Scanning Record Sleeves

A CD Rippin’ Cupboard with an A3 Scanner

In the continuing story of bits and pieces related to my music playing Emacs@Home installation, here’s the sleeve scanning function.  It’s basically just a tiny data base of common CD/LP/tape sleeve sizes. There’s a lot of sizes, unfortunately.

But what I really wanted to have was something that could detect the image area automatically.  Why doesn’t that exist?  I mean, I couldn’t find it when I googled for it half a decade ago, so it can’t possibly exist now.

It should be pretty easy to detect the image area, you’d think.  Record sleeves are usually kinda square.  So you could use…  rectangle detection…  to find the image. On the other hand, I have CD sleeves that aren’t rectangular.  And I have sleeves that have a square border, and then blackness outside the border, so just detecting the square might over-crop stuff.

I thought about using green screen techniques.  If I painted the inside cover of the scanner cover a particular green colour, then I could probably whip up a technique to…  do something.  But I fear that there’d be colour leakage, with the reflected green light giving off a green tinge to paper sleeves that aren’t very thick.

So, I don’t know.  The result is that sleeves that are half a millimeter larger than the standard sizes I have tend to be slightly over-cropped.  It’s annoying, but not annoying enough that I ever bother to re-scan the offending sleeves.  And hand-editing a scan — you know, in Gimp or something — is so ridiculous that I have to laugh.  Just see:  “Ha ha.”

The ignomity of it all.

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