Converting Decimal RGB Values Into a 6 Digit Hexadecimal

Recent posts have looked at the Actionscript required to convert decimal numbers into hexadecimal strings. And if we don't look any deeper everything looks hunkydory for mixing any colour we like using RGB values, and then convert to a hexadecimal number you might use to define a colour in HTML.

But we still have a problem to solve.

Low Numbers v. High Numbers

HTML and Flash can both use hexadecimal values to define colours, but the hexadecimal values must be defined as a 6 digit number - 3 pairs representing the 3 colour channels Red, Green and Blue. For example:

White: Decimal Red 255 + Green 255 + Blue 255 = Hexadecimal FFFFFF

In most cases this won't present a problem, after all decimal 255 equates to hexadecimal FF. The problem comes when the decimal value drops below 16. Lets take a look:

Decimal 255 = hex FF
Decimal 16 = hex 10
Decimal 15 = hex F
Decimal 1 = hex 1
Decimal 0 = hex 0

Notice that as soon as the decimal value drops below 16 the hexadecimal value drops into single digits. Lets see what this means in practice:

Black: Decimal Red 0 + Green 0 + Blue 0 = Hexadecimal 000

This is a problem because to convey colour values to HTML or Flash consistently we need a 6 digit hexadecimal number, but what we have here is only a 3 digit number.

To solve the problem we need to remember how hex counts. As an example let's count to thirty in hex:

0 1 2 3 4 5 6 7 8 9 A B C D E F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E

In this example values 16 and above all have 2 digits in hex. We need to find a way of making the lower numbers all have 2 digits too. This is actually very easy, in fact we do this all the time, most commonly when we write the date. Take for example 1st January 2009 written numerically - 01/01/09. We can turn a single digit number into a 2 digit number, without changing its value, very easily by placing a '0' (zero) in front (this is called prepending), like so:

1 becomes 01
2 becomes 02

All we have to do then is prepend single digit hex values with a '0' (zero), like so:

00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

If we do this we can display black as a 6 digit hex number after all:

Black: Decimal Red 0 + Green 0 + Blue 0 = Hexadecimal 000000

But how do we do this in Flash with Actionscript?

Prepending Single Digit Hexadecimal Numbers With '0' Using Actionscript

I am sure there are many and varied ways to do this, but I prefer the following method. First I will give you the code, then I will explain how it works.

/* R is defined as a value between 0-255 in a text input field by the user */

_root.calc_but.onPress = function() {
var decimalred = new Number(R);
hexred = decimalred.toString(16);
if (decimalred<=15) {
hexredfinal = "0"+hexred;
} else {
hexredfinal = hexred;
}
}

Here's how it works:

1. First we take the user inputted value (a number between 0 and 255) and pass it to 'decimalred' specifically defining it as a number.

2. Then we convert the 'decimalred' number into a hexadecimal string and pass the result to 'hexred'.

3. Then we test to see if the original value inputted by the user was 15 or less. We do this because we already know that any decimal between 0 and 15 will convert to a single digit hex number.

4. If the original value inputted by the user was 15 or less, then we use Actionscript to prepend a '0' to the converted 'hexred' value like so:

hexredfinal = "0"+hexred;

Then we pass the result to 'hexredfinal'.

5. If the original value inputted by the user was not 15 or less, then we don't prepend anything, we just pass the 'hexred' value straight to 'hexredfinal' untouched.


In this way we can make sure that in the conversion from decimal to hexadecimal, all values between 0 and 255 are shown as 2 digit hex numbers. This allows us to produce the 6 digit numbers required in HTML and by Flash.

What fun.

Manipulating Colour in Flash - #3 - Successfully Converting Decimal to Hexadecimal Using the toString Method (even with user defined variables)

My last two posts looked at how you can use Actionscript to change the colour of a MovieClip, and to convert decimal colour values into hexadecimal.

Teething Trouble

But as I work towards harnessing these techniques to make a simple colour mixer in Flash I suddenly ran into difficulty converting decimal to hexadecimal when the user defines the decimal values in text input fields.

I must confess that to begin with I spent a while being stumped by this. As I Googled around for a solution there were similar questions, but no answers. Anyway, I am happy to say, there is a solution.

No doubt some of you will have a similar problem, so let me talk you through the problem I experienced and then the solution (I hope it helps).

