User Manual - pancroma

Considerable smoothing has occurred in the image as a lot of high frequencyinformation has been removed. You can perform other useful filtering operationsusing this technique.In order to filter the low frequencies and pass the high, use a solid circle centeredon (0, 0). You can build many other useful and interesting frequency domainfilters by studying your image spectra and experimenting with masks.Gaussian Low Pass FilterLow pass filters are essentially smoothing filters. This filter convolves a usersizable Gaussian kernel with the target image. The effect is to pass lowfrequencies and filter high frequencies. In order to use the utility, open a singleband file by selecting ‘File’ | ‘Open’. Then select ‘FFT’ | ‘Image Fourier Analysis’ |‘Gaussian Low Pass Filter’. A data entry box will become visible that allows youto input the Gaussian distribution parameters standard deviation and (if you wish)distribution amplitude.If the ‘Un-Normalized Distribution’ check box is not checked (default) then theGaussian distribution will be normalized so that pixel brightnesses of theprocessed image will remain approximately the same as in the source image. Ifthe box is checked, the convolution kernel will not be normalized.290