# ken jun

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since Apr 23, 2010
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## Recent posts by ken jun

Matthew Brown wrote:

Campbell Ritchie wrote:It seems weird that you should try putting something in an image which refers to water turning in a pipe. Which seems to be what I found when I looked for it.

It's not that specific. Curl is a general differential operator on any vector field. I just find thinking about fluid flow to be one of the easiest ways to understand what it means, because there there's a nice physical interpretation.

It also crops up in Maxwell's equations, describing the relationship between electricity and magnetism:

(E is electric field, B is magnetic field, and the "Delta x" part is the usual notation for curl).

Thank you very much. But I am still confused about how to describe it on the image field in a easily understand way ╮(╯_╰)╭
8 years ago

Matthew Brown wrote:I don't know anything about image processing, but in general the curl of a vector field is a measure of the local rotation of the field.

For example, I used it a lot in fluid mechanics. If you have a function giving the velocity of the fluid at any point, then the curl of that gives you the "vorticity" - the amount the fluid is swirling at that point. A whirlwind or tornado is an example of a high concentration of vorticity.

I'm not quite sure what that would correspond to in an image, but it would be something to do with rotation.

I check the meaning of "curl" in math and physics , but I read more I feel more confused. ╮(╯_╰)╭
thank you Matthew
8 years ago

Campbell Ritchie wrote:The only CURL I could find on Wikipedia was this. I don’t know how many mathematicians we have who are regular readers here, because they might be the only people able to help. If you post the same question elsewhere, be sure to tell people on both website about the cross-post.

thanks a lot ,if I post it somewhere else I will tell about the cross-post
8 years ago

Tim Moores wrote:I have done a fair amount of image processing work, and have no idea what you mean by "curl of an image"; where did you see that? In the computing domain, "curl" is a command line tool to access a particular URL.

I am sorry I do not express it clearly. the curl from the wiki http://en.wikipedia.org/wiki/Curl_(mathematics)

here is the code I use to count the "curl" in MATLAB

%count the gradient of an image
[rows cols dim]=size(I);

%sobel operator used to calculate gradient image
Grd=[ -1 -2 -1;
0 0 0;
1 2 1];

Emean=zeros(rows,cols);
for i=1:dim
Ev(:,:,i)=conv2(x(:,:,i),Grd,'same');
Eh(:,:,i)=conv2(x(:,:,i),Grd.','same');
E(:,:,i)=abs(Eh(:,:,i))+abs(Ev(:,:,i));

% E(:,:,i)=conv2(X(:,:,i),Grd1,'same');
end

%count the "curl"

Ecurl = zeros(rows, cols);%creat a 0 rows * cols matrix

for i = 1:dim

Ecurl(:,:,i) = conv2(Iy(:,:,i), Grd.', 'same') - conv2(Ix(:,:,i), Grd, 'same');

end

theCurl = 1/dim*sum(Ecurl,3);

8 years ago
Can anyone tell me the meaning of the curl of an image in an approachable way? Recently, I am learning image processing and don't know the concept of that. I count the curl of an image using MATLAB , it tells me that the answer is 0 except for the border of the image.
8 years ago

I really want to know whether there is a jar can get what the cmd with inputing "ipconfig" get .......I really don't want to use the method that run a thread that open the cmd and then input then get the output......

If the answer is no, that I want to write one... Will I use the API of windows? I hope you can give me some hits..thanks

jun
9 years ago

Madhan Sundararajan Devaki wrote:One more thing you need to remember, is that MS-ACCESS has its own extensions in addition to the standard ANSI SQL, hence, some DML statements may not work. For example, alter database, etc... Please check MicroSoft site for additional official information on this.

thanks for reminding me
9 years ago

Madhan Sundararajan Devaki wrote:MS-ACCESS is a product from MicroSoft.

All MicroSoft Databases can be accessed by creating a DSN

To access the MS-ACCESS database, please create a System DSN and use JDBC-ODBC method to use it in Java.

Thank you I will search what is DSN and try it later ....just finish my supper..need to rest for a moment
9 years ago
I have installed Microsoft Office 2003 and it has Access . I want to make a program with java to alter the database(Access) . How could I do it? I have search the Internet that need the drivers which connect the java to the database but I can find no drivers about Access, I can merely find like MySql Oracle and so on....
Maybe someone can provide me a very simple code to alter the database, I will appreciate you if provide me a simple Access database file..haha ...

by the way, I know that if java need to connect to MySql that it need an URL which refer to the database server, is Access do the same thing? But it doesn't seems the Access 2003 like a server program.. So could anyone tell me whether alter the Access database just need to include a particular Access file ,what I means is that the Access database just build one(or some) particular file(s), the the JAVA just need to alter it without linking to an URL?

I am not confident with my expression so if you don't understand what I want to ask , I hope you can finger out that.

thank you
jun
9 years ago

Campbell Ritchie wrote:Don't know myself, sorry.

haha no problem anyway thanks a lot
9 years ago

Campbell Ritchie wrote:System#getProperty(String). If you can't get anything useful with "encoding" try System.getProperties and iterate through the Enumeration it returns.
You should be able to select the database's properties in MySQL but I can't remember how.

Thank you Campbell

I know I can select the character encoding of the database but if I want to distribute a program for others to run, I have no idea what the user's properties. So could you tell me some method to solve the problem that how to know the character encoding which the database is using...
9 years ago
If I want to write a java to connect to the MySql ,needing to insert some data to it and then I need to convert the system's character into the database's character,but I don't know which character encoding the database is using. So how can I get the character encoding the system is using as well as the MySql.

Thanks
jun
9 years ago
I am also using win7 64bit, cause it has 8GB RAM
9 years ago
I am merely a beginner maybe

9 years ago

Pat Farrell wrote:Be careful, getting the information is restricted by some popular operating systems, including Android and OS-X. And also many Linux distributions. Once upon a time, the official command to find this was "netstat -r" but these days it varies. Sometimes "route" will give it, but nothing is guaranteed.

Obviously your use of "cmd" in the command is Windows specific.

thanks I just think about windows maybe I will try Linux later
9 years ago