c# NPOI 如何在指定单元格导入导出图片

好的！下面是关于“c# NPOI 如何在指定单元格导入导出图片”的完整攻略。

1. 背景

NPOI是一款用于操作office文档的开源组件，它支持对Word、Excel、PowerPoint等文件的读取和写入。在Excel文件中，常常需要在单元格中插入图片，并且在需要时可以导出这些图片。本攻略将介绍如何使用c# NPOI在指定单元格中导入导出图片。

2. 导入图片

首先，我们需要将图片导入到Excel文件中。这可以通过以下步骤实现：

2.1 使用MemoryStream将图片转换为byte数组

MemoryStream ms = new MemoryStream();
Bitmap bmp = new Bitmap(imageFilePath);
bmp.Save(ms, ImageFormat.Jpeg);
byte[] imageData = ms.ToArray();

2.2 在单元格中插入图片

使用NPOI的HSSFWorkbook或XSSFWorkbook对象，可以很容易地在Excel文件中插入图片：

HSSFCellStyle style = (HSSFCellStyle)workbook.CreateCellStyle();
style.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;
style.VerticalAlignment = NPOI.SS.UserModel.VerticalAlignment.Center;
HSSFPatriarch patriarch = (HSSFPatriarch)sheet.CreateDrawingPatriarch();
HSSFClientAnchor anchor = new HSSFClientAnchor(0, 0, 0, 0, column, row, column, row);
anchor.AnchorType = AnchorType.MoveAndResize;

int pictureIndex = workBook.AddPicture(imageData, PictureType.JPEG);
HSSFPicture picture = patriarch.CreatePicture(anchor, pictureIndex);
picture.Resize();
picture.LineStyle = LineStyle.None;

其中，column和row分别是想要将图片插入的单元格的列和行索引。

3. 导出图片

接下来，我们需要导出已经插入到Excel文件中的图片。这可以通过以下步骤实现：

3.1 获取单元格中插入的图片

使用NPOI的HSSFPatriarch对象，可以获取指定单元格中插入的图片：

HSSFPatriarch patriarch = (HSSFPatriarch)sheet.CreateDrawingPatriarch();
HSSFClientAnchor anchor = patriarch.GetClientAnchorForPic(picture);
int pictureIndex = anchor.GetPictureIndex();

其中，picture是指想要获取的图片。

3.2 导出图片

使用NPOI的HSSFWorkbook或XSSFWorkbook对象，可以将图片导出到本地文件：

HSSFPictureData pictureData = (HSSFPictureData)workbook.GetAllPictures()[pictureIndex];
string extension = pictureData.SuggestFileExtension();
string fileName = "picture." + extension;
using (var fs = new FileStream(fileName, FileMode.Create, FileAccess.Write))
{
    fs.Write(pictureData.Data, 0, pictureData.Data.Length);
}

通过pictureIndex获取到pictureData，然后通过SuggestFileExtension()方法获取图片格式的扩展名。最后通过FileStream将pictureData.Data写入到一个文件中，即可完成图片的导出操作。

4. 示例说明

下面给出两个示例，分别演示如何在指定单元格中导入图片和如何导出图片。

4.1 示例1：导入图片

using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.SS.Util;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace TestApp
{
    class Program
    {
        static void Main(string[] args)
        {
            HSSFWorkbook workbook = new HSSFWorkbook();
            ISheet sheet = workbook.CreateSheet("Sheet1");

            // 导入图片
            string imageFilePath = "C:/test/image.jpg";
            byte[] imageData = GetImageData(imageFilePath);
            InsertImage(workbook, sheet, imageData, 2, 2);

