POI插入图片至Excel使用固定的长宽

使用POI在Excel里插入图片，如何使插入的图片使用固定的大小？先介绍原有的两种方式：

　　一种是指定开始和结尾单元格，然后从头画到尾，相当于平铺
　　还有一种就是仅指定开始的单元格，图片的大小跟这个单元格的长宽有关，可以放大缩小固定的倍数，相当于左对齐

第一种效果如下：

第二种效果如下：

第一种方法的关键代码如下：

 private void pictureToSheet(Sheet finalSheet, Row row, Cell cell, int pictureIdx) {
     Drawing patriarch = finalSheet.createDrawingPatriarch();
     ExcelPositionRange excelPositionRange = ExcelTransferUtils.getMergedRegionPositionRange(finalSheet, row.getRowNum(), cell.getColumnIndex());
     ClientAnchor anchor = patriarch.createAnchor(0, 0, 1023, 255,
             excelPositionRange.getFirstCol(),
             excelPositionRange.getFirstRow(),
             excelPositionRange.getLastCol(),
             excelPositionRange.getLastRow()
     );
     patriarch.createPicture(anchor, pictureIdx);
 }

注：代码中的excelPositionRange，是俺自定义的一个类型。里边只有四个变量和get/set方法，四个变量分别是单元格的开始、结尾单元格的横纵坐标。这个大家可以根据需要来改。

PS：其中1023和255指的是每个单元格被切分的份数，指定的是最后的单元格的最右下角的一个点，其方法的源代码在本文最后的附录里。

第二种方法的关键代码如下：

 private void pictureToSheet(Sheet finalSheet, Row row, Cell cell, int pictureIdx) {
     Drawing patriarch = finalSheet.createDrawingPatriarch();
     ExcelPositionRange excelPositionRange = ExcelTransferUtils.getMergedRegionPositionRange(finalSheet, row.getRowNum(), cell.getColumnIndex());
 
     CreationHelper helper = finalSheet.getWorkbook().getCreationHelper();
     ClientAnchor anchor = helper.createClientAnchor();
 
     // 图片插入坐标
     anchor.setCol1(excelPositionRange.getFirstCol());
     anchor.setRow1(excelPositionRange.getFirstRow());
 
     // 使用固定的长宽比例系数
     double a = 5.9;
     double b = 1;
 
     // 插入图片
     Picture pict = patriarch.createPicture(anchor, pictureIdx);
     pict.resize(a,b);
 }

进阶方法：
　　在第二种方法的基础上，可以计算出不同的系数，达到生成图片都是同一个长宽的功能，从而输出固定大小的图片

 private void pictureToSheet(Sheet finalSheet, Row row, Cell cell, int pictureIdx) {
     Drawing patriarch = finalSheet.createDrawingPatriarch();
     ExcelPositionRange excelPositionRange = ExcelTransferUtils.getMergedRegionPositionRange(finalSheet, row.getRowNum(), cell.getColumnIndex());
 
     CreationHelper helper = finalSheet.getWorkbook().getCreationHelper();
     ClientAnchor anchor = helper.createClientAnchor();
 
     // 图片插入坐标
     anchor.setCol1(excelPositionRange.getFirstCol());
     anchor.setRow1(excelPositionRange.getFirstRow());
 
     // 指定我想要的长宽
     double standardWidth = 112;
     double standardHeight = 41;
 
     // 计算单元格的长宽
     double cellWidth = finalSheet.getColumnWidthInPixels(cell.getColumnIndex());
     double cellHeight = cell.getRow().getHeightInPoints()/72*96;
 
     // 计算需要的长宽比例的系数
     double a = standardWidth / cellWidth;
     double b = standardHeight / cellHeight;
 
     // 插入图片
     Picture pict = patriarch.createPicture(anchor, pictureIdx);
     pict.resize(a,b);
 }

PS：这里参考了POI获取单元格长宽的的方法：http://www.cnblogs.com/acm-bingzi/p/poiWidth.html

附录一
　　一般插入图片的样例代码：

 // 插入 PNG 图片至 Excel
 String fileName = strAppRootPath + "images/" + "bxlogo.png";
 
 InputStream is = new FileInputStream(fileName);
 byte[] bytes = IOUtils.toByteArray(is);
 
 int pictureIdx = workbook.addPicture(bytes, Workbook.PICTURE_TYPE_PNG);
 
 CreationHelper helper = workbook.getCreationHelper();
 Drawing drawing = sheet.createDrawingPatriarch();
 ClientAnchor anchor = helper.createClientAnchor();
 
 // 图片插入坐标
 anchor.setCol1(0);
 anchor.setRow1(1);
 // 插入图片
 Picture pict = drawing.createPicture(anchor, pictureIdx);
 pict.resize();

附录二
　　patriarch.createAnchor的源代码跟踪

 /**
  * Creates a new client anchor and sets the top-left and bottom-right
  * coordinates of the anchor.
  *
  * Note: Microsoft Excel seems to sometimes disallow
  * higher y1 than y2 or higher x1 than x2, you might need to
  * reverse them and draw shapes vertically or horizontally flipped!
  *
  * @param dx1  the x coordinate within the first cell.
  * @param dy1  the y coordinate within the first cell.
  * @param dx2  the x coordinate within the second cell.
  * @param dy2  the y coordinate within the second cell.
  * @param col1 the column (0 based) of the first cell.
  * @param row1 the row (0 based) of the first cell.
  * @param col2 the column (0 based) of the second cell.
  * @param row2 the row (0 based) of the second cell.
  */
 public HSSFClientAnchor(int dx1, int dy1, int dx2, int dy2, short col1, int row1, short col2, int row2) {
     super(dx1, dy1, dx2, dy2);
 
     checkRange(dx1, 0, 1023, "dx1");
     checkRange(dx2, 0, 1023, "dx2");
     checkRange(dy1, 0, 255, "dy1");
     checkRange(dy2, 0, 255, "dy2");
     checkRange(col1, 0, MAX_COL, "col1");
     checkRange(col2, 0, MAX_COL, "col2");
     checkRange(row1, 0, MAX_ROW, "row1");
     checkRange(row2, 0, MAX_ROW, "row2");
 
     setCol1((short) Math.min(col1, col2));
     setCol2((short) Math.max(col1, col2));
     setRow1(Math.min(row1, row2));
     setRow2(Math.max(row1, row2));
 
     if (col1 > col2){
         _isHorizontallyFlipped = true;
     }
     if (row1 > row2){
         _isVerticallyFlipped = true;
     }
 }

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