Java：如何在 Excel 单元格中将图像居中？

Question

我想将图像集放在excel单元格的中心，我使用XSSFClientAnchor来锚定图片位置，但仍然无法像图1那样工作。

如何将图像设置在单元格的中心，如图2所示。

InputStream iStream = new FileInputStream(iList.get(q.getProductID()));
byte[] bytes = IOUtils.toByteArray(iStream);
int pictureIdx = wb.addPicture(bytes, Workbook.PICTURE_TYPE_PNG);
XSSFDrawing patriarch = sheet.createDrawingPatriarch();
XSSFClientAnchor anchor = new XSSFClientAnchor();
anchor.setCol1(1);
anchor.setRow1(row);
anchor.setCol2(2);
anchor.setRow2(row + 1);
Picture pic = patriarch.createPicture(anchor, pictureIdx);
pic.resize();

Answer 1

图像不是单元格内容，而是悬停在工作表上称为绘图的单独层中。它们固定在细胞上。AClientAnchor提供以下设置：

col1= 图片左边缘锚定的列索引。因此图片的左边缘锚定在 的左列边缘上col1。

dx1= x 方向的差异。col1因此图片的左边缘锚定在+的左列边缘上dx1。

row1= 图片顶部边缘锚定的行索引。因此图片的上边缘锚定在 的顶行边缘上row1。

dy1= y 方向的差异。因此图片的上边缘锚定在row1+的顶行边缘上dy1。

col2= 图片右边缘锚定的列索引。因此图片的右边缘锚定在 的左列边缘上col2。

dx2= x 方向的差异。col1因此图片的右边缘锚定在+的左列边缘上dx2。

row2= 图片底部边缘锚定的行索引。因此图片的底部边缘锚定在 的顶行边缘上row2。

dy2= y 方向的差异。因此图片的底部边缘锚定在row2+的顶行边缘上dy2。

因此，给定一个完整的两个单元锚点，这决定了图片的位置及其大小。

如果图片的大小是其原始大小，则只需要一个单元格锚点。其中col1+dx1和row1+dy1决定了图片左上角的位置。尺寸由图片的原始尺寸给出。

如果仅设置col1和而不设置和，则图片的左上边缘始终锚定到 的左边缘和上边缘。因此，如果需要以单元格为中心，则需要计算 和。为了计算 ， 需要知道图片的宽度和高度以及单元格的宽度和高度。听起来很简单，但单元格的宽度和高度有多种不同的测量单位，并且二进制( ) 文件系统和( ) 文件系统之间存在很大差异。row1dx1dy1col1row1dx1dy1dx1dy1BIFF*.xlsOffice Open XML*.xlsx

以下代码提供了putPictureCentered将图片放入锚定到colIdx和给定单元格的工作表绘图中的方法rowIdx。如果可能，它会进行计算dx1，dy1以便将图片锚定在单元格的中心。它使用像素作为通用测量单位。它考虑了二进制BIFF( *.xls) 文件系统和Office Open XML( *.xlsx) 文件系统之间的差异。所以它适用于Sheet, 可能是XSSFSheet或HSSFSheet。

import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.*;

import org.apache.poi.util.IOUtils;
import org.apache.poi.util.Units;

import java.io.InputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

class CenterImageOverCell {

 static void putPictureCentered(Sheet sheet, String picturePath, int pictureType, int colIdx, int rowIdx) throws Exception {
  Workbook wb = sheet.getWorkbook();

  //load the picture
  InputStream inputStream = new FileInputStream(picturePath);
  byte[] bytes = IOUtils.toByteArray(inputStream);
  int pictureIdx = wb.addPicture(bytes, pictureType);
  inputStream.close();

  //create an anchor with upper left cell colIdx/rowIdx, only one cell anchor since bottom right depends on resizing
  CreationHelper helper = wb.getCreationHelper();
  ClientAnchor anchor = helper.createClientAnchor();
  anchor.setCol1(colIdx);
  anchor.setRow1(rowIdx);

