activeadmin-quill_editor/app/assets/stylesheets/activeadmin/quill.imageUploader.css

.image-uploading {
  position: relative;
  display: inline-block;
}

.image-uploading img {
  max-width: 98% !important;
  filter: blur(5px);
  opacity: 0.3;
}

.image-uploading::before {
  content: "";
  box-sizing: border-box;
  position: absolute;
  top: 50%;
  left: 50%;
  width: 30px;
  height: 30px;
  margin-top: -15px;
  margin-left: -15px;
  border-radius: 50%;
  border: 3px solid #ccc;
  border-top-color: #1e986c;
  z-index: 1;
  animation: spinner 0.6s linear infinite;
}

@keyframes spinner {
  to {
    transform: rotate(360deg);
  }
}