LESS mixins for vertical and horizontal gradients with ie9 fallbacks by @k88hudson

gradients.less

// Usage:
//  .gradient( "vertical", red, blue );         -> Creates a gradient from top = red to bottom = blue.
//  .gradient( "horizonal", red, blue );        -> Creates a gradient from left = red to right = blue.
//  .gradient( "vertical", red, blue, true );   -> Creates a gradient with a solid-color fallback. This is
//                                                 necessary for IE9 when the container has a border-radius of 2+
//                                                 or transparency.

._gradient( @color1, @color2, @startLoc, @endLoc, @from, @to, @ieFallback: false, @ieGradientType: 0 ) when ( @ieFallback ) {
  // Internal mixin for generating gradients when there are rounded corners
  background: @color1;
  background: -webkit-gradient( linear, @startLoc, @endLoc, color-stop( @from, @color1 ), color-stop( @to, @color2 ) );
  background: -webkit-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: -moz-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: -ms-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: -o-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: linear-gradient( @startLoc, @color1 );
}

._gradient( @color1, @color2, @startLoc, @endLoc, @from, @to, @ieFallback: false, @ieGradientType: 0 ) when not ( @ieFallback ) {
  // Internal mixin for generating gradients when there are no rounded corners
  filter: e( %( "progid:DXImageTransform.Microsoft.Gradient(startColorstr='%d', endColorstr='%d', GradientType=%d)", @color1, @color2, @ieGradientType ) );
  background: -webkit-gradient( linear, @startLoc, @endLoc, color-stop( @from, @color1 ), color-stop( @to, @color2 ) );
  background: -webkit-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: -moz-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: -ms-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: -o-linear-gradient( @startLoc, @color1 @from, @color2 @to );
  background: linear-gradient( @startLoc, @color1 );
}

.gradient( "vertical", @color1, @color2, @fallback: false ) {
  ._gradient( @color1, @color2, top, bottom, 0%, 100%, @fallback, 0 );
}

.gradient( "horizontal", @color1, @color2, @fallback: false ) {
  ._gradient( @color1, @color2, left, right, 0%, 100%, @fallback, 1 );
}