Thumbnails for Nexus files

Thumbnails that a file browser (or even a web browser) can use to render a Nexus file shall be stored in an instance of NXnote directly below NXentry

entry:NXentry
  thumbnail:NXnote
    data:NX_BINARY
    type:NX_CHAR
    description:NX_CHAR

The data field contains the binary data of the thumbail image. The image type is determined by the type field. We currently recommend the image to be stored as PNG. The description field can be used to store provenance data which may show up as a tool-tip when the mouse pointer hovers over the files icon.

Topics for discussion

• should it go to NXroot or NXentry?

• restrict the image type to PNG or leave this open?

• shall we restrict the size of the thumbnail image?

Windows for instance uses 96x96 jpeg images.

Update 01/2015

This topic was discussed at NIAC 2014. As a directory may contain thousands of files, there are performance issues to be solved here. It was deemed to slow to open each file and extract the thumbnail from a NXnote. There are ideas to embed the thumbnail in the HDF5 file at a low level. Some experimentation is needed before this can be resolved.