Image processing is a subclass of signal processing

"... we may acquire a natural image, process it to enhance the picture, compress it for transmission, and then encode and transmit it in some fashion over a digital network. On the other end, the image is decoded, decompressed, and displayed to create another signal (the visible light of the display). But that isn’t the end of the story: the signal is then received by the eyes, processed further, and interpreted in some fashion by our brain. From acquisition to interpretation, the initial signal may be transformed, modified, and retransmitted numerous times. In this example, the signal underwent more than 10 transformations ..."

When a signal has continuous domain and range, we usually call it analog. When a signal has discrete domain and range, we call it digital.

"... The spacing of discrete values in the domain of a signal is called the sampling of that signal. This is usually described in terms of some sampling rate–how many samples are taken per unit of each dimension. Examples include “samples per second”, “frames per second”, etc.

The spacing of discrete values in the range of a signal is called the quantization of that signal. Quantization is usually thought of as the number of bits per sample of the signal. Examples include “black and white images” (1 bit per pixel), “16-bit audio”, “24-bit color images”, etc ..." - B. Morse, BYU, On Signals and Images

Update to AmpedFIVE

There a new update to AmpedFIVE that addresses the issue of the potential for the addition of colour information when performing unsharp mask or laplacian sharpening. Build 4156 adds the choice between Intensity and Color mode in Unsharp Masking and Laplacian Sharpening.

We've done this exercise in my Photoshop classes. How do you perform USM without adding colour to your image? How do you answer the answer, "Did you add anything to this image?" if you use USM in your workflow - and don't control the processes in some way so as to limit the adjustments to only the lightness/intensity information.

There's a number of ways to accomplish this task in Photoshop, as long as you know what's happening. You can work in LAB, and only sharpen the L channel. You can work on an adjustment layer and control the effect with the appropriate blending mode. In AmpedFIVE, it's now much easier - just select Intensity when performing your sharpening. How cool is that?!

Enjoy.

The nature of perception

From David Kelley's classic, The Evidence of the Senses: " ... The normal adult human is not a tabula rasa. We bring to perception an enormous fund of background knowledge, and the act of perceiving is usually guided by the conscious purposes of expanding or applying that knowledge. Consider, for example, the role of attention. At any moment, the way in which one directs his attention affects what is perceived from among all the things that could be perceived, given present stimulation. It is doubtful that an act of attention is necessary for perceiving every object. Stimuli such as sudden chills, loud explosions, or noxious odors intrude themselves upon us quite apart from any conscious choice. But attention certainly can make the difference between perceiving or not perceiving an object-the classic examples being one's awareness of his clothes or of a low hum in the background. And the degree of attention to an object has a marked effect on the character of one's perceptual awareness of it. Thus there are major differences in the scope, clarity, and specificity of awareness-that is, in how much of the object is perceived-along a continuum of attention from objects at the edge of the visual field, to pocket change fingered absentmindedly, to the road ahead while one is driving, to a pen one has found at last among the litter on the desk, to the face of another person in conversation, to the riveting sound of a scratching at one's door late at night. ..."

The history of what a person attends to affects what it is possible for him to perceive in a given situation. Attention is the major factor in perceptual learning.

As you can see now, after a few posts on David Kelley's book, that the science of perception - and the philosophy of perception - are quite different.

Enjoy.

Perceptual Judgments

From David Kelley's classic, The Evidence of the Senses: " ... The perceptual judgment is the conceptual identification of what is perceived. Transforming our perceptual awareness of the world into conceptual form, it gives us a way to retain and communicate what we perceive and to express the evidence of the senses in a way that can bring it to bear on abstract conclusions. My approach to the perceptual judgment is centered on this fact; my goal is to understand the link it creates between the perceptual and the conceptual awareness of objects ..."

A perceptual judgment is a belief about a particular object present to the senses.

