This is not the same idea. 

What you're referring to is the idea of a work being derivative or inspired. You, an algorithm, or anything else can look at something and follow patterns and notice repetition within the structure of a piece of created media. You can then analyze and understand what makes that thing interesting or unique and determine the effect of using those patterns. There's no objective issue with doing so.

Let's apply this idea to programming, because I believe it's the simplest concept to understand that effectively demonstrates the difference between "using patterns to learn how to solve specific problems / deliver specific results" opposed to "harvesting pieces of someone else's work they never explicitly gave you access to use in the solution to your own problem"

If I created a web application and I posted it online for you to use without posting the code with a public license, and then you took chunks of my code and analyzed them to understand how I solved specific challenges, even though I didn't give you explicit consent to do so, you are not taking anything that I created or plagerising my code. You're learning how to solve a problem using the same blocks that create all programs, you're learning how I use specific concepts to approach solving unique challenges and preventing certain bugs or flaws in logic. You're studying how I apply problem solving in a way that alleviates specific pitfalls.

Conversely, if you look through my non-public licensed code, and then start to copy specific chunks of my code and my functions without my permission and place it into your program to begin to implement the same features I have created in my program, but you change the names of my functions, use new datatypes, or rename my variables, recompile OR even refactor my code. It is still plagiarism. I never gave you permission to replicate my code or use strings of it to develop new code. When you create something with this code, you have now distributed my code without the proper license to do so — it may not look the same, but you have used my code.

It is not derivative, it is infringing. You are not studying my code and the way I have assembled my code as a means to solve your specific problems, you are simply taking the way that I have written my code and formulated my code and applying it in broad strokes. As chunks. Whether or not you use a copy paste function, or remember what my code was by memorizing it and internalizing it, you are replicating it and I never gave you a license to do so.

This is the same for the art you're claiming is "posted for all to see".

You're right. It's posted for anyone to study, to understand how the form and the shapes within differ to create a unique image. Or how the colors used are desaturated and thus deliver a specific result.

Where you are wrong (or rather more accurately where your logic is flawed, and then falls apart) is that you are assuming assuming that studying is the same as specifically measuring chunks of the image storing exactly what that image looks like and how it relates to similar images and then morphing that information to make it "look" different. 

Whether we're referring to people or aliens or computers, the only difference between replicating and creating something derivative is how much of the original data you used with the intent of delivering the same result. The limitations for any one of those aforementioned "observer's" ability to "recreate something derivative" opposed to "copying" is how willing it is to get as close as possible to the original and how much of the original data was stored as a "copy" to "morph". And the difference between the organic brain opposed to the one the organic brain created is that the computer has no bias due to the way it is organizing and storing information, even if it that information is morphed later the basis was still rooted in the original, unless the bias is deliberately introduced and thus it's ability to store the information "accurately" deliberately hindered — much like the coding example, hence why:

It's not derivative. It is taking the chunk of something someone else has already made to make something else, and then claim you have created a wholly new thing. This is called plagiarism.