A short quiz on convolution and friends

Adrian F. Clark

  1. What is the effect of convolution with a 3 x 3 mask with each coefficient set to 1/9?

  2. The correlation coefficient between two images is a quantity that lies in the range -1 to +1. What does a value of -1 represent?

  3. What is the effect of convolving an image with the mask $$\pmatrix{0 & 1 & 0\cr 1 & -4 & 1\cr 0 & 1 & 0\cr}$$

  4. What is the effect of convolving an image with the mask $$\pmatrix{0 & 1 & 0\cr 0 & 0 & 0\cr 0 & 0 & 0\cr}$$

  5. What is the effect of convolving an image with a +-shaped mask where the central pixel is -4 and its neighbours to north, south, east and west are 1?

  6. Why is simple thresholding not especially effective at locating light features in an image?

  7. How does the time taken to perform a convolution vary with the dimension of a (square) mask?

  8. What is the effect of convolving an image with a +-shaped mask?

  9. What is the effect of convolution with the following mask? $$\frac19 \pmatrix{1 & 1 & 1\cr 1 & 1 & 1\cr 1 & 1 & 1\cr}$$

  10. The Laplacean mask is useful for:

  11.