wkhtmltopdf每次运行都会生成不同的校验和 [英] wkhtmltopdf generates a different checksum on every run
问题描述
我试图验证从wkhtmltopdf生成的内容在运行之间是相同的，但是，每次运行wkhtmltopdf时，我都会在同一页面上获得不同的哈希/校验和值.我们正在谈论一些真正的基础知识，例如使用html页面:
I'm trying to verify that the content generated from wkhtmltopdf is the same from run to run, however every time I run wkhtmltopdf I get a different hash / checksum value against the same page. We are talking something real basic like using an html page of:
<html>
<body>
<p> This is some text</p>
</body
</html>
每次运行wkhtmltopdf时，我都会得到一个不同的md5或sha256哈希，它使用以下惊人的一行:
I get a different md5 or sha256 hash every time I run wkhtmltopdf using an amazing line of:
./wkhtmltopdf example.html ~/Documents/a.pdf
并使用以下python哈希器:
And using a python hasher of:
def shasum(filename):
sha = hashlib.sha256()
with open(filename,'rb') as f:
for chunk in iter(lambda: f.read(128*sha.block_size), b''):
sha.update(chunk)
return sha.hexdigest()
或仅将sha256与md5交换的md5版本
or the md5 version which just swaps sha256 with md5
为什么wkhtmltopdf会生成足以引起不同校验和的不同文件，并且有什么方法可以做到这一点?可以通过传递一些命令行来防止这种情况?
Why would wkhtmltopdf generate a different file enough to cause a different checksum, and is there any way to not do that? some command line that can be passed in to prevent this?
我尝试了--default-header，-no-pdf-compression和--disable-smart-shrinking
I've tried --default-header, --no-pdf-compression and --disable-smart-shrinking
这是在MAC osx上，但是我已经在其他计算机上生成了这些pdf，并以相同的结果下载了它们.
This is on a MAC osx but I've generated these pdf's on other machines and downloaded them with the same result.
wkhtmltopdf版本= 0.10.0 rc2
wkhtmltopdf version = 0.10.0 rc2
推荐答案
我尝试了此操作，并在emacs中打开了生成的PDF. wkhtmltopdf在PDF中嵌入了"/CreationDate"字段.每次运行都会有所不同，并且会破坏两次运行之间的哈希值.
I tried this and opened the resulting PDF in emacs. wkhtmltopdf is embedding a "/CreationDate" field in the PDF. It will be different for every run, and will screw up the hash values between runs.
我没有看到禁用"/CreationDate"字段的选项，但是在计算哈希值之前将其从文件中删除很简单.
I didn't see an option to disable the "/CreationDate" field, but it would be simple to strip it out of the file before computing the hash.
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