XSLT:将 base64 数据转换为图像文件

问题描述

我已经看到几个关于如何在 base64 中对图像文件进行编码的问题，但反过来如何 - 如何从存储在 XML 文件中的 base64 字符串重建图片?

I have seen several questions on how to encode an image file in base64, but how about the other way around - how do I reconstitute a picture from a base64 string stored in an XML file?

<resource>
<data encoding="base64">
R0lGODlhEAAQAPMAMcDAwP/crv/erbigfVdLOyslHQAAAAECAwECAwECAwECAwECAwECAwECAwEC
AwECAyH/C01TT0ZGSUNFOS4wGAAAAAxtc09QTVNPRkZJQ0U5LjAHgfNAGQAh/wtNU09GRklDRTku
MBUAAAAJcEhZcwAACxMAAAsTAQCanBgAIf8LTVNPRkZJQ0U5LjATAAAAB3RJTUUH1AkWBTYSQXe8
fQAh+QQBAAAAACwAAAAAEAAQAAADSQhgpv7OlDGYstCIMqsZAXYJJEdRQRWRrHk2I9t28CLfX63d
ZEXovJ7htwr6dIQB7/hgJGXMzFApOBYgl6n1il0Mv5xuhBEGJAAAOw==
</data>
<mime>image/gif</mime>
<resource-attributes>
    <file-name>clip_image001.gif</file-name>
</resource-attributes>
</resource>

给定上述 XML 节点 resource，我该如何创建 clip_image001.gif?

Given the above XML node resource, how do I go about creating clip_image001.gif?

请提出建议:

1. XSLT 处理器和/或扩展支持这一点，另外
2. 一个示例 XSLT，它触发转化

请注意，它必须至少能够处理 GIF &PNG 文件格式.最好不限于任何操作系统.

Note that it must be able to handle at least GIF & PNG file formats. Preferably not restricted to any OS.

基于Mads Hansen 的解决方案.主要区别在于我直接在我的命名空间中引用了 net.sf.saxon.value.Base64BinaryValue 而不是使用 saxon 命名空间，因为我比Saxonica 网站对 base64Binary-to-octets 和 base64Binary 函数的描述.

Based around Mads Hansen's solution. Main difference being that I referenced net.sf.saxon.value.Base64BinaryValue directly in my namespace rather than using the saxon namespace, because I understood the Java APIs more intuitively than the Saxonica website's descriptions of the base64Binary-to-octets and base64Binary functions.

<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:b64="net.sf.saxon.value.Base64BinaryValue"
    xmlns:fos="java.io.FileOutputStream"
    ...
    exclude-result-prefixes="b64 fos">
...
<xsl:for-each select="resource">
    <xsl:variable name="b64" select="b64:new(string(data))"/>
    ...
    <xsl:variable name="fos" select="fos:new(string($img))"/>
    <xsl:value-of select="fos:write($fos, b64:getBinaryValue($b64))"/>
    <xsl:value-of select="fos:close($fos)"/>
</xsl:for-each>
...

附言请参阅兄弟问题，了解我如何获取识别图像文件所需的哈希值.

P.S. See sibling question for my implementation of how to obtain the hashes necessary to identify the image files.

---

这个问题是我之前问过的另一个问题的子问题.

推荐答案

我从 XSL 主要列表 中找到了这个条目，它描述了如何使用 Saxon 扩展函数 xs:base64Binary-to-octet 将其流式传输到在 XSLT 2.0 样式表中使用 Java FileOutputStream 的文件:

I found this entry from the XSL maiing lists that describes how to use the Saxon extension function xs:base64Binary-to-octet to stream it out to a file using the Java FileOutputStream in an XSLT 2.0 stylesheet:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
version="2.0" xmlns:xs="http://www.w3.org/2001/XMLSchema";
xmlns:saxon="http://saxon.sf.net/";
xmlns:fos="java.io.FileOutputStream">
<xsl:template match="/">
   <xsl:variable name="img" select="concat('c:	estjesper', '.jpg')"/>
   <xsl:variable name="fos" select="fos:new(string($img))"/>
   <xsl:value-of select="fos:write($fos,
saxon:base64Binary-to-octets(xs:base64Binary(my-base64-encoded-image)))"/>
   <xsl:value-of select="fos:close($fos)"/>
</xsl:template>
</xsl:stylesheet>

这篇关于XSLT:将 base64 数据转换为图像文件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！