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Tuesday, January 17, 2012

Going Nuts with CSS Transitions

First we are going to make our images look like mini polaroids with captions. This means the logic is kept separate from the code that applies the polaroid effect. The polaroid class has no positioning, which allows it to be used generically anywhere that the effect is required. The pull classes set a float and add appropriate margins—they can be used for things like blockquotes as well.

 .polaroid {
  width: 150px;
  padding: 10px 10px 20px 10px;
  border: 1px solid #BFBFBF;
  background-color: white;
  -webkit-box-shadow: 2px 2px 3px rgba(135, 139, 144, 0.4);
  -moz-box-shadow: 2px 2px 3px rgba(135, 139, 144, 0.4);
  box-shadow: 2px 2px 3px rgba(135, 139, 144, 0.4);
}

The actual polaroid effect itself is simply applied using padding, a border and a background colour. We also apply a nice subtle box shadow, using a property that is supported by modern WebKit browsers and Firefox 3.5+. We include the box-shadow property last to ensure that future browsers that support the eventual CSS3 specified version natively will use that implementation over the legacy browser specific version.

The box-shadow property takes four values: three lengths and a colour. The first is the horizontal offset of the shadow—positive values place the shadow on the right, while negative values place it to the left. The second is the vertical offset, positive meaning below. If both of these are set to 0, the shadow is positioned equally on all four sides. The last length value sets the blur radius—the larger the number, the blurrier the shadow (therefore the darker you need to make the colour to have an effect). 

Rotation

For browsers that understand it (currently our old favourites WebKit and FF3.5+) we can add some visual flair by rotating the image, using the transform CSS 3 property.

-webkit-transform: rotate(9deg);
-moz-transform: rotate(9deg);
transform: rotate(9deg);

Rotations can be specified in degrees, radians (rads) or grads). WebKit also supports turns unfortunately Firefox doesn’t just yet.
For example we want any polaroid images on the left hand side to be rotated in the opposite direction, using a negative degree value:
.pull-left.polaroid {
-webkit-transform: rotate(-9deg);
-moz-transform: rotate(-9deg);
transform: rotate(-9deg);
}
Multiple class selectors don’t work in IE6 but as luck would have it, the transform property doesn’t work in any current IE version either. The above code is a good example of progressive enrichment: browsers that don’t support box-shadow or transform will still see the image and basic polaroid effect.


 For Live example


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