Find out the extension of an image, if that image doesn't have any extension

Question

Our project has an image uploading module using Java. While uploading image, if a user uploads an image with an extension of jpg/jpeg/gif/png etc., whatever the extension, we save it with same extension by changing just its name.

But here is one small issue. Suppose the user removes the extension of that image manually (of course it never happens, but let's consider it as example) and uploaded the file, it doesn't have any extension.

Is there any way to find out extension/format after reading that image (like after reading the image using getBufferedImage())?

Here I can't use mimeType as we are taking mime type from user while uploading image itself. The user may upload image without an extension, by selecting the mimeType as "image/jpeg".

See this question/answer: http://stackoverflow.com/questions/51438/getting-a-files-mime-type-in-java — Keith, Jun 27 '13 at 11:57
You can identify most file types by checking the magic number: https://en.wikipedia.org/wiki/Magic_number_(programming) — Durandal, Jun 27 '13 at 12:04
Look to iterate the readers returned from [`ImageIO.getImageReaders(Object)`](http://docs.oracle.com/javase/7/docs/api/javax/imageio/ImageIO.html#getImageReaders%28java.lang.Object%29). — Andrew Thompson, Jun 27 '13 at 13:26

score 1 · Answer 1 · answered Jun 27 '13 at 12:27

1

There are java libraries like mime-util or jmimemagic that can detect the file type from the pure content.

answered Jun 27 '13 at 12:27

Uwe Plonus

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Find out the extension of an image, if that image doesn't have any extension

1 Answers1