We may add more filter functions later:
  <li>brightness, contrast, exposure</li>
  <li>halftone</li>
  <li>motion-blur(radius, angle)</li>
  <li>posterize(levels)</li>
  <li>bump(x, y, radius, intensity)</li>
  <li>generators</li>
  <li>circle-crop(x, y, radius)</li>
  <li>affine-transform(some matrix)</li>
  <li>crop(x, y, w, h)</li>
  <li>bloom(radius, intensity)</li>
  <li>gloom(radius, intensity)</li>
  <li>mosaic(w,h)</li>
  <li>displace(url, intensity)</li>
  <li>edge-detect(intensity)</li>
  <li>pinch(x, y, radius, scale)</li>
  <li>twirl(x, y, radius, angle)</li>