/* SVG 转 PNG */
textarea.sp-area{min-height:11rem;font-size:.8125rem;line-height:1.6}
.sp-preview{display:flex;align-items:center;justify-content:center;min-height:9rem;padding:1rem;border:1px solid #eef1f5;border-radius:.6rem;
  background:linear-gradient(45deg,#f7f8fa 25%,transparent 25%,transparent 75%,#f7f8fa 75%),
             linear-gradient(45deg,#f7f8fa 25%,#fff 25%,#fff 75%,#f7f8fa 75%);
  background-size:16px 16px;background-position:0 0,8px 8px}
.sp-preview img{display:block;max-width:100%;max-height:20rem;height:auto}