Tag / Html

by Aaron

How to mask an image in HTML/CSS

Until browsers all agree on a technique for masking an image in HTML (like –web-kit-mask-image), I’ve got another option: using SVG.

image

I’m creating a single page application to help sell some electronics and other goodies I’ve collected over the years. Rather than the traditional rectangular display of photos, I wanted to try something different. I wanted the photos to be round. However, I didn’t want to create a bunch of round images.

Enter SVG:

<svg width="220" height="220">
                    <mask id="m1"><ellipse cx="110" cy="110" rx="98" ry="98" style="fill:white;stroke-width:0;fill-opacity: 1.0"></ellipse></mask>
                    <g>
                        <ellipse cx="110" cy="110" rx="100" ry="100" style="stroke-width:10;stroke:#222"></ellipse>
                        <image href="img/sales/lenovo/IMG_0468.jpg" x="-25%" y="-25%" height="150%" width="150%" style="mask: url(#m1)"></image></g></svg>

The original images aren’t square, so I tweaked the size and position of each so that it would completely fill the ellipse (150% and -25% for size and location).  As a fall back, I’m going to add the CSS property and value “display:none” to a standard HTML img element that will be optionally displayed if the browser can’t do SVG (like IE8 and lower for example). I don’t want to lose a potential sale to images not showing up! I’ll use modernizr for SVG detection.

And although the code above doesn’t demonstrate the technique, you can use CSS to decorate the SVG. Check this demo out that I created:

image

image

image

by Aaron

SVG Setting Text Content Dynamically

Continuing on a theme of animating SVG, I’ve added a label in the center of the animation which contains the current angle of the ever-rotating marker (in fact in a centered horizontally and vertically SVG text node).

(Click image below to try it.)

image

At the bottom of the file from the previous post, I’ve added the following: 

    <text id="currentValueAsText" x="300" y="300" 
        style="text-anchor: middle;alignment-baseline:middle" 
        fill="#FFFFFF" font-family="'Arial'" font-size="96" opacity=".6">0</text>

It’s a new text node. It’s set to centered both horizontally and vertically (using the text-anchor and alignment-baseline style properties respectively) at 300,300.

Setting the content is simple as well:

(function () {
    window.onload = loaded;
    function loaded() {
        var colorTemp = document.getElementById("color-temp");
        var reading = document.getElementById('current-reading');
        var currentVal = document.getElementById("currentValueAsText");
        var currentAngle = 0;
        var fill;

        var direction = 1;
        setInterval(function () {
            currentAngle += direction;
            if (currentAngle >= 120 || currentAngle <= -120) {
                direction *= -1;
            } else if (currentAngle === 0) {
                fill = direction === 1 ? "#BE1E2D" : "#10A2DC";
                colorTemp.setAttribute("fill", fill);
            }
            // adjust the opacity
            colorTemp.setAttribute("opacity", Math.abs(currentAngle) / 120.0);
            reading.setAttribute("transform", "rotate(" + currentAngle + ")");
            currentValueAsText.textContent = currentAngle.toString();

        }, 25);
    }
})();

Use the textContent property of the SVG text node to set the text.

Done. Smile

by Aaron

Spinning SVG Animation

Interested in learning a few capabilities of SVG animation this evening from JavaScript in a web page, I put together a simple demonstration.

Click on the image to launch the demo.

image

Animating SVG in a modern browser (including IE9) is generally easy enough. This example was slightly more interesting in that I wanted the thicker line to rotate based on the center point of the image, rather than the location of the line itself.

Not what I wanted:

image

Desired rotation:

image

The white bar would rotate around the center point (marked by the red arrow above).

I’ve included all of the code at the bottom of the post. (There’s quite a lot of path information).

The JavaScript just used an interval to move the line around the point:

(function () {
    window.onload = loaded;
    function loaded() {
        var colorTemp = document.getElementById("color-temp");
        var reading = document.getElementById('current-reading');
        var currentAngle = 0;
        var fill;

        var direction = 1;
        setInterval(function () {
            currentAngle += direction;
            if (currentAngle >= 120 || currentAngle <= -120) {
                direction *= -1;
            } else if (currentAngle === 0) {
                fill = direction === 1 ? "#BE1E2D" : "#10A2DC";
                colorTemp.setAttribute("fill", fill);
            }
            // adjust the opacity
            colorTemp.setAttribute("opacity", Math.abs(currentAngle) / 120.0);

            reading.setAttribute("transform", "rotate(" + currentAngle + ")");

        }, 25);
    }
})();

The angle is fixed between 120 and –120 degrees. When the angle reaches zero, the fill color is toggled.

