How to Simulate Shallow Depth of Field in Gimp

Step-by-Step Guide

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   Step 1: Open your image in Gimp.

   Separate the image into RGB channels.
   
   Click on Colors >> Components >> Decompose.
   
   Examine each resultant image to see which one provides the greatest contrast.
   
   For this particular picture, the blue channel provides the greatest contract.
   
   Delete the two layers that will not be used.
   
   Lessen the amount of required work by tracing around the desired part of the image by drawing around it with the lasso tool.
   
   Invert the selection (CTRL I) and then fill in the area with black.
   
   Be sure that black is the foreground color, that FG Color Fill and Fill Whole Selection are selected.
   
   Your image should look like this. , Right click on the image and choose Colors >> Threshold.
   
   Click in the histogram and drag it towards the right.
   
   Watch as the image turns to black and white.
   
   Move the selections/controls around until you find something that looks the best to you.
   
   Click OK. ,). ,, If you don't see the Layers dialog box, click on Windows > Recently Closed Docks and reopen it. ,,, (CTRL A and CTRL C). , It will paste as a grayscale image. , By doing this, you will be able to view your image and the mask simultaneously. , The mask image is simply a guide. ,,,, Also, you will need to move around the image refining it.
   
   Periodically, turn off the visibility of your Mask Guide (click on the "eye") to view your progress. ,,,, It will be one of the layers in the Layers dialog.
   
   Then duplicate it. , Rename it "Blurred". , Experiment with the various values to get your' depths of field.
   
   What you like. ,,, In the original image window, Paste (Ctrl+V).
   
   This should paste the inverted mask into the layer mask. , If done correctly, your subject should be sharp and the background blurry.
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   Step 2: Create a layer mask of your photo.

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   Step 3: Force the outline of your chosen subject to white.

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   Step 4: Fix any last problems that you see with the image (this can get tiresome

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   Step 5: depending on the contrast that you have gotten so far.

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   Step 6: Composite the mask and the image.

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   Step 7: Create a new layer.

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   Step 8: Name the layer something definitive

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   Step 9: as in "Mask Guide".

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    Step 10: Make sure that your original image window is open.

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    Step 11: Select that image

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    Step 12: and copy it.

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    Step 13: Go back to the mask image and paste into the new layer.

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    Step 14: Anchor the pasted image and reduce the opacity of the Mask Guide to about 70%.

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    Step 15: Select the background layer in the mask image.

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    Step 16: Select a brush (probably small and a bit fuzzy) from the Brushes Dialog (CTRL B).

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    Step 17: Choose the paint tool and start painting the mask.

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    Step 18: Be sure that the subject is white so that anything that is not the subject would be black.

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    Step 19: Be prepared to change your brushes.

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    Step 20: Save the mask as an XCF file so that you will have the mask if you need it again.

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    Step 21: Do a Gaussian Blur (Filters >> Blur >> Gaussian Blur)) of about five pixels.

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    Step 22: Then invert the mask (Colors >> Invert).

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    Step 23: Select the original image in the drop down box.

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    Step 24: Double click on the top layer.

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    Step 25: In the original image

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    Step 26: right click and select Filters >> Blur >> Gaussian Blur.

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    Step 27: Go back to the Layers dialog and right-click on the "Blurred" layer; select "Add Layer Mask".

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    Step 28: In the Add Mask Options dialog make sure White (Full Opacity) is selected.

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    Step 29: Go to the mask image window and Select All and Copy (Ctrl+A then Ctrl+C).

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    Step 30: In the Layers dialog

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    Step 31: click on the anchor button to anchor the pasted image.

Detailed Guide

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