The Problem

In my tests the toString method easily converted a decimal defined as a variable in a keyframe to a hexadecimal as follows:

/* This works */
var R = 255;

mybutton_but.onPress = function () {
hex = R.toString(16);
trace(hex); //Returns FF
}

However, when the value of R was defined by the user through a text input box it suddenly stopped working, as follows:

/* This DOESN'T work */
/* value of R is defined as 255 in a text input field by the user */

mybutton_but.onPress = function () {
hex = R.toString(16);
trace(hex); //Returns 255
}

For some reason, when the value of R was defined in the keyframe the toString method successfully converted the decimal value 255 and returned FF, but when the value of R was defined in a text input field the toString method failed to perform any conversion on the decimal value 255 and returned 255.

Preparing to Find a Solution

When I struggle with solving these niggly little problems I often find that taking some time out and doing something else gives the mind time to unwind (and also mull over the problem without having to try out every idea instantly). The brain is a fantastic problem solver, if it is given the right conditions. As a college lecturer I know that the ideal conditions come when an individual is relaxed but alert. So, if needed, take a break, unwind, get some sleep or remove distractions. I spent the morning cutting the grass and sorting out the chickens, then in the afternoon found the solution.

The Solution

As I said before, none of my Googling revealed an answer to my problem, but as I hunted around for anything I could find that might give me a hint, or prompt an idea I came across this snippet on WikiBooks.org:

var i = new Number(555);
trace(i.toString());

I must have seen several similar examples yesterday evening and got nothing from them (too tired no doubt). But having taken a break from the problem since then, and relaxed, my brain was ready to spot the significant detail that was the solution:

var i = new Number(555);

And there it was, staring out at me. Something I had not yet tried. So I modified my code as follows:

/* This DOES work */
/* value of R is defined as 255 in a text input field by the user */

mybutton_but.onPress = function () {
var decimalred = new Number(R);
hexred = decimalred.toString(16);
trace(hexred); //Returns FF
}

Why it Works

So why didn't it work before, and what's the big difference that makes it work this time?

I suspect that the reason it did not work before was because the user defined variable 'R' was already being treated by Flash as a string and so using the toString method to convert to a string did nothing, because it was already a string to start with.

Result: 255 (string) in, 255 (string) out.

The solution is really hidden within the problem (as are so many design solutions). We are converting a decimal value (representing a colour channel intensity) into its hexadecimal equivalent. We want to do this using the toString method. However, the toString method is for datatype conversion. This means converting one datatype to another datatype, in this case a non-string into a string. For this to work we need to force Flash to treat the user input 'R' as a number so that we can use toString to convert it into a string in hex format.

The script above does this by passing the user defined decimal value 'R' to a new variable 'decimalred' - with 'decimalred' specifically defined as being a new Number. This forces Flash to treat the user defined value as a number datatype thereby allowing toString to work as expected and convert the decimal number value to a hexadecimal string.

Result: 255 (number) in, FF (string) out.

And that's a wrap.

It is precisely this kind of problem that I see as being the drawback of having come to Flash and Actionscript from a graphic design, rather than a programming background. Nevertheless, I hope that by posting my solution I have helped at least one other poor designer get to grips with with one small area of Actionscript. If my Googling is anything to go by, this may well be the only explanation of this problem on the web (at time of posting of course).

Happy coding.

Manipulating Colour in Flash - #1

Following on from my previous post, I have begun to look into how I can use Actionscript to work with colour.

This experiment looks at how we can convert decimal RGB values into hexadecimal using Actionscript.

It's very simple...

The Code

/* First we set the RGB values as decimal integers (whole numbers) from 0-255, as you would see them defined in any graphics program. This example would reproduce white, but you can change the values to be anything you like between 0-255. */

var R = 255;
var G = 255;
var B = 255;

/* Then we convert the RGB decimals to their hexadecimal equivalents. The toString method is the easiest way I have found of doing it (thanks to Colin Moock). This script takes the value of each of the variables and converts the datatype from a numeric value (in this case 255) into a string using '16' as the radix argument of the method. As a result 255 becomes FF, the hexadecimal equivalent. The code below then simply stitches the converted values of the R, G and B variables together to form a 6 digit hex number for the colour. */

trace(R.toString(16)+G.toString(16)+B.toString(16)); //Returns FFFFFF

What I like about this method is its simplicity. It would form the basis of a very simple colour mixer program, since the R, G and B values could easily be set by sliders, or the user keying in decimal values for each of the channels.

Over to you... meanwhile, I play with colour some more.