He goes on: "... A perceptual judgment is justified by the way an object appears to a perceiver. Because the thing before him looks a certain way, he can identify it as a tree, as green, and so on. The appearance will not justify predicating these attributes of any object at random, however, but only of the particular item that appears, and only if it is picked out as a particular item. Thus I might "see" a camouflaged soldier in the sense that his facing surfaces are parts of my field of view, but I am not in a position to form a judgment about him. Nor would the appearance of the field justify such a judgment, unless I can isolate the soldier as a figure against the ground. If I cannot isolate him, but only the various patches of color that in fact are parts of his clothing, then I can form justified judgments only about those patches. This is one reason why it is important that what we discriminate in vision is ,the entity itself, not merely its facing surface ..."

This is great stuff. If you haven't read the book, I highly recommend it. Best of all, it's now free.

Enjoy.

The Evidence of the Senses

Wonderful news just hit my inbox. David Kelley's classic, The Evidence of the Senses, is now available on Scribd.com, the world's largest online library.

In this highly original defense of realism, David Kelley argues that perception is the discrimination of objects as entities, that the awareness of these objects is direct, and that perception is a reliable foundation for empirical knowledge. His argument relies on the basic principle of the "primacy of existence," in opposition to Cartesian representationalism and Kantian idealism.

This is a wonderful book for building up your vocabulary on perception as well as understanding the philosophy of perception from multiple points of view - given that we deal with how people perceive events, objects, sounds, etc. in our line of work.

Enjoy.

Open proprietary or corrupted video files

Amped Software just announced two new features contained in their latest update to AmpedFive.

File>DVR Change Container to Avi - " ... we discovered that we are able to change the container of a proprietary video file to avi and without any transcoding (meaning loss of quality) and then able to open it in Five with our standard video engines. It works only with some proprietary formats, I dare say in roughly 20-30% of cases, but in those situations this can really saves a lot of time and headaches ..." I was able to change a native Bosch file using this method. It's a cool addition to the program. In my tests, it was able to correctly process .264 files from Clover, Q-See, and Swann DVRs (really popular out here in SoCal) and work with them in FIVE.

File>DVR Convert to Uncompressed Avi - " ... We’ve worked hard to create a video decoding engine able to precisely seek frame by frame; which can be another problem with proprietary codec files. This can help with the amount of different and often non-standard compliant video formats where the frame rate is unstable. In these type of files, where the codec has bugs or is mildly corrupted (like many el cheapo DVR brands seem to produce) the seek may have major issues or won’t work at all. This tool works in a similar way to the previous one, but converts any supported format to a raw uncompressed avi. This means that the output video file will be decoded very easily by any software with no need for any codec, and the frame-by-frame seek will be always perfect ..."

Can I just say that it's refreshing to see a vendor working on the needs of image and video analysts in real time - not on an 18 month sales cycle. Users submit ideas and issues, like George asking about the Channel Mixer, and Amped responds.

Enjoy.

Point Spread Function

What is point spread function? What does it have to do with image restoration, clarification, or enhancement?

For the purposes of those arriving here from a Bing search looking for spread functions, PSF is not a type of gambling where the point spread is essentially a handicap towards the underdog. Thus the wager becomes "Will the favorite win by more than the point spread?" The point spread can be moved to any level to create an equal number of participants on each side of the wager. PSF is not a way to make money gambling.

Remember that image restoration refers to the removal or minimization of known degradations in an image. This includes deblurring of images degraded by the limitations of the sensor or its environment, noise filtering, and correction of geometric distortions or non-linearities due to sensors. The point spread function describes the imaging system's response to a point input. A point input, represented as a single pixel in the “ideal” image, will be reproduced as something other than a single pixel in the “real” image.

So, in essence, a PSF deals with a point that spreads. A point that spreads is essentially what happens when you think of blur (motion blur, camera shake, etc). The effect of motion blur transforms points into lines. Therefore, we have to find in the image a line that originally should had been a point and in the photo came up as a line.

I'll illustrate how to fix the problem of motion blur soon. But for now, I just wanted to introduce the idea of PSF.

Enjoy.

