相关疑难解决方法(0)

当我提交一个附加文件的简单表格时:

<form enctype="multipart/form-data" action="http://localhost:3000/upload?upload_progress_id=12344" method="POST">
<input type="hidden" name="MAX_FILE_SIZE" value="100000" />
Choose a file to upload: <input name="uploadedfile" type="file" /><br />
<input type="submit" value="Upload File" />
</form>

它是如何在内部发送文件的？该文件是作为数据发送的HTTP主体的一部分吗？在此请求的标头中,我没有看到与文件名相关的任何内容.

我只是想知道发送文件时HTTP的内部工作原理.

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。

我有一台照相机，向我发送带有一些标签的xml文件，其中包括一个表示base64格式图像的标签。图像为JPEG格式。

出于某种原因，表示图像的标签并不总是具有相同的名称（因为相机问题）

因此，要确定地检测包含图像的标签是正确的，我现在必须做一件事：

始终以/ 9j /？开头的base64格式的JPEG图像。

范例：

data:image/jpeg;base64,-->/9j/<--4RYQRXhpZgAATU0AKgAAAAgABwESAAMAAAABAAEAAAEaAAUAAAABAAAAYgEbAAUAAAABAAAAagEoAAMAAAABAAIAAAExAAIAAAAgAAAAcgEyAAIAAAAUAAAAkodpAAQAAAABAAAAqAAAANQACvyAAAAnEAAK/IAAACcQQWRvYmUgUGhvdG9zaG9wIENTNiAoTWFjaW50b3NoKQAyMDE2OjA4OjA1IDA5OjQ1OjA4AAAAAAOgAQADAAAAAf//AACgAgAEAAAAAQAAAPGgAwAEAAAAAQAAAFkAAAAAAAAABgEDAAMAAAABAAYAAAEaAAUAAAABAAABIgEbAA....