference stripe image]"></div>
44 <div class="blurcontainer"><div class="blur"></div></div>
45 <div class="refimage"><img height="10" width="600" src="support/box-shadow-blur-definition-001-dark-bound.png" alt="[reference stripe image]"></div>
46 </div>
47 </body>
48 </html>