Careful inspection of DME output

Here's the scenario:

• I navigate through the DVR's menu and select two camera views for export, date, time, etc.
• I export the selected views to my USB stick.
• I open the USB stick on my laptop to check the contents. I've got 3 files, a player and two files of video (I hope).
• I launch the player and verify that I've got the requested video. Date/time/view checks out - I've got what I want.

Back in the lab ...

• I want to generate still images. The player has no image save functionality. It does, however, have an AVI save option.
• I export the file to AVI. No options are available (codec, uncompressed, etc.)
• I launch the resulting file in GOM.
• I notice something rather interesting - in the DVR player software, the requested/saved view is displayed. There is no option to go to multi-cam view or to view other camera feeds. It simply shows the requested exported file. But ... the AVI has all the camera views (16 in this case) for the requested time/date. Hmm...

So, I opened the file in AmpedFIVE. Sure enough, I can demux all the views, see each camera, and work with the file to generate still images.

I've tried to look into the DVR manufacturer, but this is all I have to go on. I'm sure that you've seen similarly limited About screens.

So the lesson here is that there might be more to your DME than meets the eye.

Enjoy.

Is the scientific method necessary in legal work?

Think you needn't be concerned with science and the scientific method if you're engaged in FVA, or work with DME or other electronic forensic science discipline? Think again.

Here's a section from an explanation of the Daubert decision:

Scientific knowledge = scientific method/methodology: A conclusion will qualify as scientific knowledge if the proponent can demonstrate that it is the product of sound "scientific methodology" derived from the scientific method.

Factors relevant: The Court defined "scientific methodology" as the process of formulating hypotheses and then conducting experiments to prove or falsify the hypothesis, and provided a nondispositive, nonexclusive, "flexible" set of "general observations" (i.e. not a "test") that it considered relevant for establishing the "validity" of scientific testimony:

1. Empirical testing: whether the theory or technique is falsifiable, refutable, and/or testable.
2. Whether it has been subjected to peer review and publication.
3. The known or potential error rate.
4. The existence and maintenance of standards and controls concerning its operation.
5. The degree to which the theory and technique is generally accepted by a relevant scientific community.

So here's a philosophical question: does the fact that you don't work for the US federal government, or that you don't work in a state that adopted the Daubert standard mean that you should not be bound by sound scientific methodology in your forensic science work?

Why Are Theories Important?

Not surprising, then, scientific research is based on theory -- all scientific research. Put another way, you can conduct research that is not theory-based -- but it is not science. Even the most rigorous, detailed research that fails to build on or contribute to a theoretical framework does not meet the true test of scientific discovery. It creates knowledge -- but not science. I personally have a very hard position on this. There’s lots of research, but a lot of it is not science.

So, why are theories important?

• They explain the relationships between two or more different phenomena.
• They unify observable phenomena.
• They permit us to formulate hypotheses or propositions.
• They raise research from the descriptive to the explanatory.

If you think that you are engaged in forensic science, check your assumptions, your hypothesis, and your theoretical framework. 

What's a theory?

Theory: The Layman’s Usage
The popular definition of a theory is that it is a guess, a speculation or a suggestion. “My theory is that he is German, but he could be Swiss.” This is not at all what is meant by a scientific theory

Theory: Scientific Usage
A scientific theory is a unifying and self-consistent explanation of fundamental processes or phenomena that is totally constructed of corroborated hypotheses. It is as far as you can get from a guess. It is built on reliable knowledge acquired through rigorous research.

The Centrality of Theory
Theory is central to science because theory unifies knowledge. Scientific theories explain by unifying many once-unrelated facts or corroborated hypotheses. Theories are the strongest and most powerful explanations of how the universe works. Theories can only be disproved. By definition, if we still consider it a theory, it hasn’t been disproved yet.

Source: M.E. Swisher, University of Florida IFAS

Training schedule

I'm hitting the road this fall. When the City's broke and can't pay overtime, they give time on the books. What better way to spend the time off than going out and training folks.

