相同的图像，但不同的base64

我用下面的函数创建我的Gravatar图像的base64编码字符串（https://www.gravatar.com/avatar/cd5415f97afbe0177ba35ae31fbfd0db）：相同的图像，但不同的base64

final BASE64Encoder encoder = new BASE64Encoder(); 

String encoded = encoder.encode(inputStreamToByteArray(is)); 
encoded = encoded.replaceAll("\r?\n", ""); 

return encoded;

我一个前两天跑法，得到了下面的base64编码字符串：

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

就在今天，我再次执行该方法，使用相同的图像。但是，而不是获取相同的编码字符串，我收到：

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

正如你可能会注意到，第一几个字符是相同的，但如果你看看字符串的结束，您可以直接发现他们是完全不同。这是为什么？该图像仍然是我的Gravatar图像（例如，使用http://codebeautify.org/base64-to-image-converter为两个字符串显示相同的图像）。

感谢您的任何提示，解释！我的实施有什么问题吗？一些执行时间或位置是否依赖？我怎样才能得到相同的图像base64字符串？

PS：inputStreamToByteArray被如下实现：

public static byte[] inputStreamToByteArray(final InputStream is) { 
    final ByteArrayOutputStream buffer = new ByteArrayOutputStream(); 
    final byte[] data = new byte[16384]; 

    try { 
     int nRead; 
     while ((nRead = is.read(data, 0, data.length)) != -1) { 
      buffer.write(data, 0, nRead); 
     } 
     buffer.flush(); 
    } catch (final IOException e) { 
     return null; 
    } finally { 
     try { 
      buffer.close(); 
     } catch (final IOException e) { 
      // ignore 
     } 
    } 

    return buffer.toByteArray(); 
}

来源

2016-10-04 Philipp

转换两个图像回.jpg和使用http://regex.info/exif.cgi，下面的头部注释出现：

一：

CREATOR ：GD-JPEG V1.0（使用IJG JPEG V80），质量= 90

其他：

CREATOR：GD-JPEG V1.0（使用IJG JPEG V62），质量= 90

（不记得我转换该顺序中的图像，但是有一个版本改变无论哪种方式）

正如你所看到的，他们已经升级了JPEG压缩（或规格？）到新的版本，从而导致不同的JPEG编码，或在评论中至少区别。

因此，要回答你的问题，似乎没有要与你的base64转换器的问题，但只是两个图像实际上是不同的

来源

2016-10-04 21:01:24

因此，它实际上不是同一个JPEG文件，然后...相同的图片，不同的编码......这引发了谁对重新编码它的问题？ Web服务器是否习惯于在将jpegs发送给客户端以标准化质量或类似内容时对其进行重新编码？ – BenPen

是的。通常，服务于静态图像的服务器将调整并优化原始图像，同时缓存结果。 – Phil

那么Gravatar是否会更改版本（例如，每天）以使比较更加困难？或者JPEG版本是如何改变的？ – Philipp

相同的图像，但不同的base64

回答

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