Adobe Photoshop

Extracting regions with Photoshop for scientific (quantitative) analysis

If you want to extract regions with Photoshop, uncheck the Anti-aliased checkbox (available in the Polygonal Lasso Options after double-clicking on the Polygonal Lasso tool in the toolbox). Otherwise the borders of the excised regions of interest will be smoothed by anti-aliasing, a process which generates interpolated greyvalues at the border of the extracted structure!

Photoshop: Changing image type from 8 bit LUT (indexed color) to grayscale


8 bit with LUT (indexed color): If you use Image.Mode.Grayscale, Photoshop treats such an image like an RGB image: it will not simply remove the LUT, but calculate a grayvalue from the brightness of all displayed channels, therefore:

  1. From menu Image.Mode.Color Table: choose Table: Greyscale
  2. Choose Image.Mode.Grayscale

The greyscale indexed image's histogram differs slightly from the one of the grayscale image (as checked with ImageJ); Image J performs the change to 8 bit grayscale in one step.

Photoshop 7: merge channels

  1. Open the respective 8 bit grayscale images (must have identical dimensions)
  2. From th Channels palette menu, choose Merge Channels
  3. Choose Mode RGB color (for merging up to 3 channels), click OK
  4. Specify channels (assign greyscale images to RGB channels)
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