In the last post I discussed a certain part of the article Quantitative Biological Image Analysis by Erik Meijering and Gert van Cappellen. I continue.

Image Analysis: image in -> features out. (Possibly several images in case of video or stereo vision.) Here are a few more image processing methods that are used for analysis:

• Morphology – erosions, dilations, etc. Repeated erosions will remove small particles then you can count the rest (“granulometry”). Repeated erosions that also preserve the topology will produce “skeletonization” of objects. Robustness of topology under morphological operations interests me a lot right now.
• “Colocalization” – evaluating the degree of overlap of two biological entities differently colored.
• Fourier transform – finding periodic patterns in the image. It tells you a lot about the textures present in the image.
• Image segmentation – finding objects in the image. There are many interesting methods (watershed, active contours, topology). It would be interesting to compare them some time in the future.

These are image processing tools used for image analysis but most of image processing/enhancement tools however are just that. Sometimes it works both ways: 

• Boundaries of objects can be enhanced by means of edge detection.
• Fourier transform in combination with its inverse is used for denoising.

Computer Vision: image in -> interpretation out. Elsewhere in the article: “…image analysis… is defined as the act of measuring (biologically) meaningful object features in an image.” From this point of view,

image analysis = low level computer vision.

(BTW, that’s exactly the subject of our wiki.) Because of this overlap I prefer the term “computer vision” for this. “Analysis” is just too broad a term. Does finding the average color in the image qualify as analysis? Yes, of course. Does it tell as anything about the contents of the image? No, not a bit. I like this definition:

high level interpretation = image understanding.

There will be another post on the subject.

Update: In ImageJ’s Features page, under “Analysis” image segmentation or particle analysis isn’t even mentioned! “Analysis” means different things to different people.