MATLAB: How to find the length of an object in an image

Image Processing Toolbox

Hi,

I am new to image processing and I am looking for a way to find the length in cm of an object in an image. In particular, I am dealing with images of human body segments like feet, hands etc.

Thanks

Best Answer

You can use regionprops. See a Image Segmentation Tutorial demo in my File Exchange: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862.

Also see VisionBib http://www.visionbib.com/bibliography/contents.html to find papers on body part segmentation.

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MATLAB: IMAGE ANALYSIS: Do I have to convert the grayscale AFM images into binary before doing edge detection/segmentation

"Is imbinarize(image) a necessary step to find connected objects and such?" Yes. Well, not necessarily imbinarize, but binarization from some method, like manual thresholding like

binaryImage = grayImage > someThreshold;

"Is it important to binarize grayscale images to do edge detection, segmentation of different foreground shapes, etc?" No Edge detection can be done on gray scale images. Segmentation is the process of applying various operations until you get to a point where you can threshold to produce a binary image. The binary image is the "segmented" image. If you then apply a label (ID number) to each connected blob, for example with the bwlabel() function, then that is now called a "labeled" image.

See my File Exchange for a variety of ways to segment gray scale and color images.

MATLAB: How to calculate area in a binary image

Hi Asmalina,

1) To find the area in pixel size we just need to find the number of white pixel which would be

area = bwarea(bw);%bw is your binary threshold image

The unit would be pixel

2) To find the area in real world units , you need to find out how big one pixel is in appropraite units, if you working with DICOM image refer to this answer.

Another way is we can find the percentage of white area so if you have the plate area , you can find out the actual white area then.

to find out the percentage area:

percentageWhite = nnz(bw) / numel(bw);

Best Answer

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MATLAB: IMAGE ANALYSIS: Do I have to convert the grayscale AFM images into binary before doing edge detection/segmentation

MATLAB: How to calculate area in a binary image

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