How to do threshold and apply median filter

Hi, i am new to Matlab. I am currently doing some image processing, which my camera has 688x520 pixel. The image that i got is a bit noisy which i need to basically set the threshold, and apply the 3x3 median filter.

for example, if i have this 10x5 pixels,

12 12 17 16 17 27 17 12 17 10

13 23 11 12 13 13 13 13 14 15

17 15 16 16 16 19 18 17 18 19

15 17 17 17 19 19 39 19 18 12

16 16 18 18 19 19 19 10 10 16

How do i basically set the threshold, for example the max value should be 20, and if there is any value more than that, the matlab should find it in the array and the 3x3 median filter should be applied. for example in the above case, it should take

12 12 17

13 23 11

17 15 16

and

19 18 17

19 39 19

19 19 10

and from this, the median should be determined, which in the first case is 11, 12, 12, 13, 15, 16, 17, 17 which gives 14 and the second case should be 18

Thanks in advance for the help!

Answer 1

[Image Analyst]

This is what's done in my attached demo. It finds the outliers (in my case values of pure 0 or pure 255) and then replaces only those pixels with the median. You can get a binary image from thresholding like

binaryImage = grayImage > 20;