jpeg的有效base64字符串

这是jpeg的有效base64字符串吗？

data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAMCAgICAgMCAgIDAwMDBAYEBAQEBAgGBgUGCQgKCgkICQkKDA8MCgsOCwkJDRENDg8QEBEQCgwSExIQEw8QEBD/2wBDAQMDAwQDBAgEBAgQCwkLEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBD

所讨论的字符是“ base64”之后的“ / 9j /”，

我猜这可能与压缩有关，因为它是JPEG。

正如与png的base64字符串相比时，模式是不同的，即字符模式与上面的不同。

 data:image/png;base64,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

我的问题的根源是我将base64画布数组编码为.jpeg和.png--.png的输出很好，而.jpeg的总是输出为黑盒。

我正在使用html2canvas（javascript）捕获图像，它们是html节点的“图像”，我一直在解决透明度问题，例如将dom节点的背景设置为白色。

我正在编码的所有jpeg图像都具有这种“ / 9j /”模式，我在循环中生成它们，因此它很可能是所有图像都具有的共同属性。

我似乎也找不到网上一种不错的工具来验证base64字符串。

让我们检查：

$ echo -n '/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAMCAgICAgMCAgID' | base64 --decode | file -
/dev/stdin: JPEG image data, JFIF standard 1.01

因此，它被认为是有效的JPEG标头（​​不过，这不一定意味着整个JPEG数据都是有效的，但至少看起来像是JPEG）。

JPEG数据和PNG数据之间的差异是因为文件格式不同。此外，/在Base64中也是有效字符。