PDF文件标题序列:为什么在许多文档中使用"25 e2 e3 cf d3"位流? [英] PDF File header sequence: Why '25 e2 e3 cf d3' bits stream used in many document?
问题描述
我知道可以告知读者pdf是否包含二进制文件.
I know that inform to a reader whether the pdf contains binary or not.
但是，为什么"25 e2 e3 cf d3"不是随机二进制?因为有这么多文件.
But why "25 e2 e3 cf d3" not random binary? Because so many document has that.
是不是因为这么多人使用相同的pdf库?
Is it Just because, so many use same pdf library ?
引用:
推荐答案
在PDF中浏览我在这里看到许多PDF处理器都使用这些非常字母％âãÏÓ"的字母，其中包括Adobe产品.
Looking through the PDFs I have here it looks like a number of PDF processors use these very letters "%âãÏÓ", among them Adobe products.
并非所有这些处理器都使用相同的基本PDF库，因此无法通过类似的方式来解释使用相同的字母.
Not all of those processors use the same basic PDF library, so the use of the same letters cannot be explained by something like that.
最有可能是由于Adobe软件使用第二行注释创建了PDF.多年来，其他软件的开发人员一直使用Adobe软件产生的示例文件作为他们创建的PDF的模板.
Most likely it is due to the fact that Adobe software creates PDFs with that second line comment. For many years developers of other software used example files produced by Adobe software as templates for the PDFs they created.
是的，ISO 32000-1规范只需要
Yes, the specification ISO 32000-1 merely requires
如果PDF文件像大多数一样包含二进制数据(请参见7.2，词法约定")，则标题行应紧随其后的注释行应至少包含四个二进制字符，即，代码为128的字符或更高.
If a PDF file contains binary data, as most do (see 7.2, "Lexical Conventions"), the header line shall be immediately followed by a comment line containing at least four binary characters—that is, characters whose codes are 128 or greater.
(与早期的PDF参考文献也建议相同)，因此 无需使用相同的二进制字符 .
(and the earlier PDF references also recommend the same), so there is no need to use the same binary characters.
但是还有没有理由不使用它们 .为什么在这方面偏离了Adobe软件产生的工作示例文件?
But there also is no reason not to use them. Why deviate from the working example files produced by Adobe software in this regard?
Especially in the years before the ISO specification, when there only were the PDF references, one tended to be as Adobe-like as possible in the document structure created as the PDF references were not considered normative in nature by Adobe. Thus, if your document was valid by the references, Adobe viewers could still reject it without that counting as a bug...
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