Steps for converting a full scan to individual images

For my own reference, obviously. Anybody should be able to manage this, I just want to keep the method around in case I forget.

• Scan at 150dpi. Batch non-color cards together and save as greyscale.
• Load image in Gimp
• Select | By Color...
  • Fuzziness Threshold: 24.6
  • Pick a big white spot
• Floodfill: White
• Select | None
• For each card:
• If rotation is necessary:
  • Select an area with a 25% mat around edges
  • Tools | Transform Tools | Transform
  • Rotate preview matrix to align with one of the visible borders of card
  • Negate sign of rotation angle
• Crop s.t. no border is visible
• Image | Scale Image
  • New Width: 200
  • New Height s.b. between 230 and 250. If not, rescan.
• Filters | Enhance | Unsharp Mask
• Image | Mode | Greyscale or Indexed
• Save as: [date][description].png
• Undo to full sheet