/**
 * 将指定区域的canvas转换为base64格式的图片
 */
export function saveCanvasToBase64(
  context: CanvasRenderingContext2D,
  startX: number,
  startY: number,
  width: number,
  height: number,
  quality = 0.75
) {
  // 获取裁剪框区域图片信息
  const img = context.getImageData(startX, startY, width, height);
  // 创建canvas标签，用于存放裁剪区域的图片
  const canvas = document.createElement("canvas");
  canvas.width = width;
  canvas.height = height;
  // 获取裁剪框区域画布
  const imgContext = canvas.getContext("2d");
  if (imgContext) {
    // 将图片放进canvas中
    imgContext.putImageData(img, 0, 0);
    // 将图片自动添加至剪贴板中
    canvas?.toBlob(
      blob => {
        if (blob == null) return;
        const Clipboard = window.ClipboardItem;
        // 浏览器不支持Clipboard
        if (Clipboard == null) return canvas.toDataURL("png");
        const clipboardItem = new Clipboard({
          [blob.type]: blob
        });
        navigator.clipboard?.write([clipboardItem]).then(() => {
          return "写入成功";
        });
      },
      "image/png",
      quality
    );
    return canvas.toDataURL("png");
  }
  return "";
}