  //create a picture anchored to colIdx and rowIdx
  Drawing drawing = sheet.createDrawingPatriarch();
  Picture pict = drawing.createPicture(anchor, pictureIdx);

  //get the picture width in px
  int pictWidthPx = pict.getImageDimension().width;
  //get the picture height in px
  int pictHeightPx = pict.getImageDimension().height;

  //get column width of column in px
  float columnWidthPx = sheet.getColumnWidthInPixels(colIdx);

  //get the height of row in px
  Row row = sheet.getRow(rowIdx);
  float rowHeightPt = row.getHeightInPoints();
  float rowHeightPx = rowHeightPt * Units.PIXEL_DPI / Units.POINT_DPI;

  //is horizontal centering possible?
  if (pictWidthPx <= columnWidthPx) {

   //calculate the horizontal center position
   int horCenterPosPx = Math.round(columnWidthPx/2f - pictWidthPx/2f);
   //set the horizontal center position as Dx1 of anchor
   if (wb instanceof XSSFWorkbook) {
    anchor.setDx1(horCenterPosPx * Units.EMU_PER_PIXEL); //in unit EMU for XSSF
   } else if (wb instanceof HSSFWorkbook) {
    //see /sf/ask/3399704241/#48607117 for HSSF
    int DEFAULT_COL_WIDTH = 10 * 256;
    anchor.setDx1(Math.round(horCenterPosPx * Units.DEFAULT_CHARACTER_WIDTH / 256f * 14.75f * DEFAULT_COL_WIDTH / columnWidthPx));
   }

  } else {
   System.out.println("Picture is too width. Horizontal centering is not possible.");
   //TODO: Log instead of System.out.println
  }

  //is vertical centering possible?
  if (pictHeightPx <= rowHeightPx) {

   //calculate the vertical center position
   int vertCenterPosPx = Math.round(rowHeightPx/2f - pictHeightPx/2f);
   //set the vertical center position as Dy1 of anchor
   if (wb instanceof XSSFWorkbook) {
    anchor.setDy1(Math.round(vertCenterPosPx * Units.EMU_PER_PIXEL)); //in unit EMU for XSSF
   } else if (wb instanceof HSSFWorkbook) {
    //see /sf/ask/3399704241/#48607117 for HSSF
    float DEFAULT_ROW_HEIGHT = 12.75f;
    anchor.setDy1(Math.round(vertCenterPosPx * Units.PIXEL_DPI / Units.POINT_DPI * 14.75f * DEFAULT_ROW_HEIGHT / rowHeightPx));
   }

  } else {
   System.out.println("Picture is too height. Vertical centering is not possible.");
   //TODO: Log instead of System.out.println
  }

  //resize the picture to it's native size
  pict.resize();

 }

 public static void main(String[] args) throws Exception {

  //Workbook wb = new HSSFWorkbook(); String resultName = "CenterImageTest.xls";
  Workbook wb = new XSSFWorkbook(); String resultName = "CenterImageTest.xlsx";
  Sheet sheet = wb.createSheet("Sheet1");

  int colIdx = 1;
  int colWidth = 20; //in default character widths
  int rowIdx = 1;
  float rowHeight = 100; //in points

  //========================prepare sheet
  //create cell
  Row row = sheet.createRow(rowIdx);
  Cell cell = row.createCell(colIdx);
  //set column width of colIdx in default character widths
  sheet.setColumnWidth(colIdx, colWidth * 256);
  //set row height of rowIdx in points
  row.setHeightInPoints(rowHeight);
  //========================end prepare sheet

  //put image centered
  String picturePath = "./pict100x100.png"; // small image
  //String picturePath = "./pict100x200.png"; // image too height
  //String picturePath = "./pict200x100.png"; // image too width
  //String picturePath = "./pict200x200.png"; // image too big
  putPictureCentered(sheet, picturePath, Workbook.PICTURE_TYPE_PNG, colIdx, rowIdx);

  FileOutputStream fileOut = new FileOutputStream("./" + resultName);
  wb.write(fileOut);
  fileOut.close();
  wb.close();

 }
}