How can I apply high and low-pass filters to .jpeg images?

Hello,

I am attempting to apply high and low-pass filters to a series of jpeg images (yielding blurred and line-drawing versions of the source image). Ideally, I would be able to specify the sensitivity threshold in terms of cycles per degree (the edge function in matlab, for example, has a "threshold" parameter between 0 and 1 but I'm not sure how this maps onto c/d).

What is the correct syntax to achieve these filtered images?

Thanks,

Venkat

[Venkat]

Is it possible (using fspecial and imfilter) to adjust the sensitivity threshold of the filter (i.e., how many edges are detected / neglected by the high-pass filter or how "blurry" the low-pass filtered version appears)?

Thanks!

Venkat

[Image Analyst]

Yes, the window width and the threshold control that.

Answer 1

[Image Analyst]

Have you tried imfilter?

kernel = [-1 -1 -1; -1 8 -1; -1 -1 -1]; % Lapacian high pass.
filteredImage = imfilter(grayImage, kernel);

[irvin rynning]

But that gives negative values for the image in color How can I correct this?

[Image Analyst]

What's wrong with negative numbers? You can still use an image that has positive and negative values.