How to determine if a file is a raster or vector eps with a script

Question

I am trying to write a script to open an EPS file in Photoshop if it is a raster image and in Illustrator if it is a vector image. The problem is how to determine that.
 
Since it is before the file is opened, I need to reference the XMP or parse the file.
For the moment, I found that it can be determined to some extent by checking whether exif:PixelXDimension exists or not.
var pixelWidth = xmpMetaObj.getProperty(XMPConst.NS_EXIF, 'PixelXDimension').toString() ;
 
What are some of the more reliable methods? The file could have been saved using a non-Adobe app.

sttk3 · Accepted Answer

@Stephen Marsh

vector_illustrator.eps is vector, all others are raster.

If the program identifies by app name, such as Photoshop or Illustrator/Affinity Photo via Creator, History, etc., the program needs to have a table of which apps indicate which.

That is not practical, so for now the exif:PixelXDimension shown at the beginning is more promising. Nevertheless, thanks for the idea.

It would be appreciated if you could remove the Exiftool output as it contains my personal information. I have already downloaded it.

In the end, I decided to adopt exif:PixelXDimension. Thank you for your response.

Peter Villevoye · Answer

Well, one problem is that most EPS files contain at least some pixel data, to serve as a proxy for the true vector data. EPS was developed for the sake of letting early software like Aldus PageMaker quickly show a rough pixel-based depiction of the image on the screen (encapsulated as a separate part in the EPS file), while parsing the vector-based Adobe PostScript part directly to a printer, without actually interpreting it (that was/is handled by the official Adobe PostScript/PDF RIP in the printer). So PageMaker could handle PostScript imagery from drawing tools like Aldus FreeHand, without the costly and slow on-screen processing of the PostScript language.That's how EPS begun. But in the 80's and 90's, developers have created dozens of use-cases of an EPS for certain reasons. An EPS with a huge bit-image and a vector-based clipping masks, a lo-res EPS to connect 4 color-separated hi-res EPS files (DCS), an EPS containing one huge bitmap and some PostScript to define 2 or more color curves (e.g. Duotones), etcetera...These have all been declared legacy (Photoshop files can hold such features natively now), but they're still around ! And in many other cases less proficient designers simply toss a bitmap image (like a logo or icon) in Adobe Illustrator, save it as an EPS or Illustrator file, hoping/thinking it becomes a vector image, and call it a day. Such an Illustrator file contains a tiny bit of PostScript (a vector rectangle, which holds a bunch of bitmap data). It probably also has been saved with "PDF complaince", meaning that it's actually wrapped as a PDF file, containing some extra AI resources (the PostScript and the bitmap), with an ".ai" extension slapped on it as the file name (so Illustrator will open it when double-clicking it...) And to make it worse: especially in an AI file, there might rightfully be a creative mix of vectors and bitmap-based parts in it. And the same can be true for a PSD file. So unless you're truly looking into the coded content of an AI, EPS, or PSD file, or simply look at it on-screen and zoom-in a lot, you never know what the file actually contains.

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