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SVG getScreenCTM

  1. const el = document.body.appendChild(
  2.   document.createElement`div`
  3. );
  4. el.innerHTML = `
  5. <svg width="200" height="200" viewBox="0 0 200 200">
  6.   <rect 
  7.     class="rect"
  8.     transform="translate(50, 50) scale(1.2) rotate(25)"
  9.     fill="purple"
  10.     x="0" y="0" width="50" height="50" />
  11. </svg>
  12. `;
  13.  
  14. const box = document.body.appendChild(
  15.   document.createElement`div`
  16. );
  17.  
  18. Object.assign(box.style, {
  19.   position: 'absolute',
  20.   left: 0, top: 0,
  21.   width: '50px',
  22.   height: '50px',
  23.   transformOrigin: '0 0',
  24.   outline: '5px solid red'
  25. });
  26.  
  27. const rect = document.querySelector('.rect');
  28. const {a, b, c, d, e, f} = rect.getScreenCTM()
  29.  
  30. box.style.transform = `
  31.   matrix(${[a, b, c, d, e, f]})
  32. `;

The transformation matrix of an SVG element can be obtained using getScreenCTM or getCTM. The latter of which will be relative to the SVG coordinate space, vs the coordinate space of the page.

Here we take the matrix data from getScreenCTM and use it on a div to place a border over an SVG rect node. This is great for layering HTML on top of SVG.

// dom // javascript // math // matrix // svg // tricks // ui
snippet.zone ~ 2021-22 /// {s/z}