As the angle adjusts, the line is updated as well as the opacity of the fill.

The overall size of the SVG drawing is 600×600. Knowing that (and wanting the exact center), I translated a group to an offset of 300x, 300y containing the line: 

<g id="temp-transform" transform="translate(300,300)">
        <line id="current-reading" fill="none" stroke="#FFFFFF"
              stroke-width="5" stroke-linecap="round"
              stroke-miterlimit="10" x1="0" y1="-180" x2="0" y2="-120"/>
</g>

This effectively made the rotation now work from the center, once the line coordinates were adjusted to reflect the new translation.

This works because the contents of the outer group caused the new starting point (origin) to be 300x, 300y rather than the default 0x, 0y. You can see the line is from y –120 to y –180. That’s because I wanted the line to start in the top middle (as the x is set to 0 for the line).

I used Adobe Illustrator CS 5.5 to create the SVG image. Illustrator typically does not always handle fonts well when exporting as SVG. The final text node was this: 

<text transform="matrix(1 0 0 1 254.1387 83.3198)" fill="#D1D3D4" font-family="'Arial'"
      font-weight="bold" font-size="29.4616">thermo</text>

To make it work across browsers, I needed to modify the text node below slightly. Note the font name and missing bold attribute. It’s not a hard switch, but it’s annoying if you need to make changes to your SVG multiple times. 

<text transform="matrix(1 0 0 1 254.1387 83.3198)" fill="#D1D3D4" 
font-family="'Arial-BoldMT'" font-size="29.4616">thermo</text>

If you have any questions, please leave a comment!

<!DOCTYPE HTML>
<html>
<head>
    <title>Svg Spinner Demo</title>
    <style>
        #demo1 svg {
            width: 300px;
            height: 300px;
        }

