pnm A Portable Any Map parser http://netpbm.sourceforge.net/doc/pnm.html
psnr Peak signal-to-noise ratio, often abbreviated PSNR, is an engineering term for the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation. Because many signals have a very wid
ssim The structural similarity (SSIM) index is a method for measuring the similarity between two images. The SSIM index is a full reference metric; in other words, the measuring of image quality based on an initial uncompressed or distortion-free image as reference. SSIM is designed to improve on traditional methods like peak signal-to-noise ratio (PSNR) and mean squared error (MSE), which have proven to be inconsistent with human eye perception.
torque Control servos via a SSC or Torobot servo controller
variance In probability theory and statistics, variance measures how far a set of numbers is spread out. http://en.wikipedia.org/wiki/Variance