a:xfrm (2D Transform)

Description

\:xfrm\ is the DrawingML element that defines 2D transformations (position, size, rotation, flipping) for shapes. It is defined in ECMA-376 Part 1 §20.1.7.5.

2D transforms are fundamental to shape geometry and are used for:

• Positioning shapes at specific coordinates
• Sizing shapes to exact dimensions
• Rotating shapes by specific angles
• Flipping shapes horizontally or vertically
• Defining child coordinate systems in groups
• Creating precise layout and positioning

The \:xfrm\ element contains:

• Offset (\:off) — X, Y position
• Extents (\:ext) — Width, height
• Optional: Flip flags (flipH, flipV) and rotation (rot)
• For groups: Child offset (\:chOff) and child extents (\:chExt)

Attributes

Note: Rotation is stored in 1/60,000° units (e.g., 5400000 = 90°).

Content Model

\:xfrm\ structure:

1. a:off (required, 1) — Offset (position) of shape
2. a:ext (required, 1) — Extents (size) of shape
3. a:chOff (optional, 0–1) — Child offset (for groups only)
4. a:chExt (optional, 0–1) — Child extents (for groups only)

Child Elements Table

Examples

Basic Shape Positioning and Sizing

<a:xfrm>
  <a:off x="1000000" y="1000000"/>
  <a:ext cx="5000000" cy="3000000"/>
</a:xfrm>

using DocumentFormat.OpenXml.Drawing;

var transform = new Transform2D();
transform.Append(new Offset { X = 1000000, Y = 1000000 });
transform.Append(new Extents { Cx = 5000000, Cy = 3000000 });

// Attach to shape properties
var spPr = new ShapeProperties();
spPr.Append(transform);

Rotated Shape (90 Degrees)

<a:xfrm rot="5400000">
  <a:off x="2000000" y="2000000"/>
  <a:ext cx="3000000" cy="2000000"/>
</a:xfrm>

var transform = new Transform2D { Rotation = 5400000 };  // 90°
transform.Append(new Offset { X = 2000000, Y = 2000000 });
transform.Append(new Extents { Cx = 3000000, Cy = 2000000 });

Horizontally Flipped Shape

<a:xfrm flipH="1">
  <a:off x="1500000" y="1500000"/>
  <a:ext cx="4000000" cy="2500000"/>
</a:xfrm>

var transform = new Transform2D { HorizontalFlip = true };
transform.Append(new Offset { X = 1500000, Y = 1500000 });
transform.Append(new Extents { Cx = 4000000, Cy = 2500000 });

Vertically Flipped and Rotated

<a:xfrm rot="2700000" flipV="1">
  <a:off x="2000000" y="2000000"/>
  <a:ext cx="3000000" cy="2000000"/>
</a:xfrm>

var transform = new Transform2D 
{ 
  Rotation = 2700000,      // -90° (270° counter-clockwise)
  VerticalFlip = true
};
transform.Append(new Offset { X = 2000000, Y = 2000000 });
transform.Append(new Extents { Cx = 3000000, Cy = 2000000 });

Group Shape with Child Coordinate System

<a:grpSpPr>
  <a:xfrm>
    <!-- Group position and size -->
    <a:off x="0" y="0"/>
    <a:ext cx="10000000" cy="8000000"/>
    <!-- Child coordinate system (defines local coordinates for children) -->
    <a:chOff x="0" y="0"/>
    <a:chExt cx="10000000" cy="8000000"/>
  </a:xfrm>
</a:grpSpPr>

var grpSpPr = new GroupShapeProperties();
var transform = new Transform2D();

// Group position and size
transform.Append(new Offset { X = 0, Y = 0 });
transform.Append(new Extents { Cx = 10000000, Cy = 8000000 });

// Child coordinate system
transform.Append(new ChildOffset { X = 0, Y = 0 });
transform.Append(new ChildExtents { Cx = 10000000, Cy = 8000000 });

grpSpPr.Append(transform);

Scaled Group (Child Scaling)

<a:grpSpPr>
  <a:xfrm>
    <!-- Group occupies 10M × 8M on slide -->
    <a:off x="1000000" y="1000000"/>
    <a:ext cx="10000000" cy="8000000"/>
    <!-- But children use 5M × 4M coordinate space (2× scaling) -->
    <a:chOff x="0" y="0"/>
    <a:chExt cx="5000000" cy="4000000"/>
  </a:xfrm>
</a:grpSpPr>

var grpSpPr = new GroupShapeProperties();
var transform = new Transform2D();

// Group displayed at 10M × 8M
transform.Append(new Offset { X = 1000000, Y = 1000000 });
transform.Append(new Extents { Cx = 10000000, Cy = 8000000 });

// Children in 5M × 4M space → automatically scaled 2×
transform.Append(new ChildOffset { X = 0, Y = 0 });
transform.Append(new ChildExtents { Cx = 5000000, Cy = 4000000 });

grpSpPr.Append(transform);

Rotation Reference

Rotation values are in 1/60,000° units:

Formula: EMU = Degrees × 60000

Position and Size Units

Dimensions in \:xfrm\ use English Metric Units (EMUs):

Coordinate System: Origin (0,0) at top-left; X increases right, Y increases down.

Transform Properties

Flip Combinations

Group Child Coordinate System

Groups define local coordinate spaces for children:

` Parent (Slide) Coordinates: 10M × 8M ↓ Group Transform (a:grpSpPr/a:xfrm) ↓ Child Coordinate Space (a:chOff/a:chExt): 5M × 4M ↓ Children positioned in local 5M × 4M space ↓ Automatically scaled 2× to fill 10M × 8M group area `

This enables:

• Nested scaling: Children scale with group resize
• Local coordinates: Children use simple child space, not absolute coordinates
• Responsive design: Resize group, children auto-scale

Common Patterns

Centered Shape

xml <!-- Center 4M × 3M shape on 10M × 8M canvas --> <a:xfrm> <a:off x="3000000" y="2500000"/> <a:ext cx="4000000" cy="3000000"/> </a:xfrm>

Full-Screen Shape

xml <a:xfrm> <a:off x="0" y="0"/> <a:ext cx="9144000" cy="6858000"/> </a:xfrm>

Rotated Text Box (45°)

xml <a:xfrm rot="2700000"> <a:off x="1000000" y="1000000"/> <a:ext cx="4000000" cy="2000000"/> </a:xfrm>

Notes

Element Characteristics

• Required in all shapes: Every shape must have \:xfrm\
• Child extents (group-only): Define coordinate system for child shapes
• Rotation is global: Applied after position/size; origin at shape center
• Flipping: Applied independently; both can be set simultaneously
• Immutable in edit: Most Office apps recalculate on resize/rotate

Coordinate System Details

• Origin (0,0) at top-left of parent/slide
• X increases rightward
• Y increases downward
• Negative coordinates allowed (off-canvas positioning)
• Rotation origin: Shape center

Rendering

• Word: Position and size follow \:xfrm\ exactly
• PowerPoint: Animations/interactions respect transform
• Excel: Limited rotation support (some older versions)
• Publisher: Full transform support

Interaction with Shape Geometry

• Transform applies to bounding box (not geometry path)
• Shape geometry is relative to bounding box
• Combined: geometry + transform = final rendered shape

Best Practices

• Use EMU values consistently throughout document
• Store rotation angle separately for easy conversion
• For groups, define child extents for proper scaling
• Avoid extreme rotations (>180°); use -180° to 180° range
• Consider accessibility; rotated/flipped text may affect readability
• Document coordinate systems for complex grouped designs