This program implements K. He et al. guided filter as described in:

• He, Kaiming, Jian Sun, and Xiaoou Tang. "Guided image filtering." European conference on computer vision. Springer, Berlin, Heidelberg, 2010.
• He, Kaiming, Jian Sun, and Xiaoou Tang. "Guided image filtering." IEEE transactions on pattern analysis and machine intelligence 35.6 (2012): 1397-1409.

To execute this program you need octave, a C compiler and make.

First install Octave's image package. Start Octave by typing octave in a terminal, then simply do

pkg install image

from the Octave prompt.

Then compile the mex files that make the interface between Octave and iio (included). Simply type

make -C iio

This will create the files iio/iio_read.mex and iio/iio_write.mex which are used to read and write images in Octave.

Print the program's help by calling it without arguments

./denoise_with_gf.m

this outputs:

./denoise_with_gf input guide output epsilon radius
- input  : path to input image
- guide  : path to guide image use "NULL" if no guide
- output : path to output *directory* (created if needed)
- sqrteps: square-root of epsilon: amount of smoothing, in (0,255]
- radius : patch size = (2*radius+1)^2

All common image formats can be read and written, and some less common too. In particular, floating point tiff images are handled.

A good value for sqrteps is the standard deviation of the noise; a good value for radius is 1 or 2% of the image width or height.

Each of the n channels of the input image are filtered using the n + m channels available, where m is the number of channels of the guide image (when no guide is provided m = 0). In this program the maximal value for n + m is 3.

The filtered image is saved in the given output directory with the same name as the input image.

Assuming we have a directory called in with the images image_vis.tif and image_ir.tif inside. We can denoise the vis image by running:

./denoise_with_gf.m in/image_vis.tif NULL out 52 7

or, using a guide, by running:

./denoise_with_gf.m in/image_vis.tif in/image_ir.tif out 52 7

In both cases the output image is saved as out/image_vis.tif.