Well that question depends very much on what you mean by 'compare'.  If you simply want to compare the values at each index you first need to ensure that both arrays are the same length; then you can iterate over them and check the values at each index.  So assuming int arrays as in your example:

1. for (int i=0; i < arrayLength; i++) {
2.     if(arrayA[i] == arrayB[i]) {
3.         println("match at index: " + i);
4.     }
5. }

However the answer is potentially more complex, depending on your requirements.  What if the contents of the arrays aren't sorted and you want to check they both contain the same values regardless of index position?  In that case you might have to iterate over the second array for each value in the first array; but then if you're working with very large arrays this could be rather inefficient...

If that doesn't answer your question you might need to be a little more specific.

Thanks blindfish.

I wanted a generic function that returned a true or false. However, I may have to cycle through each and compare.

You mentioned sorting. I would sum as I scan through and if the two sums are the same then they are mathematically the same. If the there is no difference until the end, they are procedurally the same.

However, if I start at the bottom of one array and start at the beginning how can I compare the two arrays?

The comparing each value only works if the two arrays are the same size and I start at the same point.

Thanks again.

The point is there is no 'generic function' to compare two arrays as 'equality' depends very much on your intentions; which you haven't yet made clear.

So if all you're interested in is whether they both add up to the same value then it's far simpler to sum each array independently and then compare the sum; though of course that's no guarantee that the two arrays contain the same int values.  If you need to check whether the values in each array are identical at each index (i.e. the arrays are identical and in the same order) then the loop I posted would work.  And if you wanted to check whether all values from the first array were present in the second array, regardless of order, you have two options.  Either start by sorting them and then using the previous suggestion; or iterate over the second array for each value in the first.  This is achieved easily enough with a nested loop, and then comparing the lengths of the two arrays to ensure equality; assuming all elements are matched:

1. int matchedValues = 0;
   
2. for(int i=0; i < arrayA.length; i++) {
3.     for(int j=0; j < arrayB.length; j++){
4.         // we can now compare each value in arrayA to each value in arrayB
   
5.         if(arrayA[i] == arrayB[j]) {
6.             println("value:" + arrayA[i] " is present in both arrays");
7.             matchedValues++;
8.             // no point continuing once we've confirmed there's a match...
9.             break;
10.         }
11.     }
12. }
13. // check if the arrays are 'equal'
    
14. if(matchedValues == arrayA.length && arrayA.length == arrayB.length) {
15.     println("arrayB contains the same values as arrayA");
16. }

Actually you'd do better to check the lengths matched first as if they don't that's obviously going to save you from wasting time iterating over them...  Also which option you use (sorting + a single loop or nested loops) will again depend on your needs.  You may not want to change the order of the values in the arrays, in which case the nested loop is the better option.  Alternatively you could create copies of the two arrays to avoid affecting the order of the source arrays.  I must admit I'm not sure which of these options is the best in terms of performance and you should also consider alternative storage options (e.g. ArrayLists) which may be better suited for comparisons and may even have methods specifically for testing 'equality' (actually I'm guessing this is what you meant by a 'generic function' - so the answer may actually be to use an alternative storage mechanism).

Thanks blindfish, you've been a great help.

I will try what you suggested.

Basically, I am using colors to track movement,
x-red
y-green
z-blue
alpha-movement x
hue- movement y
saturation - movement z

x,y and z can only range from 0 to 255

I am trying to create a customized alogirithm for motion detection.

So far I can track individual points. Now that I am inserting animation... I want to only update the next image if there is any movement.

I don't want to start at the beginning of the array just where the last movement occured.

Thanks again.

My two cents: if you want to check whether the values are identical at each index then it is probably easiest to use Arrays.equals()

No camera will ever give you a match between two frames. Hello nature! ;)

just checking of the values are different probably wont work.
There is to much noise i guess.

but did you check out this example by golan levin ?

http://processing.org/learning/library/framedifferencing.html

This is why I have so much respect for the raw power of processing.

When we look at the ocean is it really blue or is just reflecting the sky colour due to it's composition ? Basically what I am saying is that all colours run from 0 to 255, only when you involve movements does this come into modification. I agree that the one to one comparison of pixel colour is affected by noise, (aka light in the room for one, the camera can shake)

Basically one of the huge reasons I love processing it's pixel array manipulation. You can take any 2d image or data (same thing in processing) and in real-time process it and present it in 3D or what I am trying to do.

I have an algorithm that analyzes each pixel's red, green and blue value, map these to a three dimensional grid due to movement. Once that you are done you continually refer back to the pixel array to check for velocity, lateral movement.

These efforts are presented on a 2D screen obtained from a 3D environment. Once you translate the data as 3D ... you now get a one - to - one relationship. After that movement does not even have to be determined by how bright a pixel is.. you just have to check to see if it has moved, where, plot it then apply the brightness.

Wow man o man does this great using 2D animated films like Ghost in the Shell and Ninja Scrolls.

A friend I met on the old processing.org forum and myself are creating a "Elevator Surfing" sketch. Basically it uses this algorithm to apply it to an animated film clip. The algorithm picks up movement and fills the surrounding three dimensional space with the pixels that have moved. The effect is numbing to say the least.

Processing is just used for the proof-of-concept,but we are going to use a metal container (those huge 20',40' containers for shipping goods) and converting it to a theatre of sorts where you can watch animated films using this idea.

I can't describe how it looks, you would have to see it for yourself to understand the awesomeness of Processing in a real-time 3D environment !

Processing rocks!

sounds like the khronis projector or some of the projects mentioned here  :


http://www.flong.com/texts/lists/slit_scan/

Hey,,