help with image filtering

hi everyone, i'm tring to use a grayscale image as a message and modulate it with a carrier. then i receive it, demodulate it and filter it to remove the carrier to see the original image. i used a butterworth low pass and fspecial('motion'); filter and then "imfilter" to filter the image. but the image i get after filtering with these is not sharp as original. also i'm using a grayscale image,after filtering the white in original is turning black and vice versa.

can someone suggest me a better filter or fix to this problem?

thanks....

[Walter Roberson]

More context for this question: http://www.mathworks.com/matlabcentral/answers/28365-help-with-reading-a-video

[rajashekar]

that is different...it was video....

[Image Analyst]

OK, then it would be nice if you had supplied more information for this question, if it's a stand alone, unrelated issue. I'm not even sure what the "fix" would be. Would it be to have the white pixels not be black, or not be blurry? Is the modulation part working, or is not even that part working?

[Walter Roberson]

Is this current question just the static picture equivalent of the previous question? If so then the main difference appears to be just that you are apparently not using an analog step in this question (which does save you a lot of effort of trying to do useful modulation / demodulation on a NTSC signal.)

Answer 1

[Image Analyst]

I don't see how your series of filters does anything like your algorithm. I don't see modulation with any carrier, and your filtering just low pass filters the image so of course it's blurry.

[rajashekar]

i took the matrix form of the image then used matrix form of a carrier and modulated both with modulation equation by matrix multiplication. then demodulated it to remove the carrier. then filter it to receive the original image....

[Image Analyst]

Posting some code would really help because that doesn't address my comment. I don't see how fspecial(), butterworth(), or imfilter() do any of that.

[rajashekar]

ideas?

[Image Analyst]

About...? About why you didn't post code? Not really. By the way, I'm not really expert about modem (modulation/demodulation) functionality, so I probably won't be able to help you on that part.