I would like to display the DPI and color mode (RGB/CMYK) for JPEG images, is it possible to write a plugin to add more info in Finder's Preview Pane?

Is there an API for developers to do so?

  • 1
    The best place to look would be Apple's Developer Site – Allan May 16 '17 at 2:56
  • thanks, but the document is quite vague about the capability regarding extending Finder functionalities. I noticed there is a list of NSExtensionPointIdentifier extension point identifiers, the closest one in Finder Sync, which is still not the one I'm looking for. Can you share me more lights? – Raptor May 16 '17 at 3:00
  • A jpg doesn't have a DPI, btw. Nothing has or needs a DPI until you are going to print it; all it has is 'dimensions', pixel count. – Tetsujin May 16 '17 at 7:19
  • Yes, I come up with this question as I have to check the JPEG is ready for printing or not ( i.e. > 300 DPI ) – Raptor May 17 '17 at 3:07

Probably more trouble than you want but if you open jpeg in preview and under tools menu click on 'Show Inspector' a window appears with image size, DPI, color mode (RGB) and other info. If that is too much trouble maybe you can look to see how Preview gets and displays this info.

  • I repeat... an image on a computer does not have a 'DPI'. That is only for printed output. It it an utterly meaningless figure on a computer. – Tetsujin May 16 '17 at 19:07
  • Yes I understand DPI is a printer related quantity. But the procedure I described gives a value named DPI for a jpeg image. I guess its Apple's responsibility to explain what that means for an image. I would guess they use DPI for pixels per inch even though that is not abbreviated by DPI. Maybe that is what the questioner wanted anyway. – jmh May 16 '17 at 22:21
  • Yes John & Tstsujin, I frequently require to check the DPI of the image to see whether it's fit for printing ( i.e. >300 DPI ), thus I come up with this question. – Raptor May 17 '17 at 3:06

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