问题
Is there a bullet proof way to detect MIME type of uploaded file in Ruby or Ruby on Rails? I'm uploading JPEGs and PNGs using SWFupload and content_type
is always "application/octet-stream"
回答1:
The ruby-filemagic gem will do it:
require 'filemagic'
puts FileMagic.new(FileMagic::MAGIC_MIME).file(__FILE__)
# => text/x-ruby; charset=us-ascii
This gem does not look at the file extension at all. It reads a bit of the file contents and uses that to guess the file's type.
回答2:
In Ruby on Rails you can do:
MIME::Types.type_for("filename.gif").first.content_type # => "image/gif"
回答3:
You can use this reliable method base on the magic header of the file :
def get_image_extension(local_file_path)
png = Regexp.new("\x89PNG".force_encoding("binary"))
jpg = Regexp.new("\xff\xd8\xff\xe0\x00\x10JFIF".force_encoding("binary"))
jpg2 = Regexp.new("\xff\xd8\xff\xe1(.*){2}Exif".force_encoding("binary"))
case IO.read(local_file_path, 10)
when /^GIF8/
'gif'
when /^#{png}/
'png'
when /^#{jpg}/
'jpg'
when /^#{jpg2}/
'jpg'
else
mime_type = `file #{local_file_path} --mime-type`.gsub("\n", '') # Works on linux and mac
raise UnprocessableEntity, "unknown file type" if !mime_type
mime_type.split(':')[1].split('/')[1].gsub('x-', '').gsub(/jpeg/, 'jpg').gsub(/text/, 'txt').gsub(/x-/, '')
end
end
回答4:
The ruby-filemagic gem is good solution, but requires additional dependencies on libmagic (recently removed from CarrierWave as part of CarrierWave::MagicMimeTypes removal).
If you're interested in a pure ruby implementation, consider the MimeMagic gem! It works well for file types listed in the freedesktop.org mime database:
require 'mimemagic'
MimeMagic.by_magic(File.open('Table-Flip-Guy.jpg')).type # => "image/jpeg"
For Microsoft Office 2007+ formats (xlsx, docx, and pptx), require the overlay (unless you're okay with the generic "application/zip" MIME type for these files)
require 'mimemagic'
require 'mimemagic/overlay'
MimeMagic.by_magic(File.open('big_spreadsheet.xlsx')).type # => "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
回答5:
filemagic gem is good solution but depends lots of unnecessary gems. (rails, aws-sdk-core, ...)
If your app is small and only runs in Linux or OSX, consider to use file
program:
require 'shellwords'
mimetype = `file --brief --mime-type - < #{Shellwords.shellescape(__FILE__)}`.strip
Note: Replace __FILE__
with any expr contains the filepath.
回答6:
mimemagic gem will also do it
https://github.com/minad/mimemagic
from the oficial documentation
MimeMagic is a library to detect the mime type of a file by extension or by content. It uses the mime database provided by freedesktop.org (see http://freedesktop.org/wiki/Software/shared-mime-info/).
require 'mimemagic' MimeMagic.by_extension('html').text? MimeMagic.by_extension('.html').child_of? 'text/plain' MimeMagic.by_path('filename.txt') MimeMagic.by_magic(File.open('test.html')) # etc...
回答7:
You can use
Mime::Type.lookup_by_extension(extention_name)
Thanks
来源:https://stackoverflow.com/questions/4600679/detect-mime-type-of-uploaded-file-in-ruby