MATLAB - roifilt2 ambiguity in description

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  • Thread starter mikeph
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In summary: This means that for the 5x5 averaging filter, only the single pixel within the ROI will be modified and the surrounding pixels outside the ROI will not be affected. It is important to specify the ROI accurately to ensure only the desired pixels are modified. Overall, the roifilt2 function uses the correlation kernel h and the binary image BW to filter the data in I and returns an image with filtered values for pixels within the ROI and unfiltered values for pixels outside the ROI. "In summary, roifilt2 is a function that filters data in I using a correlation kernel h and a binary image BW as a mask for the region of interest, resulting in an image with filtered values for pixels within the ROI and unfiltered values for pixels
  • #1
mikeph
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J = roifilt2(h, I, BW) filters the data in I with the two-dimensional linear filter h. BW is a binary image the same size as I that defines an ROI used as a mask for filtering. roifilt2 returns an image that consists of filtered values for pixels in locations where BW contains 1's, and unfiltered values for pixels in locations where BW contains 0's. For this syntax, roifilt2 calls filter2 to implement the filter.

For reference^

So as I understand it h is a "correlation kernel" which describes any number of filters. Average, sharpening, whatever. So say mine is a 5x5 averaging filter to blur my image.

Now, when I set my region of interest in BW, I tell roifilt2 which pixels to bother with. so say I set it to a single pixel. Only that pixel is modified, but what I don't know is are the other pixels surrounding it used in this modification?

Surely if you want to specify a region of interest, anything outside this is not of interest, so it shouldn't be used in the filtering process. But I have a feeling it is. Does anyone know if it is or not?
 
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  • #2
No, the other pixels surrounding the ROI are not used in the filtering process. The ROI is used as a mask over the image and only pixels within the ROI will be modified.
 

1. What is MATLAB roifilt2?

MATLAB roifilt2 is a function in MATLAB that allows for filtering of an image within a region of interest (ROI). This function takes in an input image and a binary mask that specifies the ROI. It then applies a filter to the pixels within the ROI and outputs the filtered image.

2. How do I specify the ROI in MATLAB roifilt2?

The ROI can be specified in two ways: by providing a binary mask or by providing the coordinates of a rectangle. The binary mask is a logical array where the pixels within the ROI have a value of 1 and the pixels outside the ROI have a value of 0. The rectangle coordinates are specified as [x, y, width, height].

3. What does the ambiguity in description mean?

The ambiguity in description refers to the fact that the input arguments for MATLAB roifilt2 can be specified in two different ways, as mentioned in the previous question. This can lead to confusion for users who are not familiar with this function.

4. Can I use multiple filters with MATLAB roifilt2?

Yes, MATLAB roifilt2 allows for the use of multiple filters. The filters can be specified as a cell array, and the function will apply each filter to the ROI in sequence. This is useful for applying different types of filters to the same ROI.

5. How do I view the filtered image in MATLAB roifilt2?

The filtered image can be viewed by assigning the output of the roifilt2 function to a variable and then using the imshow function to display the image. Alternatively, users can also use the imtool function to view the filtered image with additional features such as zooming and adjusting contrast.

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