On 11/07/2014 04:05 PM, Partha Bagchi wrote:
Yes, that is the same as DOG (Difference of gaussian). :)


Hmm, checking in GIMP 2.9 on a high bit depth image, I think the algorithms really are a bit different.

Checking in GIMP 2.8 on an 8-bit image, DOG gives much more useable results than "duplicate, divide, blur". I should have checked 2.8 results before mentioning "duplicate, divide, blur". It's a cool way to make a line drawing, but it doesn't seem to work very well at 8-bit precision.

For anyone using GIMP 2.9, the "duplicate, divide, blur" method gives more useable results if you first use the Levels lower left (output) Value slider to pull all the channel values well above (0,0,0). This is because the Divide blend mode gives odd results when zero is divided by zero, going to black instead of to white.

Best regards,
Elle Stone



On Fri, Nov 7, 2014 at 3:56 PM, Elle Stone
<ellest...@ninedegreesbelow.com> wrote:
On 11/07/2014 03:34 PM, Garyfx wrote:

You mean just exchanging colors?

Well, I may have not been as articulate as I could have.  I want to take
JPG
images of trailers and turn them into line schematics or outlines.  I want
just
the line drawing or frame of the trailers like the images I attached in my
original message.

And... a simple grey background is sufficient.

Thanks


This PhotoShop-specific link explains how to use divide blend mode to make a
line drawing; the technique is the same when using GIMP:

http://blog.advancedphotoshop.co.uk/tutorials/how-to-use-the-divide-and-subtract-blending-modes-in-photoshop-cs5/



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