Search code examples
svgtransforminkscape

What does inkscape:transform-center-x/y means?

I am using Inkscape to make SVG image and a little confused about the "transform-center-x" attribute like below:

    <circle
           style="display:inline;fill:#0000ff;fill-opacity:1;stroke:#000000;stroke-width:1.13386"
           id="beacon-21737"
           cx="-121.04593"
           cy="42.20393"
           r="1.9999999"
           inkscape:transform-center-x="-0.6614634"
           inkscape:transform-center-y="-10.318751"
           inkscape:label="beacon"
           transform="rotate(-90)">
    </circle>

It seems not equal to rotate(angle, x, y). Please help me understand the meaning of the "transform-center-x/y".

Solution

  • This is a property of the grafical interface. If you click twice on a grafical object, you can rotate or skew it around a center indicated by a cross:

    Inkscape rotate and skew representation

    The cross can be moved by dragging it. Its position is stored in the inkscape:transform-center attribute. The value is in coordinates relative to the center of the bounding box of the grafical object. This position will also be used for other transforms, for example when you use the Object -> Transformation... dialog.

    The SVG namespace transform will not reflect that center. Inkscape has an internal optimization algorithm to express rotations and other transforms, so the grafical and the standardized center might not coincide.

    As always, other renderers will simply ignore tags and attributes in the inkscape namespace.