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Convolution has applications that include probability, statistics, acoustics, spectroscopy, signal processing and image processing, geophysics, engineering, physics, computer vision and differential equations. [1] The convolution can be defined for functions on Euclidean space and other groups (as algebraic structures).
In mathematics, the convolution theorem states that under suitable conditions the Fourier transform of a convolution of two functions (or signals) is the product of their Fourier transforms. More generally, convolution in one domain (e.g., time domain ) equals point-wise multiplication in the other domain (e.g., frequency domain ).
This vector length is equivalent to the dimensions of the original matrix output , making converting back to a matrix a direct transformation. Thus, the vector, ″, is converted back to matrix form, which produces the output of the two-dimensional discrete convolution. [14]
Visual comparison of convolution, cross-correlation and autocorrelation.For the operations involving function f, and assuming the height of f is 1.0, the value of the result at 5 different points is indicated by the shaded area below each point.
As seen above, the discrete Fourier transform has the fundamental property of carrying convolution into componentwise product. A natural question is whether it is the only one with this ability. It has been shown [9] [10] that any linear transform that turns convolution into pointwise product is the DFT up to a permutation of coefficients ...
The matrix operation being performed—convolution—is not traditional matrix multiplication, despite being similarly denoted by *. For example, if we have two three-by-three matrices, the first a kernel, and the second an image piece, convolution is the process of flipping both the rows and columns of the kernel and multiplying locally ...
A circulant matrix is fully specified by one vector, , which appears as the first column (or row) of . The remaining columns (and rows, resp.) of C {\displaystyle C} are each cyclic permutations of the vector c {\displaystyle c} with offset equal to the column (or row, resp.) index, if lines are indexed from 0 {\displaystyle 0} to n − 1 ...
The definition of convolution between two functions and cannot be directly applied to graph signals, because the signal translation is not defined in the context of graphs. [4] However, by replacing the complex exponential shift in classical Fourier transform with the graph Laplacian eigenvectors, convolution of two graph signals can be defined ...