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1hedcut_blackandwhite_12x12x-0_5x0_5x81
1hedcutReducedChallenge23

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James L. Dean


Junior Member

Registered: June 2012
Location: New Orleans
users gallery
I wrote a C program that sets a pixel to black if it is significantly darker than the pixels in a window around the pixel or white if it is significantly lighter than the pixels in the window. If neither is the case, I keep trying larger windows until the window covers the whole image. If the pixel still isn't significantly darker or lighter, I set it to white. Since a pixel can be set independently of the others, multiple threads can be used. For this image I used an initial window 12 pixels on a side, increasing it by 12 pixels each time it was needed, setting a pixel to black if its z-score was less than -0.5 or white if the z-score was greater than 0.5. Using 8 Xeon 1.6 GHz processors, it took a little over 12 hours to generate the image. But, the process was completely automatic. I used IrfanView to resize the image below the maximum size allowed for this gallery.
· Date: 6/11/2012 · Views: 2179 · Filesize: 167.3kb · Dimensions: 400 x 524 ·
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Keywords: automatic hedcut
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Janet Petty

Senior Member

Registered: January 2004
Location: Mid-South
Posts: 2,164
8/11/2012 12:04pm

WOW. Technically done and impressive to view...nice job interpreting this challenge.

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E Z T D B W
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James L. Dean
Junior Member

Registered: June 2012
Location: New Orleans
10/18/2012 7:16pm

By calculating the sum of the shades of the pixels and the sum of the squares of the shades of the pixels in each sub-array of pixels containing the pixel at (0,0), I was able to reduce the calculation of the mean and standard deviation of the shades in any sub-array of pixels to eight table look ups and a little calculation. This reduced the run time from 12 hours to 4 seconds.
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James L. Dean
Junior Member

Registered: June 2012
Location: New Orleans
10/27/2012 7:01pm

http://jdean284.bravehost.com/charcoal.html contains my open source Windows Desktop application to do this conversion. Because the application is written in Qt4, it should be possible to recompile it for Linux or OS/X.
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James L. Dean
Junior Member

Registered: June 2012
Location: New Orleans
9/14/2013 12:43pm

http://jdean284.bravehost.com/HTML5Charcoal.html will let you create similar images in many of the latest Web browsers (that support HTML5).
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