    </style>
</head>
<body>

<div id="demo1">
<svg version="1.0" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
     width="600px" height="600px" viewBox="0 0 600 600" enable-background="new 0 0 600 600" xml:space="preserve">
<g>
    <radialGradient id="SVGID_1_" cx="298.9106" cy="196.146" r="399.267" gradientUnits="userSpaceOnUse">
        <stop  offset="0" style="stop-color:#D9D9D9"/>
        <stop  offset="1" style="stop-color:#C2C2C2"/>
    </radialGradient>
    <path fill="url(#SVGID_1_)" d="M300.646,595.41c-78.957,0-153.188-30.747-209.02-86.579C35.795,453,5.048,378.77,5.048,299.812
        c0-78.957,30.748-153.188,86.579-209.02S221.689,4.214,300.646,4.214c78.958,0,153.188,30.748,209.019,86.579
        c55.832,55.831,86.579,130.063,86.579,209.02c0,78.958-30.747,153.188-86.579,209.019
        C453.834,564.663,379.604,595.41,300.646,595.41z"/>
    <path fill="#808285" d="M300.646,6.214c39.637,0,78.086,7.762,114.281,23.071c34.961,14.787,66.359,35.957,93.324,62.922
        s48.135,58.364,62.923,93.325c15.309,36.193,23.07,74.643,23.07,114.28s-7.762,78.086-23.07,114.281
        c-14.788,34.961-35.958,66.359-62.923,93.324s-58.363,48.135-93.324,62.923c-36.194,15.309-74.644,23.07-114.281,23.07
        s-78.087-7.762-114.28-23.07c-34.961-14.788-66.36-35.958-93.325-62.923s-48.135-58.363-62.922-93.324
        C14.81,377.898,7.048,339.449,7.048,299.812s7.762-78.087,23.071-114.28c14.787-34.961,35.957-66.36,62.922-93.325
        s58.364-48.135,93.325-62.922C222.559,13.976,261.009,6.214,300.646,6.214 M300.646,2.214
        C136.287,2.214,3.048,135.453,3.048,299.812S136.287,597.41,300.646,597.41s297.598-133.239,297.598-297.598
        S465.005,2.214,300.646,2.214L300.646,2.214z"/>
</g>
<g>
    <radialGradient id="SVGID_2_" cx="299.0464" cy="204.2632" r="368.0053" gradientUnits="userSpaceOnUse">
        <stop  offset="0" style="stop-color:#141414"/>
        <stop  offset="1" style="stop-color:#080808"/>
    </radialGradient>
    <path fill="url(#SVGID_2_)" d="M300.646,572.266c-72.775,0-141.194-28.34-192.654-79.8c-51.459-51.46-79.8-119.879-79.8-192.654
        s28.34-141.194,79.8-192.654s119.879-79.8,192.654-79.8s141.194,28.34,192.654,79.8c51.46,51.46,79.8,119.879,79.8,192.654
        s-28.34,141.194-79.8,192.654S373.421,572.266,300.646,572.266z"/>
    <path d="M300.646,29.358c36.512,0,71.931,7.15,105.271,21.252c32.205,13.622,61.129,33.123,85.968,57.962
        c24.84,24.839,44.341,53.763,57.963,85.968c14.102,33.34,21.252,68.759,21.252,105.271c0,36.512-7.15,71.931-21.252,105.271
        c-13.622,32.205-33.123,61.129-57.963,85.968c-24.839,24.84-53.763,44.341-85.968,57.963
        c-33.34,14.102-68.759,21.252-105.271,21.252c-36.513,0-71.931-7.15-105.271-21.252c-32.205-13.622-61.129-33.123-85.968-57.963
        c-24.839-24.839-44.34-53.763-57.962-85.968c-14.102-33.34-21.252-68.759-21.252-105.271c0-36.513,7.15-71.931,21.252-105.271
        c13.622-32.205,33.123-61.129,57.962-85.968s53.763-44.34,85.968-57.962C228.715,36.509,264.133,29.358,300.646,29.358
         M300.646,25.358c-151.577,0-274.454,122.877-274.454,274.454c0,151.576,122.877,274.454,274.454,274.454
        c151.576,0,274.454-122.878,274.454-274.454C575.1,148.235,452.222,25.358,300.646,25.358L300.646,25.358z"/>
</g>
<g>
    <radialGradient id="SVGID_3_" cx="299.5176" cy="232.4409" r="259.4771" gradientUnits="userSpaceOnUse">
        <stop  offset="0" style="stop-color:#212121"/>
        <stop  offset="1" style="stop-color:#0D0D0D"/>
    </radialGradient>
    <path fill="url(#SVGID_3_)" d="M300.646,491.916c-105.927,0-192.104-86.178-192.104-192.104
        c0-105.927,86.178-192.104,192.104-192.104c105.926,0,192.104,86.178,192.104,192.104
        C492.75,405.738,406.572,491.916,300.646,491.916z"/>
    <path d="M300.646,109.708c25.666,0,50.561,5.026,73.996,14.938c22.638,9.575,42.968,23.283,60.429,40.743
        c17.46,17.46,31.167,37.791,40.742,60.428c9.912,23.435,14.938,48.331,14.938,73.996s-5.025,50.561-14.938,73.996
        c-9.575,22.638-23.282,42.968-40.742,60.429c-17.461,17.46-37.791,31.167-60.429,40.742c-23.435,9.912-48.33,14.938-73.996,14.938
        s-50.562-5.025-73.996-14.938c-22.637-9.575-42.968-23.282-60.428-40.742c-17.46-17.461-31.168-37.791-40.743-60.429
        c-9.912-23.435-14.938-48.33-14.938-73.996s5.026-50.562,14.938-73.996c9.575-22.637,23.283-42.968,40.743-60.428
        s37.791-31.168,60.428-40.743C250.084,114.733,274.98,109.708,300.646,109.708 M300.646,105.708
        c-107.201,0-194.104,86.903-194.104,194.104c0,107.201,86.903,194.104,194.104,194.104c107.201,0,194.104-86.903,194.104-194.104
        C494.75,192.611,407.847,105.708,300.646,105.708L300.646,105.708z"/>
</g>
<g opacity="0.8">
    <path id="color-temp" fill="#BE1E2D" opacity="0" d="M300.646,489.309c-104.489,0-189.497-85.008-189.497-189.497c0-104.489,85.008-189.497,189.497-189.497
        c104.489,0,189.497,85.008,189.497,189.497C490.143,404.301,405.135,489.309,300.646,489.309z"/>
    <path d="M300.646,110.815c25.515,0,50.266,4.997,73.566,14.852c22.505,9.519,42.718,23.146,60.075,40.504
        s30.984,37.57,40.504,60.075c9.854,23.3,14.852,48.051,14.852,73.566s-4.997,50.266-14.852,73.566
        c-9.52,22.505-23.146,42.718-40.504,60.075s-37.57,30.984-60.075,40.504c-23.3,9.854-48.051,14.852-73.566,14.852
        s-50.266-4.997-73.566-14.852c-22.505-9.52-42.718-23.146-60.075-40.504s-30.985-37.57-40.504-60.075
        c-9.855-23.3-14.852-48.051-14.852-73.566s4.997-50.266,14.852-73.566c9.519-22.505,23.146-42.718,40.504-60.075
        s37.57-30.985,60.075-40.504C250.38,115.812,275.131,110.815,300.646,110.815 M300.646,109.815
        c-104.933,0-189.997,85.064-189.997,189.997c0,104.932,85.064,189.997,189.997,189.997c104.932,0,189.997-85.064,189.997-189.997
        C490.643,194.879,405.578,109.815,300.646,109.815L300.646,109.815z"/>
</g>
<g id="temperature-markings">
        <line fill="none" stroke="#C7C8CA" stroke-width="5" stroke-miterlimit="10"
              x1="300.646" y1="123.751" x2="300.646" y2="161.603"/>
        <line fill="none" stroke="#C7C8CA" stroke-width="5" stroke-miterlimit="10"
              x1="422.102" y1="371.971" x2="454.881" y2="390.896"/>
        <line fill="none" stroke="#C7C8CA" stroke-width="5" stroke-miterlimit="10"
              x1="146.41" y1="390.896" x2="179.191" y2="371.97"/>
</g>
<g id="temp-transform" transform="translate(300,300)">
        <line id="current-reading" fill="none" stroke="#FFFFFF"
              stroke-width="5" stroke-linecap="round"
              stroke-miterlimit="10" x1="0" y1="-180" x2="0" y2="-120"/>
</g>
    <text transform="matrix(1 0 0 1 254.1387 83.3198)" fill="#D1D3D4" font-family="'Arial'"
          font-weight="bold" font-size="29.4616">thermo</text>
</svg>


