Getting cell witdth and height from excel with Apache POI

cell height and width are defined on row and column. The problem is that metods HSSFSheet.getColumnWidth()  and HSSFRow.getHeight() returns value in points.

 So i writed class witch do the math to calculate points to pixel.  :]

public class PixelUtil {
    public static final short EXCEL_COLUMN_WIDTH_FACTOR = 256;
    public static final short EXCEL_ROW_HEIGHT_FACTOR = 20;
    public static final int UNIT_OFFSET_LENGTH = 7;
    public static final int[] UNIT_OFFSET_MAP = new int[] { 0, 36, 73, 109, 146, 182, 219 };
   
    public static short pixel2WidthUnits(int pxs) {
        short widthUnits = (short) (EXCEL_COLUMN_WIDTH_FACTOR * (pxs / UNIT_OFFSET_LENGTH));
        widthUnits += UNIT_OFFSET_MAP[(pxs % UNIT_OFFSET_LENGTH)]; 
        return widthUnits;
    }
    public static int widthUnits2Pixel(short widthUnits) {
        int pixels = (widthUnits / EXCEL_COLUMN_WIDTH_FACTOR) * UNIT_OFFSET_LENGTH;
        int offsetWidthUnits = widthUnits % EXCEL_COLUMN_WIDTH_FACTOR;
        pixels += Math.floor((float) offsetWidthUnits / ((float) EXCEL_COLUMN_WIDTH_FACTOR / UNIT_OFFSET_LENGTH));  
        return pixels;
    }
    public static int heightUnits2Pixel(short heightUnits) {
        int pixels = (heightUnits / EXCEL_ROW_HEIGHT_FACTOR);
        int offsetWidthUnits = heightUnits % EXCEL_ROW_HEIGHT_FACTOR;
        pixels += Math.floor((float) offsetWidthUnits / ((float) EXCEL_ROW_HEIGHT_FACTOR / UNIT_OFFSET_LENGTH));  
        return pixels;
    }
 }

so when I want to get cell width and  height I use this to get value in pixel, values are approximatelly.

 PixelUtil.heightUnits2Pixel((short) row.getHeight())
PixelUtil.widthUnits2Pixel((short) sh.getColumnWidth(columnIndex));