GIMP color reductions for 2 color “portraits”

The many faces of Rocco

The image is used with the kind permission of Rocco’s owner. I have used this image before, when I posted previously on some ways to reduce colored images to B/W for possible knitting using a Mac computer, please see post on 013/03/14/ color-reduction- conversions-mac-os/. Gimp offers some alternatives to the familiar dithers and is available, free, for both PC and Mac platforms. Tutorial links on Gimp edge detection available online as of May 2019 are listed at bottom of the post.

Image_Mode_Indexed_ one bit black: immediate result, too dark

Threshold adjustments may not be made in indexed images to alter the above image, so it’s back to grey scale. Reductions to grey scale may be achieved through Image_ Mode_ Greyscale or choosing Colors_Desaturate_OK options. Desaturation offers additional choices

Image_Mode_Greyscale

Colors_Desaturate_OK

rocco desaturated, in “knittable portrait size”

using edge detection and its algorithms

Difference of Gaussians

what happens if in addition color_ invert is used with Roberts

adjusting B/W with Threshold

after a bit of “tweaking”

Image_Mode_Indexed, rendering it “knittable in 2 colors”

getting silly with filling the ground with pattern behind the floating head

From the Gimp manual: image conversion to indexed  and color map dialogue 

As for camera portrait apps: Snapdot (originally 1.99, free in 2018) will render dotted “artworks”

I had no luck reducing this to one bit recognizable 1 bit B/W in PS, but here is the GIMP version in “knittable ” size

Hyperdither 150X154  pixels

Onebitcamera, another fun tool, has not been updated for latest versions of Mac OS and associated devices

5/4/2019 Other than GIMP: after straightforward load, convert, save, with no other adjustments, images shown in approximate 150 pixel/sts in width, no significant change results with conversion to color B/W indexed
http://gazs.github.io/canvas-atkinson-dither/
https://29a.ch/2016/08/04/ditherlicious-1-bit-image-dithering
and using the same software, slightly different settings

GIMP tutorials on edge detection
http://www.learnerswings.com/2014/05/how-to-use-edge-detect-function-in-gimp.html
https://visihow.com/Detect_Edges_in_an_Image_in_the_GIMP_Application
https://docs.gimp.org/en/filters-edge.html
https://www.youtube.com/watch?v=wf6bs_vW1IU

Dithering explained 

From a 2013 post, I no longer have the program available to me: Photoshop offers a myriad of additional options for converting images between color modes see help.adobe.com   diffusion, halftone, pattern, custom

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