DOMMatrixReadOnly.scale() - Web APIs 编辑

Experimental

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The scale() method of the DOMMatrixReadOnly interface creates a new matrix being the result of the original matrix with a scale transform applied.

The scale() method is specified with either one or six values.

DOMMatrix.scale(scaleX[, scaleY][, scaleZ][, originX][, originY][, originZ])

scaleX

A multiplier for the scale value on the x-axis.

scaleY Optional

A multiplier for the scale value on the y-axis.  If not supplied, this defaults to the value of scaleX.

scaleZ Optional

A multiplier for the scale value on the z-axis.  If this value is anything other than 1, the resulting matrix will be 3D.

originX Optional

An x-coordinate for the origin of the transformation.  If no origin is supplied, this defaults to 0.

originY Optional

A y-coordinate for the origin of the transformation.  If no origin is supplied, this defaults to 0.

originZ Optional

A z-coordinate for the origin of the transformation.  If no origin is supplied, this defaults to 0. If this value is anything other than 0, the resulting matrix will be 3D.

Returns a DOMMatrix containing a new matrix being the result of the matrix x and y dimensions being scaled by the given factor, centered on the origin given. The original matrix is not modified.

If a scale is applied about the z-axis, the resulting matrix will be a 4x4 3D matrix.

Note: At time of writing, Firefox still supports an older version of the specification that accepts either one or three values.

DOMMatrix.scale(scale[, originX][, originY])

We'll show an example of how you can deal with the cross-browser support implications of this in the Examples section, below.

This SVG contains three squares, one red, one blue, and one green, each positioned at the document origin:

<svg width="250" height="250" viewBox="0 0 25 25">
  <rect width="25" height="25" fill="red" />
  <rect id="transformed" width="25" height="25" fill="blue" />
  <rect id="transformedOrigin" width="25" height="25" fill="green" />
</svg>

This JavaScript first creates an identity matrix, then uses the scale() method to create a new matrix with a single parameter. 

We test if the browser supports a six parameter scale() method by creating a new matrix using three parameters and observing it's is2D property — if this is false then the third parameter has been accepted by the browser as a scaleZ parameter, making this a 3D matrix.

We then create a new matrix scaled about a given origin, using either three or six parameters depending on the browser support.

These new matrices are then applied to the blue and green squares as a transform, changing their dimensions and position. The red square is left in place.

const matrix = new DOMMatrixReadOnly();
const scaledMatrix = matrix.scale(0.5);

let scaledMatrixWithOrigin = matrix.scale(0.5, 25, 25);

// if the browser has interpreted these parameters as scaleX, scaleY, scaleZ, the resulting matrix is 3D
const browserExpectsSixParamScale = !scaledMatrixWithOrigin.is2D;
if (browserExpectsSixParamScale) {
  scaledMatrixWithOrigin = matrix.scale(0.5, 0.5, 1, 25, 25, 0);
}

document.querySelector('#transformed').setAttribute('transform', scaledMatrix.toString());
document.querySelector('#transformedOrigin').setAttribute('transform', scaledMatrixWithOrigin.toString());

Screenshot	Live sample