On 10/22/2013 9:30 PM, Andreas Mueller wrote:
I would also suggest the book "computer vision" by Richard Szeliski.

For you classification problem it really depends on what you want as output and what the statistics of the data are. If I understand you correctly, you want a prediction for each label. If your images are somewhat natural, the labels are usually smooth in the sense that neighboring regions are often labelled the same way. Then it might be helpful to use an oversegmentation of the image into superpixels (for example using slic from scikit-image)
and then classify on a superpixel basis.
Each superpixel could be described by descriptors as mentioned by Joseph.
I have been planing to write a tutorial on that for a long time :-/

What are the classes? Are they semantic?

A completely different approach would be to use image-based random forests, such as implemented here:
https://github.com/deeplearningais/curfil

Hth,
Andy

Thanks Andy.

I've been dancing around the classification task trying not to give more information than I thought was useful.

The task is to classify each pixel in "matched sets" of Solar images in "near real-time". The classification labels are Solar features like (Corona, Flare, Filament, Prominence, Sunspot, etc.). A "matched set" consists of 6 temporally-related images each captured using one of 6 unique filters. This stack of 6 images (called a multi-channel image) is what is to be analyzed and classified. Since each multi-channel pixel has a depth of 6, its signature is "almost" unique with regard to Solar feature; but there is some overlap.

We presently have a custom-rolled (pixel-by-pixel) Bayesian classifier doing the task with live Solar data, but we are not completely satisfied with its performance and it is difficult/tedious to train.

I am starting to look for alternative approaches, but I am really a complete novice at this. This is my first foray into ML; nevertheless, it is very interesting to me!

-- jv


On 10/22/2013 02:35 PM, jim vickroy wrote:
On 10/22/2013 3:32 PM, Joseph Jacobs wrote:
The best book I have come across for image processing/vision + machine learning is one by Simon Prince. You can download the book from his website (http://computervisionmodels.com/). Chapter 13 gives a good intro to feature extraction.

OK, great -- just what I need! --jv

Joe

On 22 Oct 2013, at 22:27, jim vickroy wrote:

On 10/22/2013 2:47 PM, Joseph Jacobs wrote:
Hey Jim,

From my (non-expert) perspective, performing classification pixel-wise would not be ideal (please correct me if I am wrong). I think the better way would be to perform some sort of feature extraction on the image (eg. SIFT, SURF, HOG, LBP and many, many more...checkout scikit-image or google it) and to do classification using that. Which feature extraction method would be ideal for you and how you apply it would depend on the application.

Thanks for the suggestion; I'll look into that! I'm a novice, but I agree pixel-by-pixel classification would not seem to scale well. --jv


Not sure how helpful that was.

Joe

On 22 Oct 2013, at 21:10, jim vickroy wrote:

Hi,

Apologies if this is an inappropriate question for this forum.

I have a collection of (1024x1024) mono-chromatic images in which each pixel is to be labeled as 1 of several categories (e.g., 10). Furthermore, each mono-chromatic image was captured through several filters (e.g., 5).

My understanding of the sci-kit documentation is that I would train a classifier on a pixel-by-pixel basis and then apply it, to new images, on a pixel-by-pixel basis. Is that correct?

Thanks for your time.

-- jv
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