How do i tell if an image has a shadow or not?

1 view (last 30 days)
charuleelaa vanilavarasu
charuleelaa vanilavarasu on 21 Mar 2016
Commented: Walter Roberson on 23 Mar 2016
I'm currently working on a project to detect and remove shadows from an image assuming all my input images have shadows. Input images are those that have definite shadows (i.e) easy to determine that it really is a shadow just by looking at the image. My professor wants me to first find out if an image has a true shadow or not. If it does then proceed with the shadow detection and removal. I have no idea how to do this. Any thoughts?
charuleelaa vanilavarasu
charuleelaa vanilavarasu on 21 Mar 2016
Ofcourse i did. if he did tell me how it's supposed to be done, i would'nt be asking here would i?

Sign in to comment.

Answers (2)

Walter Roberson
Walter Roberson on 21 Mar 2016
Walter Roberson
Walter Roberson on 22 Mar 2016
Chad, in the last 24 hours, there has been activity on 339 Questions, excluding any which have been closed or deleted. That's plenty to go around for anyone who wants to answer, expert or not. I assure you, if I see one beginner answering another beginner on a MATLAB question, my reaction is "Thanks, that saved me the trouble of answering myself!" When someone new comes along and starts answering questions, I might peek in to be sure they are doing a reasonable job of answering, but if they are not making mistakes, I let them be.
Saying that this forum is about MATLAB is nothing to do with "expert" or not: it is about limited resources; it is about "appropriate venue", and it is about trying to keep the resource clear so that people who are looking for MATLAB material can find it easily.
Imagine the scenario in which it becomes known that this is a place where people can post their vague questions about their homework or honours project, and that they would get responses telling them what approach to take. It would not be just the people dealing with MATLAB who would come here: it would be the people dealing with C, C++, C#, Java, Excel python, and many other programming languages as well. It would become a homework / project tutoring center for... well, just about any topic not prohibited by law (e.g., cryptography.) "I have a project in architecture, what should I do?" "I have a project in composites (e.g., cement), what should I do?" "How do I graph this sinking loan in Excel?" You have an interest in satellite photography, but maybe someone else has an interest in sociology with an intent to do statistical analysis in SPSS, so why should we allow general discussions about satellite photography but not general discussions about statistical analysis?
You are, in short, asking that this resource be allowed to become a combination Stackoverflow and ResearchGate.
Are you familiar with The Tragedy of the Commons ? "The tragedy of the commons is an economic theory of a situation within a shared-resource system where individual users acting independently and rationally according to their own self-interest behave contrary to the common good of all users by depleting that resource."
"In addition, Hardin also pointed out the problem of individuals acting in rational self-interest by claiming that if all members in a group used common resources for their own gain and with no regard for others, all resources would still eventually be depleted. Overall, Hardin argues against relying on conscience as a means of policing commons, suggesting that this favors selfish individuals – often known as free riders – over those who are more altruistic. "
The response that we have developed is that we restrict access to the resource to those matters that have to do with MATLAB (and Simulink.) If someone has a question about what is available in the Mathworks libraries, we answer. If someone has a question about how MATLAB works, we answer. If someone has a bug related to their MATLAB implementation, we answer. But if someone wants us to find an algorithm for them, or wants us to read papers and explain them, then we say "Google is that-a-way; come back when you have a MATLAB question."
The Answers facility is not self-cleaning. People spend time behind the scenes throwing away the junk; redirecting to other resources; asking people to clarify questions; reformatting questions to be readable; telling people we won't do their homework for them; searching for questions with common themes and tagging them consistently; testing and commenting on File Exchange Contributions. My personal limit is adjusting tags on about 85 Questions or Contributions in a batch, and it isn't going to be more than 25 unless there is a ready supply of chocolate (or ice cream) in the house. The gatekeeping and the janitor work is a lot of work -- but it is also necessary to keep the resource useful.

Sign in to comment.

MHN on 23 Mar 2016
Edited: MHN on 23 Mar 2016
It is like someone come here and ask you how can I do face detection with Matlab! There are 88,500 of papers (search it in google scholar), and thousands of researchers putting years of their life to answer this question and increase accuracy of their algorithms. It is exactly the same with your question! If you are a green researcher in this field, start with theory and algorithms, then try to implement the current methods. Then if you have a question about implementation in Matlab come and ask us. I believe the link that @Walter Roberson has sent is the best answer to your question.
Walter Roberson
Walter Roberson on 23 Mar 2016
We had someone the other day asking for a way to check to see that there really was a face where VJ detected it. That has close similarities to this present Question, being open-ended, the topic of a lot of research over the years, with no real answer (and what exactly is a "face" anyhow?)

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by