First on the list is HTCIA. I'll be there helping FinalData spread the good news about their superior analysis tools (I was at HTCIA last year talking about using FinalMobile to get everything off Samsung handsets). Living and working in a largely CDMA area, FinalMobile my tool of choice in assuring that I get a proper analysis - and get everything - off a mobile device. Yes, I know, I'm the video guy. But, video and images come from all sorts of places - including mobile devices like phones, iPads, iPods, and such. You'll want the best toolset to get the evidence, which is why FinalMobile is part of mine. (Yes, I know, Cellebrite UFED is easier to use ... but it doesn't always get everything off the device. FinalMobile will even work with a Cellebrite physical dump - cool.)

Next, it's off to Vegas (baby) to conduct a week-long session for Amped on AmpedFive. Although they're a bit quiet about it, you can bundle training into your software purchase in 2 day (Basic), three day (Basic - Intermediate), or 5 day (Basic - Advanced) sessions. They're really flexible about how they handle their training, either at their North American HQ in Las Vegas, in my training centre in Pasadena, Ca, or at your location. All it takes is a call or e-mail to set it up.

Then, after a brief rest, it's off to the LEVA conference in San Diego to present a session on Image Processing Fundamentals. Like I'm doing here on the blog, at the conference I'll be discussing the science behind the tools that we use every day and how it can be incorporated into your FVA testimony.

Finally, I'll be at the NaTIA Pacific Chapter conference talking about image authentication and some new tools that are coming on the market. The date/location is still TBA.

It's been a busy year, and this fall is no different. Regardless of who I'm working with, or the topic that I'm presenting, I'll always bring the viewpoint of helping us help the trier of fact correctly present, view, and interpret digital multimedia evidence. As such, I won't let blind loyalties to a single vendor's product get in the way of informing you as to what's out there and how to use it appropriately.

Enjoy.

PixInsight first look

Wow. If you want total control over every function involved in image clarification, PixInsight will blow your mind.

First of all - every clarification function that you want to do to an image is in PixInsight. You'll need to know about image processing fundamentals to know what it's called within the software, but it's in there.

So, I loaded an image - the famous SUV example - and popped open the CurvesTransformation process.

Very simply, this one panel allows me to control everything. Each of the RGB channels, the RGB/K, the LAB mode channels, hue, and saturation - without converting modes or switching to a new panel. All of that control in a single panel. Cool! In less than 30 seconds, I corrected the image.

So far ... I'm liking what I'm seeing. All this and FFT too ... !

Enjoy.

PixInsight vs. Photoshop

A reader sent me a tip about a specialty application called PixInsight, asking what I thought about it for image analysis. So, I sent them a request to review their software. Never heard of them? Here's where they place themselves on the image processing spectrum:

"PixInsight and Photoshop are two very different applications. They are in fact so different in their goals, in the way they have been conceived, and in how they are being developed, that we actually think that PixInsight and Photoshop represent, in many aspects, two opposite ways of understanding image processing. So if you are using Photoshop, or a similar application, then PixInsight cannot be a replacement: it can only be a change.

PixInsight pursues a scientific, highly technical approach to image processing. Most of our tools have been designed to solve the problems specific to astrophotography and other technical imaging fields through rigorous and flexible implementations, where the user has full control on every relevant parameter of each applied process. While we try to design and implement our tools to facilitate the user's work as much as possible, ease of use is not one of our main goals. In general, we make no concessions to simplification: there are no fast-food solutions in PixInsight. Versatility, efficiency, powerful tools, rigorous implementations and the development of astrophotography through image processing culture are the main elements of our vision and our mission as the developers of PixInsight.

Photoshop has not been conceived or designed to solve the kind of problems that arise in highly technical imaging fields, of which astrophotography is one of the most demanding ones. Photoshop is a general-purpose image edition application. It is excellent for image edition and retouching but it doesn't qualify for astrophotography because it lacks the necessary algorithms and tools; it is simply not based on the correct principles to provide the required solutions. Photoshop pursues a simplified approach to image manipulation, where the user has little or no control over the applied processes. Due to its lack of resources and to the inadequacy of its implementations, Photoshop is being applied to astrophotography through tricky procedures, including arbitrary manual manipulations and retouching practices without documentary and algorithmic basis that we consider unacceptable in astrophotography.

