image_processing: VipsForeignLoad: "/tmp/ActiveStorage-28657-20220112-4-8e2faa.jpg" is not a known file format

Why would an ActiveStorage::Blob.download return "" Does this means the file was not uploaded?

This is how the blob record looks like

#<ActiveStorage::Blob:0x00007fcffec70170
 id: 9175,
 key: "cyrlrcoiotkfyzhn923dz1elpm",
 filename: "Image.jpeg",
 content_type: "image/jpeg",
 metadata: {"identified"=>true, "analyzed"=>true},
 service_name: "amazon",
 byte_size: 0,
 checksum: "1B2M2Y8AsgTpgAmhCfg==",
 created_at: Tue, 20 Sep 2022 00:42:27.524396000 UTC +00:00>

When you try to read the same file with vips you get this issue.

 photos.first.blob.open do |file|
   Vips::Image.new_from_file file.path
 end

Error:

/Users/gathuku/.asdf/installs/ruby/3.0.3/lib/ruby/gems/3.0.0/gems/ruby-vips-2.1.4/lib/vips/image.rb:281:in `new_from_file': VipsForeignLoad: "/var/folders/ch/8_2mrh555z9_19b8lzgkf44c0000gp/T/ActiveStorage-9175-20220926-91104-3ubaml.jpeg" is not a known file format (Vips::Error)

Yes, that’s expected behaviour. I think we used to special-case zero length files and have a different error message, but we removed it for simplicity.

Would you prefer a special message for this?

For those who land on this issue looking for a solution:

Easiest option is to install libvips-dev so that it installs all the require dependancies. This will install all the required libraries to support all the major file formats.

$ sudo apt-get install libvips-dev

If you are building libvips from source you need to install the optional dependancies yourself before you install libvips. You will see in libvips install instructions that it has many optional dependancies: https://www.libvips.org/install.html.

Pick the libraries required for the file formats you want to support or almost all of them with the following before you try to build from source. The following will install support for all major formats.

$ sudo apt-get install libjpeg-turbo8-dev \
                     libexif-dev \
                     libgif-dev \
                     librsvg2-dev \
                     libpoppler-glib-dev \
                     libtiff-dev \
                     libfftw3-dev \
                     libpng-dev \
                     liborc-0.4-dev \
                     libcfitsio-dev \
                     libwebp-dev \
                     libnifti-dev \
                     libheif-dev \
                     libopenslide-dev \
                     libgsf-1-dev \
                     libopenexr-dev \
                     libmatio-dev \
                     libmagickcore-dev \
                     libmagickwand-dev \
                     libimagequant-dev

@janko Here is a sample app: https://github.com/tsrivishnu/tmp-rails-libvips-jpg-failures that you can run in docker. The README has the instructions to run it in Docker. Make sure you adapt the Dockerfile as in the first point under Setup. Let me know if you are able to reproduce it.