SVGClipPathElement: transform プロパティ

html,
body,
svg {
  height: 100%;
}

<div>
  <svg viewBox="0 0 100 100" width="200" height="200">
    <clipPath
      id="clip1"
      clipPathUnits="objectBoundingBox"
      transform="skewX(40) scale(1 0.5)">
      <circle cx=".5" cy=".5" r=".35" />
    </clipPath>
    <rect id="r1" x="0" y="0" width="100" height="100" />
    <use clip-path="url(#clip1)" href="#r1" fill="lightblue" />
  </svg>
</div>
<pre id="log"></pre>

const translateType = [
  "unknown",
  "matrix()",
  "translate()",
  "scale()",
  "rotate()",
  "skewx()",
  "skewy()",
];
const clipPath1 = document.getElementById("clip1");
const log = document.getElementById("log");
let result = "次の座標変換が適用されています。\n";
for (const transform of clipPath1.transform.baseVal) {
  result += `- '${translateType[transform.type]}' 型の座標変換が見つかりました。\n`;
}
log.textContent = result;