</div>


<script type="text/javascript">

    (function () {

        window.onload = loaded;

        function loaded() {
            var colorTemp = document.getElementById("color-temp");
            var reading = document.getElementById('current-reading');
            var currentAngle = 0;
            var fill;

            var direction = 1;
            setInterval(function () {
                currentAngle += direction;
                if (currentAngle >= 120 || currentAngle <= -120) {
                    direction *= -1;
                } else if (currentAngle === 0) {
                    fill = direction === 1 ? "#BE1E2D" : "#10A2DC";
                    colorTemp.setAttribute("fill", fill);
                }
                // adjust the opacity
                colorTemp.setAttribute("opacity", Math.abs(currentAngle) / 120.0);

                reading.setAttribute("transform", "rotate(" + currentAngle + ")");

            }, 25);
        }
    })();


</script>
</body>
</html>
by Aaron

You’re doing it wrong, alt text and title attributes

I had moved my mouse over an image on a local bank’s web site, and was surprised to see the name of the file pop-up.

SNAGHTML3867720c

The reason is that their web developer apparently doesn’t understand the meaning or intention behind the alt or title attribute of an HTML element.

Not that it isn’t handy to know the name of the file…. Smile

Maybe they could have used:

  • Passionate bank web site user
  • Man with loose tie
  • Man having good hair day
  • Or …. ?

(I noticed that they have this problem in many areas of their web site. Maybe their Banking skills are better than their web site skills?)