ireport 关于背景图片的奇怪问题！不知道有人知道吗？【有图片】有原码

就是很简单的,其他都为空，然后设置一个background，background引用一个图片，然后想这个图片作为水印！结果发现图片并不能覆盖整个页面，另外是否必须把上下左右的留空都变为0，背景图片才可以覆盖整个页面。能否留空依然留空，通过某种设置背景图片仍然能够覆盖整个页面包括留空的地方。代码如下：注：曾经设置过居中也没有用啊！
<?xml version="1.0" encoding="UTF-8"  ?>
<!-- Created with iReport - A designer for JasperReports -->
<!DOCTYPE jasperReport PUBLIC "//JasperReports//DTD Report Design//EN" "http://jasperreports.sourceforge.net/dtds/jasperreport.dtd">
<jasperReport
         name="Untitled_report_1"
         columnCount="1"
         printOrder="Vertical"
         orientation="Portrait"
         pageWidth="595"
         pageHeight="842"
         columnWidth="535"
         columnSpacing="0"
         leftMargin="0"
         rightMargin="0"
         topMargin="0"
         bottomMargin="0"
         whenNoDataType="NoPages"
         isTitleNewPage="false"
         isSummaryNewPage="false">
    <property name="ireport.scriptlethandling" value="0" />
    <property name="ireport.encoding" value="UTF-8" />
    <import value="java.util.*" />
    <import value="net.sf.jasperreports.engine.*" />
    <import value="net.sf.jasperreports.engine.data.*" />
        <background>
            <band height="842"  isSplitAllowed="true" >
                <image evaluationTime="Now" hyperlinkType="None"  hyperlinkTarget="Self" >
                    <reportElement
                        x="0"
                        y="0"
                        width="595"
                        height="842"
                        key="image-1"/>
                    <box></box>
                    <graphicElement stretchType="NoStretch"/>
                    <imageExpression class="java.lang.String"><![CDATA["D:\\DOC\\My Pictures\\04B928934CD6F40DA37E71B4BD973FAE.jpg"]]></imageExpression>
                </image>
            </band>
        </background>
        <title>
            <band height="50"  isSplitAllowed="true" >
            </band>
        </title>
        <pageHeader>
            <band height="50"  isSplitAllowed="true" >
            </band>
        </pageHeader>
        <columnHeader>
            <band height="30"  isSplitAllowed="true" >
            </band>
        </columnHeader>
        <detail>
            <band height="100"  isSplitAllowed="true" >
            </band>
        </detail>
        <columnFooter>
            <band height="30"  isSplitAllowed="true" >
            </band>
        </columnFooter>
        <pageFooter>
            <band height="50"  isSplitAllowed="true" >
            </band>
        </pageFooter>
        <lastPageFooter>
            <band height="50"  isSplitAllowed="true" >
            </band>
        </lastPageFooter>
        <summary>
            <band height="50"  isSplitAllowed="true" >
            </band>
        </summary>
</jasperReport>
如图片所示：背景图片居中上边下边均有很多留空啊