            // 保存Excel文件
            FileStream fs = new FileStream("C:/test/Book1.xls", FileMode.Create, FileAccess.Write);
            workbook.Write(fs);
            fs.Close();
        }

        static byte[] GetImageData(string imageFilePath)
        {
            MemoryStream ms = new MemoryStream();
            Bitmap bmp = new Bitmap(imageFilePath);
            bmp.Save(ms, ImageFormat.Jpeg);
            byte[] imageData = ms.ToArray();
            return imageData;
        }

        static void InsertImage(HSSFWorkbook workbook, ISheet sheet, byte[] imageData, int row, int column)
        {
            HSSFCellStyle style = (HSSFCellStyle)workbook.CreateCellStyle();
            style.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;
            style.VerticalAlignment = NPOI.SS.UserModel.VerticalAlignment.Center;
            HSSFPatriarch patriarch = (HSSFPatriarch)sheet.CreateDrawingPatriarch();
            HSSFClientAnchor anchor = new HSSFClientAnchor(0, 0, 0, 0, column, row, column, row);
            anchor.AnchorType = AnchorType.MoveAndResize;

            int pictureIndex = workbook.AddPicture(imageData, PictureType.JPEG);
            HSSFPicture picture = patriarch.CreatePicture(anchor, pictureIndex);
            picture.Resize();
            picture.LineStyle = LineStyle.None;
        }
    }
}

在该示例中，我们从本地文件系统中获取一张图片，然后调用InsertImage方法将图片插入到单元格（2,2）中。最后保存Excel文件。

4.2 示例2：导出图片

using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using System;
using System.IO;

namespace TestApp
{
    class Program
    {
        static void Main(string[] args)
        {
            HSSFWorkbook workbook = new HSSFWorkbook();
            ISheet sheet = workbook.CreateSheet("Sheet1");

            // 导入图片
            string imageFilePath = "C:/test/image.jpg";
            byte[] imageData = GetImageData(imageFilePath);
            InsertImage(workbook, sheet, imageData, 2, 2);

            // 导出图片
            ExportImage(workbook, 2, 2);

            // 保存Excel文件
            FileStream fs = new FileStream("C:/test/Book1.xls", FileMode.Create, FileAccess.Write);
            workbook.Write(fs);
            fs.Close();
        }

        static byte[] GetImageData(string imageFilePath)
        {
            MemoryStream ms = new MemoryStream();
            Bitmap bmp = new Bitmap(imageFilePath);
            bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            byte[] imageData = ms.ToArray();
            return imageData;
        }

        static void InsertImage(HSSFWorkbook workbook, ISheet sheet, byte[] imageData, int row, int column)
        {
            HSSFCellStyle style = (HSSFCellStyle)workbook.CreateCellStyle();
            style.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;
            style.VerticalAlignment = NPOI.SS.UserModel.VerticalAlignment.Center;
            HSSFPatriarch patriarch = (HSSFPatriarch)sheet.CreateDrawingPatriarch();
            HSSFClientAnchor anchor = new HSSFClientAnchor(0, 0, 0, 0, column, row, column, row);
            anchor.AnchorType = AnchorType.MoveAndResize;

            int pictureIndex = workbook.AddPicture(imageData, PictureType.JPEG);
            HSSFPicture picture = patriarch.CreatePicture(anchor, pictureIndex);
            picture.Resize();
            picture.LineStyle = LineStyle.None;
        }

        static void ExportImage(HSSFWorkbook workbook, int row, int column)
        {
            HSSFPatriarch patriarch = (HSSFPatriarch)workbook.GetSheet("Sheet1").CreateDrawingPatriarch();
            HSSFPicture picture = null;

            for (int i = 0; i < patriarch.Children.Count; i++)
            {
                if (patriarch.Children[i] is HSSFPicture)
                {
                    picture = (HSSFPicture)patriarch.Children[i];
                    HSSFClientAnchor anchor = patriarch.GetClientAnchorForPic(picture);
                    if (anchor.Row1 == row && anchor.Col1 == column)
                    {
                        HSSFPictureData pictureData = (HSSFPictureData)workbook.GetAllPictures()[picture.PictureIndex];
                        string extension = pictureData.SuggestFileExtension();
                        string fileName = "C:/test/picture." + extension;
                        using (var fs = new FileStream(fileName, FileMode.Create, FileAccess.Write))
                        {
                            fs.Write(pictureData.Data, 0, pictureData.Data.Length);
                        }
                        break;
                    }
                }
            }
        }
    }
}

在该示例中，我们先用InsertImage方法将图片插入到单元格（2,2）中，然后调用ExportImage方法将图片导出到本地文件系统中。

综上，以上就是如何在c# NPOI中导入导出图片的攻略，希望能对你有所帮助！

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