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The objective of the Image Representation lab is:

1. to examine the difference of subsampling with and without aliasing,
2. to implement convolution with basic kernels (e.g. a Gaussian kernel, a box filter, and a gradient kernel), and
3. to build Gaussian and Laplacian image pyramids.
[ADVANCED]
4. to build a steerable pyramid (requires special kernels), and
5. to modify the code such that it works with a live video, e.g. camera.

Software

• To access the necessary files for this lab, see directory /eecs/home/wildes/prism/4422/Lab3_ImageRepresentation


• To compile sampleOpenCV.c on CentOS,
  1. Link the library location in the binary
  % setenv LD_RUN_PATH /cs/local/lib64
  2. Compile the sampleOpenCV.c
  % gcc `pkg-config --cflags opencv` `pkg-config --libs opencv` sampleOpenCV.c
• To compile sampleOpenCV.c on Ubuntu,
% gcc `pkg-config opencv --cflags` sampleOpenCV.c `pkg-config opencv --libs`

Task

• Currently, when ./a.out image is executed,
  • 'ESC'-- exits the program
  • 'i' -- inverts the intensities of the current image
  • 'o' -- knocks out every other pixel in the original image
  • 'z' -- blurs the image by applying a 3x3 filter at every pixel of the image


• Complete sampleOpenCV.c, such that
  • 'h' -- displays subsampled+aliased and smoothed+subsampled image with their FFTs
  • 'k' -- computes the convolution with the current kernel and the FFT of the resulting image is shown as well.
    The following keys must be pressed every time the kernel is changed.
    • '0' -- sets the current kernel to a 2D 1-4-6-4-1 Gaussian kernel
    • '1' -- sets the current kernel to a 5x5 box filter
    • '2' -- sets the current kernel to a simple horizontal gradient kernel
    • '3' -- sets the current kernel to a simple vertical gradient kernel
    • '4' -- sets the current kernel to a 1D horizontal 1-4-6-4-1 Gaussian kernel
  • 'g' -- displays the Gaussian pyramid
  • 'l' -- displays the Laplacian pyramid
  [ADVANCED]
  • 'o' -- oriented filtering of the pyramidal image. Every key press rotates the filter orientation by 22.5 degrees and the corresponding FFTs for each level are shown as well.