Casting a RGB string to a Color type

Question

I am reading from a file that has a list of RGB values, i.e.

0,1,6
0,2,6
0,43,170
0,42,168
0,44,175
0,44,176
0,44,176
0,221,255
0,222,255
0,222,255

I have stored all these values into a string[] array, with this constructor:

    public Program(int rows, String fileLocation) {

        int i;
        String line;
        count = 0;
        this.rows = rows;
        this.fileLocation = fileLocation;
        stringArray = new String[rows];

        try {
            System.IO.StreamReader file = new System.IO.StreamReader(fileLocation);
            for (i = 0; i < rows; i++) {
                while ((line = file.ReadLine()) != null) {
                    stringArray[i] = line;
                    count++;
                    break;
                }
            }
        }
        catch (Exception e) {
            throw (e);
        }
    }

I wanted to convert these current Strings to Color values, as they are just RGB values in the form of Strings.

So I used this method:

    public Color[] convertToColorArray() {
        for (int i = 0; i < rows; i++) {
            colorArray[i] = System.Drawing.Color.FromArgb(stringArray[i]);
        }
        return colorArray;
    }

With that said, I am getting the following error:

Telling me I have an invalid arg. I understand that the argument is not necessarily something like this 255,255,255 which are three ints separated by commas, but my string input is in that format. What is it I should do? Should I cast it to something? Should I simply store those values into a Color[] in my constructor in the beginning?

Answer 1

look at the overloads for Color.FromArgb, they all expect int to be passed in. So no, you can't just pass in a string and expect it to work. However it is not hard to turn your string in to a set of ints.

public Color[] convertToColorArray() {
    for (int i = 0; i < rows; i++) {
        //This gives us an array of 3 strings each representing a number in text form.
        var splitString = stringArray[i].Split(','); 

        //converts the array of 3 strings in to an array of 3 ints.
        var splitInts = splitString.Select(item => int.Parse(item)).ToArray(); 

        //takes each element of the array of 3 and passes it in to the correct slot
        colorArray[i] = System.Drawing.Color.FromArgb(splitInts[0], splitInts[1], splitInts[2]); 
    }
    return colorArray;
}

This code all assumes your source file is well formed so that string.Split will always return at least 3 arrays and int.Parse will never fail at parsing the input.

Answer 2

I use an extension method of string to handle without throws using transparent as fallback:

    private static System.Drawing.Color ToColor(this string color)
    {
        var arrColorFragments = color?.Split(',').Select(sFragment => { int.TryParse(sFragment, out int fragment); return fragment; }).ToArray();

        switch (arrColorFragments?.Length)
        {
            case 3:
                return System.Drawing.Color.FromArgb(arrColorFragments[0], arrColorFragments[1], arrColorFragments[2]);
            case 4:
                return System.Drawing.Color.FromArgb(arrColorFragments[0], arrColorFragments[1], arrColorFragments[2], arrColorFragments[3]);
            default:
                return System.Drawing.Color.Transparent;
        }
    }

Note that I'm using C# 7. Maybe you'll have to tweak for C# version that you are using.

Answer 3

The function you're trying to call takes 1-4 parameters

http://msdn.microsoft.com/en-us/library/system.drawing.color.fromargb%28v=vs.110%29.aspx

Assuming you're sure you have three values in each line - this should work

string[] splitArray = stringArray[i].Split(',');

System.Drawing.FromARGB(Int32.Parse(splitArray[0]),Int32.Parse(splitArray[1]),Int32.Parse(splitArray[2]);

You can write this cleaner if you convert the Array into an array of int[] beforehand

int[] intArray = splitArray.Select(sa => Int32.Parse(sa)).ToArray();

then you can just call intArray[0] et cetera.

Answer 4

The FromArgb method expects a single ARGB Int32 value, not what you want. Try this instead:

var items = stringArray[i].Split(",").Select(k => int.Parse(k)).ToArray();
colorArray[i] = Color.FromArgb(items[0], items[1], items[2]);

Answer 5

Something like this?

var colors = File.ReadLines(fname)
    .Select(line => line.Split(','))
    .Select(p => Color.FromArgb(byte.Parse(p[0]), byte.Parse(p[1]), byte.Parse(p[2])))
    .ToList();

Answer 6

you need to take the string, split it by the comma delimiter and then finally for each one, convert it into an int and then finally, put it in the FromArgb method.

Answer 7

FromArgb has an overloaded method that accepts 3 integers as parameters, one for R one for G and one for B.

Split your stringArray[i] into 3 integer parts(should be easy, bcoz they r separated by commas) and pass them to the method.

Hope this helps!