Here's a list of my patents as of November 13, 2017. Each of the patents is linked to its page on Google.

All of the patents listed here are subject to the following patent grant:

Whereas, Raph Levien (hereinafter "Inventor") has obtained patent protection for related technology (hereinafter "Patented Technology"), Inventor wishes to aid the the GNU free software project in achieving its goals, and Inventor also wishes to increase public awareness of Patented Technology, Inventor hereby grants a fully paid up, nonexclusive, royalty free license to practice the patents listed below ("the Patents") if and only if practiced in conjunction with software distributed under the terms of any version of the GNU General Public License as published by the Free Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111. Inventor reserves all other rights, including without limitation, licensing for software not distributed under the GNU General Public License.

9230350B2 Method and apparatus for interactive curve generation
6097855 Method and apparatus for image rotation
5991513 Method and apparatus for suppressing moire patterns
5917614 Method and apparatus for error diffusion screening of images with improved smoothness in highlight and shadow regions
5544258 Automatic tone correction of images using non-linear histogram processing
5524162 Method and apparatus for adaptive sharpening of images
5442461 Screen generation for halftone screening of images with reduction of irrational correction artifacts
5404137 High speed transition signalling communication system
5402726 Register mark
5388517 Method and apparatus for automatic alignment of objects and register mark for use therewith
5365602 Integrated half-tone screening and enlarging using an enlargement mapping pattern having linked, unique pattern segments
5337264 Time reversal gaussian approximation filter
5331429 Digital generation of halftone images with error diffusion and frequency matched periodic screen rulings
5315406 Screen generation for halftone screening of images using arbitrary distribution of transformed screen coordinates
5307181 Screen generation for halftone screening of images using scan line segments of oversized screen scan lines
5291310 Screen generation for halftone screening of images
5276535 Method and apparatus for halftoning of images using grayscale error diffusion
5218386 Eyeglasses with spectral color shift
5155588 Color correction and apparatus for photographic reproduction
5055942 Photographic image reproduction device using digital halftoning to screen images allowing adjustable coarseness
4523271 Software protection method and apparatus home