The stunning images of Pluto sent to Earth recently draw our attention to the topic of image processing and the general notion of processing signals that have more than one independent variable. Familiar concepts for one-dimensional signal processing are easily extended to two- and higher-dimensional signal processing. We've recently uploaded two new lessons introducing these extensions. The lesson Two-Dimensional Signal Processing: Discrete Space describes linear, space-invariant systems and two dimensional convolution for discrete images. A second lesson Two-Dimensional Signal Processing: Continuous Space generalizes continuous-space convolution and the Fourier transform to two dimensions. Several additional lessons on two-dimensional signal processing are also on the way, including the two-dimensional sampling theorem and the two-dimensional DFT. Once you understand the extension of one-dimensional signal processing concepts to two dimensions, it is straight forward to further extend them to three-dimensional volume imaging such as MRI. Check out these lessons and let us know what you think.