dxf/src/util/transformBoundingBoxAndElement.js

DXF parser for node/browser

import { Box2 } from 'vecks'

/**
 * Transform the bounding box and the SVG element by the given
 * transforms. The <g> element are created in reverse transform
 * order and the bounding box in the given order.
 */
export default (bbox, element, transforms) => {
  let transformedElement = ''
  const matrices = transforms.map((transform) => {
    // Create the transformation matrix
    const tx = transform.x || 0
    const ty = transform.y || 0
    const sx = transform.scaleX || 1
    const sy = transform.scaleY || 1
    const angle = ((transform.rotation || 0) / 180) * Math.PI
    const { cos, sin } = Math
    let a, b, c, d, e, f
    // In DXF an extrusionZ value of -1 denote a tranform around the Y axis.
    if (transform.extrusionZ === -1) {
      a = -sx * cos(angle)
      b = sx * sin(angle)
      c = sy * sin(angle)
      d = sy * cos(angle)
      e = -tx
      f = ty
    } else {
      a = sx * cos(angle)
      b = sx * sin(angle)
      c = -sy * sin(angle)
      d = sy * cos(angle)
      e = tx
      f = ty
    }
    return [a, b, c, d, e, f]
  })

  // Only transform the bounding box is it is valid (i.e. not Infinity)
  let transformedBBox = new Box2()
  if (bbox.valid) {
    let bboxPoints = [
      { x: bbox.min.x, y: bbox.min.y },
      { x: bbox.max.x, y: bbox.min.y },
      { x: bbox.max.x, y: bbox.max.y },
      { x: bbox.min.x, y: bbox.max.y },
    ]
    matrices.forEach(([a, b, c, d, e, f]) => {
      bboxPoints = bboxPoints.map((point) => ({
        x: point.x * a + point.y * c + e,
        y: point.x * b + point.y * d + f,
      }))
    })
    transformedBBox = bboxPoints.reduce((acc, point) => {
      return acc.expandByPoint(point)
    }, new Box2())
  }

  matrices.reverse()
  matrices.forEach(([a, b, c, d, e, f]) => {
    transformedElement += `<g transform="matrix(${a} ${b} ${c} ${d} ${e} ${f})">`
  })
  transformedElement += element
  matrices.forEach((transform) => {
    transformedElement += '</g>'
  })

  return { bbox: transformedBBox, element: transformedElement }
}