You're right - we should perform FFT for the kernel (as it shown above), but I was unable to get the code above running with FFT on the gaussian distribution. When image in frequency domain multiplied with bell-shaped function, then high frequencies gets truncated and image smoothed. It was just trick.
thnx alot for replying and helping me. i have some problems. actually i am doing my final year project. i m working on a theory named MULTISCALE RETINEX THEORY to enhance a coloured image. in that theory i have to convolv grayscale image with gaussian function. i know i can use gaussian filter that exists in l.v. but my problem is that i have to give three different values of sigma and calculate three gaussian function and then convolve the image with these func separately. so i dont know how to use gaussian filter for these three scales. those are.. 5,80 and 255. i showed u the vi with first scale. as Klemen told that image get smooth through gaussian and blurred through avrage filter. but the result of my that code in matlab is a blurred image. plz tell me
hsize refers to the size of the filter. Specifically, a filter that is Nxx Ny pixels uses a pixel region Nx x Ny in size centered around eachpixel when computing the response of the filter. The response is just how the pixels in that region are combined together. In the case of agaussian filter, the intensity at each pixel around the central one isweighted according to a gaussian function prior to performing a box average over the region.sigma refers to the standard deviation of the gaussian (see documentationfor fspecial) with units in pixels. As you increase sigma (keeping thesize of the filter the same) eventually you approach a simple box average with uniform weightingover the filter area around the central pixel, so you stop seeing an effect from increasing sigma.
The similarity between results obtained with gaussian blur (with large value of sigma) and a boxaverage are shown in the left and middle images below. The right image showsthe results of eroding the image, which is probably what you want.
h = fspecial('gaussian', hsize, sigma) returns a rotationally symmetric Gaussian lowpass filter of size hsize with standard deviation sigma (positive). hsize can be a vector specifying the number of rows and columns in h, or it can be a scalar, in which case h is a square matrix. The default value for hsize is [3 3]; the default value for sigma is 0.5. Not recommended. Use imgaussfilt or imgaussfilt3 instead.
where they say that fspecial - gaussian is not recommended.In deciding the standard deviation (sigma), you need still decide hsize which affects the blurring. In imgaussfilt, you decide the standard deviation and the system considers you the rest. I can get much more better tolerance levels with imgaussfilt and imgaussfilt3 in my systems in Matlab 2016a, example output here in the body
To make for a more convincing blur effect, isolate the foreground by moving it to a separate layer. Then, on the original layer, inpaint the foreground part so it gets replaced by textures and/or objects from the background. It doesn't need to look realistic because you're going to blur it anyway. Finally, apply your gaussian blur filter only to the background layer. That way, you'll avoid blending pixel information from the foreground beyond its original contour.
Let's try and rule out a few areas this could be attributed to. What version of Illustrator were these created in. Older files had a legacy gaussian blur that used to make Illustrator very slow, until you updated them manually.
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