getShader method
Creates an ImageShader from the symbol image.
This is used to create pattern fills for areas and polylines.
Implementation
ui.ImageShader getShader() {
// final double devicePixelRatio = ui.window.devicePixelRatio;
// final Float64List deviceTransform = new Float64List(16)
// ..[0] = devicePixelRatio
// ..[5] = devicePixelRatio
// ..[10] = 1.0
// ..[15] = 2.0;
return ui.ImageShader(_image, ui.TileMode.repeated, ui.TileMode.repeated, Matrix4.identity().storage);
}