c# NPOI 如何在指定單元格導入導出圖片

Intro

我維護瞭一個 NPOI 的擴展(WeihanLi.Npoi),主要用來導入導出 Excel 數據,最近有網友提出瞭導入 Excel 的時候解析圖片的需求,於是就有瞭本文的探索

導入Excel 時解析圖片

xls 和 xlsx 的 API 稍有不同,詳細可以直接參考以下代碼,實現代碼如下:

public static Dictionary<CellPosition, IPictureData> GetPicturesAndPosition(this ISheet sheet)
{
  var dictionary = new Dictionary<CellPosition, IPictureData>();
  if (sheet.Workbook is HSSFWorkbook)
  {
    foreach (var shape in ((HSSFPatriarch)sheet.DrawingPatriarch).Children)
    {
      if (shape is HSSFPicture picture)
      {
        var position = new CellPosition(picture.ClientAnchor.Row1, picture.ClientAnchor.Col1);
        dictionary[position] = picture.PictureData;
      }
    }
  }
  else if (sheet.Workbook is XSSFWorkbook)
  {
    foreach (var shape in ((XSSFDrawing)sheet.DrawingPatriarch).GetShapes())
    {
      if (shape is XSSFPicture picture)
      {
        var position = new CellPosition(picture.ClientAnchor.Row1, picture.ClientAnchor.Col1);
        dictionary[position] = picture.PictureData;
      }
    }
  }
  return dictionary;
}

CellPosition 是一個自定義的結構體,表示當前單元格的位置,源碼如下:

public readonly struct CellPosition : IEquatable<CellPosition>
{
  public CellPosition(int row, int col)
  {
    Row = row;
    Column = col;
  }

  public int Row { get; }
  public int Column { get; }

  public bool Equals(CellPosition other)
  {
    return Row == other.Row && Column == other.Column;
  }

  public override bool Equals(object? obj) => obj is CellPosition other && Equals(other);

  public override int GetHashCode() => $"{Row}_{Column}".GetHashCode();
}

根據上面的代碼,我們就可以獲取到獲取到所有的圖片以及圖片的所在位置,這樣根據單元格位置去找圖片信息的時候就會很方便瞭

導出 Excel 時設置圖片

實現代碼如下:

public static bool TryAddPicture(this ISheet sheet, int row, int col, byte[] pictureBytes, PictureType pictureType = PictureType.PNG)
{
  if (sheet is null)
  {
    throw new ArgumentNullException(nameof(sheet));
  }

  try
  {
    var pictureIndex = sheet.Workbook.AddPicture(pictureBytes, pictureType);

    var clientAnchor = sheet.Workbook.GetCreationHelper().CreateClientAnchor();
    clientAnchor.Row1 = row;
    clientAnchor.Col1 = col;

    var picture = (sheet.DrawingPatriarch ?? sheet.CreateDrawingPatriarch())
      .CreatePicture(clientAnchor, pictureIndex);
    picture.Resize();
    return true;
  }
  catch (Exception e)
  {
    Debug.WriteLine(e);
  }

  return false;
}

通過上面的代碼我們就可以在指定的單元格設置圖片,目前沒有支持單元格合並操作,有需要自己進行修改

WeihanLi.Npoi

WeihanLi.Npoi 在 1.15.0 版本中增加瞭圖片導入導出的支持,使用示例可以參考下面的單元測試:

[Theory]
[ExcelFormatData]
public async Task ImageImportExportTest(ExcelFormat excelFormat)
{
  using var httpClient = new HttpClient();
  var imageBytes = await httpClient.GetByteArrayAsync("https://weihanli.xyz/assets/avator.jpg");
  var list = Enumerable.Range(1, 5)
    .Select(x => new ImageTest() { Id = x, Image = imageBytes })
    .ToList();
  var excelBytes = list.ToExcelBytes(excelFormat);
  var importResult = ExcelHelper.ToEntityList<ImageTest>(excelBytes, excelFormat);
  Assert.NotNull(importResult);
  Assert.Equal(list.Count, importResult.Count);
  for (var i = 0; i < list.Count; i++)
  {
    Assert.NotNull(importResult[i]);
    var result = importResult[i]!;
    Assert.Equal(list[i].Id, result.Id);
    Assert.NotNull(result.Image);
    Assert.True(list[i].Image.SequenceEqual(result.Image));
  }
}

private class ImageTest
{
  public int Id { get; set; }

  public byte[] Image { get; set; } = null!;
}

導入時會自動將 byte[] 類型的屬性嘗試獲取對應的單元格位置的圖片,如果在對應的位置找到瞭圖片就能夠讀取到圖片的字節數組信息映射到 model 裡的字節數組屬性

除此之外,還支持直接導入的時候將圖片信息 Map 到 IPictureData 屬性上,但是覺得還是字節數組更通用一些,如果對此感興趣可以參考項目源碼以及單元測試

More

感謝 @ZeguangZhang94 童鞋提出的需求和幫忙測試~

如果你也有類似的讀取指定單元格的圖片或者在指定單元格插入圖片的需求,可以試一下上面的方法,希望對你有幫助,可以直接引用我的類庫或者直接拷貝源碼到自己的項目裡使用

References

  • https://github.com/WeihanLi/WeihanLi.Npoi
  • https://github.com/WeihanLi/WeihanLi.Npoi/blob/dev/src/WeihanLi.Npoi/NpoiExtensions.cs#L1143
  • https://stackoverflow.com/questions/24084129/read-image-from-excel-file-using-npoi
  • https://stackoverflow.com/questions/41138848/add-image-to-excel-xlsx-using-npoi-c-sharp
  • https://github.com/WeihanLi/WeihanLi.Npoi/issues/99

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