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How to select a difference of two layers?


Question

Consider the following two files.

Background:

background

Background with some content on top:

content

How do I get a flat image that is content-background? ie. the result should be white text with the blood stains on a transparent background.

The underlying issue that I am trying to solve:

The layers "Layer 27 copy 3" and "Layer 55" (the blood stains) use "multiply" blending mode, therefore simply merging these with the text will result in:

enter image description here

2013/08/20
1
3
8/20/2013 1:48:00 PM

  1. Turn off visibility for paragraph layer ("Each correct answer will...")
  2. New Layer above all other layers (Command/Ctrl-Option/Alt-Shift-N)
  3. Merge Visible (Command/Ctrl-Option/Alt-Shift-E)
  4. Turn off visibility for all other layers
  5. Select all (Command/Ctl-a)
  6. Copy (Command/Ctrl-c)
  7. Add Layer Mask
  8. Select Layer Mask (Command/Ctrl-)
  9. Paste (Command/Ctrl-v)
  10. Adjust levels to bring up the white nad red and reduce the black.
    levels
  11. Turn on visibility fo the paragraph layer ("Each Correct Answer will...")
  12. Save for web

book final

To retain all the blood - on or off text

  1. Set both the blood layers to Normal.
  2. Remove the mask on the one layer.
  3. Merge the two layers
  4. Choose Select > Color Range and click a white area of the layer
  5. Hit OK
  6. Inverse Selection (Select > Inverse)
  7. Add layer mask
  8. Set layer to multiply.

This leaves you with this...
(grey background used to show transparency)

book3

You can then further mask the blood if you'd like.

2012/09/24
1
9/24/2012 1:17:00 AM