Hand-painted masks, arbitrary manual selections, retouching, unrigorous layering techniques and other 'magical recipes' are just the opposite of what we understand by astrophotography. Contrarily to what it may seem at first sight, these procedures tend to block your creativity: they teach you nothing about your data and don't require you to understand your images and the actual problems you have to face and solve to build them.

PixInsight provides you with a completely different platform where you can develop your astrophotography with solid foundations. With PixInsight we want to grow your image processing knowledge, as the best way to materialize your creativity and your pursuit of excellence.

The PixInsight project originates from the inside of astrophotography. It is a software platform made by astrophotographers for astrophotographers. PixInsight is not a general-purpose product made by a large multinational company with mass-market interests. It is a highly specialized platform in constant evolution, for which astrophotography is its natural ecosystem. PixInsight is available as native 32-bit and 64-bit applications on FreeBSD, Linux, Mac OS X and Windows, and a single commercial license allows you to install and run PixInsight on any machine you own, on all supported platforms, with unlimited free updates and support. The development of PixInsight is open to the community through an integrated scripting environment (PJSR, the PixInsight JavaScript Runtime) and a comprehensive, cross-platform C++ module development framework (PCL, the PixInsight Class Library). PixInsight is our personal project and we back it with hard work every day. We are close to you and easy to reach. We are different."

Here's me smiling - I love it when geeks talk smack.

Enjoy.

Thresholding

Thresholding is the special case of clipping where the output becomes binary (black/white) - a useful process for latent print analysts.

Clipping transformations

The special case of contrast stretching where a =g =0 is called clipping. This is useful for noise reduction when the input signal is known to lie in the range [a,b]. Remember, of course, that excessive noise reduction leads to a loss of detail, and its application is hence subject to a trade-off between the undesirability of the noise itself and that of the reduction of artifacts.

FVA in American Cop Magazine

This just in from American Cop Magazine: "... Video capabilities are of special concern to street cops and investigators. This is one area which can make or break your case in the first 24 hours and is one of the greatest investigative tools we have, but unless you can get it right away, it has less worth to the investigator. Don’t get me wrong; it’s still valuable to the case, as defense attorneys really hate to see their buck-toothed, mouth-breathing client’s smiling face as he shoves a cheap chrome revolver in the store clerk’s face and announces, “give me the money.” Street cops and detectives need to use that video evidence to make a quick arrest, get the cretin off the street and protect the public from the danger these people pose.

What if a street cop, investigator or crime scene investigator could run to the station or to their laptop in the car, plug a USB drive or CD into a department Windows PC based computer and evaluate video evidence to see if it’s viable for enhancement and even enhance the video right on the spot? Now, that’s what you’d call a real investigative tool. It would be instant gratification to be able to pull out a face obscured by shadows and say, “Hey, that’s little Aloysius Farnsworth MacGillacutty, that little slime-ball hangs out over on Rose and Spruce. Let’s go snatch him up and ruin his day.”

If your department has Amped Five Software available, you just might be able to do exactly that ..."

The word's getting out about forensic video analysis - even in the mainstream LE press. How cool is that?!

Video and Image Analysis Tool Kit

Evidence Technology Magazine has many of the popular FVA tools featured in their current edition. Check it out by clicking here.

eForensics mag debuts

There's a new publication on the market - eForensics Magazine. Our friend Martino from Amped Software has a featured article in the debut issue.

An Introduction to Image and Video Forensics
"Surveillance cameras, photo enabled cell phones, and fully featured digital cameras are present almost everywhere in our lives. Martino Jerian presents an introduction to image and video forensics."

Check it out.

Channel Mixer in Amped Five

This just in from AmpedSoftware: "Another new feature has just been added to Amped Five from a suggestion by our friend George Reis, Forensic Image Analyst at Imaging Forensics and author of Photoshop CS3 for Forensics Professionals. The new filter is called Channel Mixer, and it is something familiar to many long time users of commercial photo editing software ..."

To read more about it, click here.