Trying to dynamically name & create Hashmaps inside of a Hashmap

Programming Questions

evanlivin..

Trying to dynamically name & create Hashmaps inside of a Hashmap

in Programming Questions • 2 years ago

I'm trying to take the RGB value of pixels make them into hashmaps, inside of a hashmap. However, I cannot figure out how to dynamically create hashmaps. I tried converting the hashmap to a string and then inserting it as a key in the master hashmap, but then I have not created a hashmap inside of the master.

There must be a way to do this

HashMap hm=new HashMap();
HashMap library=new HashMap(); // Master HashMap
PImage src;
PImage dstn;
void setup() {
size(10, 10);
src = loadImage("plus.jpg");
dstn = createImage(src.width, src.height, RGB);
}
void draw() {
color temp = (0);
src.loadPixels();
src.loadPixels();
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
int loc = x + y*width;
color d = src.get(2,5);
dstn.pixels[loc] = color(d);
temp = d;
}
}
dstn.updatePixels();
image(dstn,0,0);
HashMap current_pixel = hm; // assign the current pixel a hashmap
if (library.containsKey(current_pixel)) { // if library has entry for current pixel
int val = ((Integer) library.get(current_pixel)).intValue(); //accumulator
library.put(current_pixel, new Integer(val + 1)); // add 1 to
}
else {
library.put(current_pixel,0); //adds entry & a value of 1 if entry does not exist
}
String neigh = "255,0,0"; // variable of neighbor pixel
if (current_pixel.containsKey(neigh)) { // if neighbor pixel is in hashmap -
int val = ((Integer) current_pixel.get(neigh)).intValue(); //accumulator
current_pixel.put(neigh, new Integer(val + 1));
}
else {
current_pixel.put(neigh,1); //adds entry & a value of 1 if entry does not exist
}
println(library);
println(round(red(temp)) + "," + round(green(temp)) + "," + round(blue(temp)));
}

The last print statement demonstrates how I am constructing the name from RGB values of a color.

I appreciate an help

Replies(5)

PhiLho

Re: Trying to dynamically name & create Hashmaps inside of a Hashmap

2 years ago

It might be interesting to explain the purpose of your algorithm, quite puzzling at first look...
In short, you can have a local variable as a hash map: HashMap current_pixel =new HashMap();
That's the dynamic creation you are looking for. But using a hash map as key might not be what you really want...
Instead of asking how to make work what you think what can work, perhaps you can also ask how to achieve what you want to do, possibly in a very different way...

evanlivin..

Re: Trying to dynamically name & create Hashmaps inside of a Hashmap

2 years ago

phi.iho, thanks for the response.

I am trying to read through an image beginning at one corner and keep track of relationships between the pixel on the right. That is, If the first pixel is "red" and the one on the right is blue", a hashmap is created called "red" and an entry is made with the key "blue" and a value of 1. The scanner then moves right one pixel, and creates a new hashmap called "blue" with the appropriate entries.

I'd like to only create hashmaps of the pixels present. I realize I could populate populate a hashmap with every color (in terms of RGB values) but I'd like to keep these hashmaps as small as possible.

The project is to a probability table for the relationships between pixels in an image. This will then be used to create a new image based on these probabilities. I'll also be keeping track of the relationship to the pixel below the current one being analyzed as well.

PhiLho

Re: Trying to dynamically name & create Hashmaps inside of a Hashmap

2 years ago

Uh?
I rather see a kind of algorithm to count the number of occurrences of colors.
And I fail to see why you create a hash map for one value. Although you mention " a new hashmap called "blue" with the appropriate entries" but I fail to see how you have several entries with one pixel on the right.
I fear I haven't fully understood your algorithm, nor your usage of hash maps.

Are you trying to do a Markov chain?

evanlivin..

Re: Trying to dynamically name & create Hashmaps inside of a Hashmap

2 years ago

phi.lo, I apologize for not explaining better.

I am trying to a do a markov chain, though I havent completed the algorithm to perform the calculations yet because I'm stuck on how to actually make a transition table.

My idea is to have a hashmap for each COLOR present in an image which will store the probabilities of relations to other colors. To me it seems that I should create a hashmap for each COLOR present in an image which stores pixels that appear next to it as keys and the probabilities of those neighbor pixels as the values.

If I do this I will have a large set of hash maps, perhaps 16 million. I need to have a way of calling upon these hashmaps by their name, and it seems that it would be best to have a hashmap to store these hashmaps.

Thanks again.

Jo Wood

Re: Trying to dynamically name & create Hashmaps inside of a Hashmap

2 years ago

It sounds like you just need a single hashmap. The keys of that hashmap will be a colour and the values will be a collection of integer pairs representing each colour and the number of occurrences of the key colour - value colour association. As Processing actually stores colours as integers, the following would do:

HashMap<Integer,ArrayList<int[]>> colourChain = new HashMap<Integer,ArrayList<int[]>>();

Each integer array would only ever store two numbers, the first being a colour, the second its relative frequency.

Once you have built your chain, the set of keys would be all the unique colours in your image. For each individual key, it would be associated with a list of all the colours and their relative frequencies associated with each.

However, if your Markov chain is to be useful, you need there to be sufficient repeated colours in your image to build the chain. Otherwise you just end up with thousands of different colours each associated with just one other colour. Quantising your colours first can overcome this if your image contains many thousands of different colours.

For a more elegant approach you could replace the ArrayList with a class that store the collection of colour-frequency pairs but also has a method for extracting a random selection based on the Markov probabilities.

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