a:softEdge (Soft Edge Effect)

Description

a:softEdge is the DrawingML soft edge effect element that creates feathered, softly blurred edges on a shape. It is defined in ECMA-376 Part 1 §20.1.8.10.

Soft edge effects create smooth, professional-looking transitions between the shape and its background by:

• Gradually fading shape transparency at the edges
• Creating soft, feathered boundaries
• Controlling the blur radius to adjust softness
• Maintaining shape readability while adding sophistication

Soft edges are useful for:

• Creating elegant, professional presentations
• Softening harsh shape boundaries
• Adding visual polish to diagrams and illustrations
• Creating layered, modern design effects
• Improving visual harmony in documents

Attributes

Examples

Subtle Soft Edge

<a:effectLst>
  <a:softEdge rad="50800">
  </a:softEdge>
</a:effectLst>

using DocumentFormat.OpenXml.Drawing;

var effectLst = new EffectList();
var softEdge = new SoftEdge { Radius = 50800 }; // ~0.055 inch blur
effectLst.Append(softEdge);

Strong Soft Edge Feathering

<a:effectLst>
  <a:softEdge rad="152400">
  </a:softEdge>
</a:effectLst>

var effectLst = new EffectList();
var softEdge = new SoftEdge { Radius = 152400 }; // ~0.166 inch blur
effectLst.Append(softEdge);

Combined Soft Edge and Inner Shadow

<a:effectLst>
  <a:softEdge rad="76200"/>
  <a:innerShdw blurRad="50800" dist="38100" dir="2700000">
    <a:srgbClr val="000000">
      <a:alpha val="50000"/>
    </a:srgbClr>
  </a:innerShdw>
</a:effectLst>

var effectLst = new EffectList();

var softEdge = new SoftEdge { Radius = 76200 };
effectLst.Append(softEdge);

var innerShdw = new InnerShadow 
{ 
  BlurRadius = 50800, 
  Distance = 38100, 
  Direction = 2700000 
};
var srgbClr = new RgbColorModelHex { Val = "000000" };
var alpha = new Alpha { Val = 50000 };
srgbClr.Append(alpha);
innerShdw.Append(srgbClr);
effectLst.Append(innerShdw);

Notes

• Radius is in EMUs (914400 EMUs = 1 inch)
• Typical soft edge radius: 38100 (subtle) to 381000 (very soft)
• Larger radius values create more pronounced feathering
• Soft edges are cumulative - they affect edges of shapes with any fill
• Works well with solid fills, gradients, and patterns
• Can be combined with other effects (shadow, glow, reflection)
• Performance impact minimal compared to complex shadows
• Text within soft-edged shapes remains sharp and readable