Convert ARGB hex string to RGB

Question

My question is very simular to Convert RGBA color to RGB only I have a Hex string not byte colour values.

I am working with EPPlus and I wish to convery cell background colours to HTML colours.
The cell backgound colours come from this property ColorType.Rgb.
Note: The property says Rgb but as the doc says it is actually Argb.

During testing I have one Red cell which has the Argb hex of #FFFF0000 but as I understand it, in HTML the Alpha is not supported and the Rgb hex for red is #FF0000.

I need to first convert the Hex strings to byte values, perform the calculation from the previous answer, convert the Rgb bytes into a hex string.

Thanks

Possible duplicate of [How do I get the color from a hexadecimal color code using .NET?](https://stackoverflow.com/questions/2109756/how-do-i-get-the-color-from-a-hexadecimal-color-code-using-net) — Drag and Drop, Oct 28 '19 at 14:48

Steve · Accepted Answer · 2019-10-26T20:18:41.037

2

You can convert the Hex string to an integer value using the base 16 as

int argb = Convert.ToInt32("0xFFFF0000", 16);

and then create your color with

Color c = Color.FromArgb(argb);

finally you can get a new hex string with only RGB values with

string rgb = $"#{c.R:X2}{c.G:X2}{c.B:X2}";

edited Oct 26 '19 at 20:18

answered Oct 26 '19 at 19:40

Steve

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Might I ask, what is the `0x`prefix for? I replaced with `#` for HTML colour. – Luke T O'Brien Oct 26 '19 at 20:00
0x is the prefix for HEX numbers. But you are correct, you need the # prefix here. – Steve Oct 26 '19 at 20:18

41686d6564 stands w. Palestine · Answer 2 · 2019-10-27T20:42:27.677

1

Why not simply:

string argb = "#FFFF0000";
string rgb = argb.Remove(1, 2);

..since the format of an ARGB hex string is #AARRGGBB (source). This is the most straightforward solution (and much faster than solutions based on conversions).

To cover the case of 4 digits instead of 8, you may use something like:

int alphaDigits = (argb.Length == 9 ? 2 : 1);
string rgb = argb.Remove(1, alphaDigits);

edited Oct 27 '19 at 20:42

answered Oct 26 '19 at 20:00

41686d6564 stands w. Palestine

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The ColorTranslator wouldn't work because Argb is not an HTML color, only Rgb is, the ColorTranslator also works for HTML color names like "Red" not the hex "FF0000". The remarks for the `To` method say `This is the commonly used name of a color, such as "Red", "Blue", or "Green", and not string representation of a numeric color value, such as "FF33AA".` – Luke T O'Brien Oct 27 '19 at 12:37
@LukeTO'Brien 1) I used this as an alternative solution to using `.Remove()` _which is the most straightforward solution_ (and it works as shown above). 2) `ColorTranslator` _**will work**_ because `FromHtml()` uses `ColorConverter.ConvertFrom` [internally](https://referencesource.microsoft.com/#System.Drawing/commonui/System/Drawing/Advanced/ColorTranslator.cs,274) which supports ARGB hex values, then `.ToHtml()` just ignores the alpha value. You may test using [this code](https://pastebin.com/h0buePBL) to confirm. – 41686d6564 stands w. Palestine Oct 27 '19 at 19:33
3) I already mentioned in the answer that `.ToHtml()` will produce color names when possible (which works for HTML) and resorts to RGB hex values when it's not a known color name. So, it's up to you to decide. If you want to use color names with HTML when possible, you may use the `ColorTranslator` solution. Otherwise, if you prefer to have hex values for all colors, you can either use the `.Remove()` solution or the one provided by Steve in his answer. – 41686d6564 stands w. Palestine Oct 27 '19 at 19:33
I added the `ColorTranslator` solution as a separate answer to include more information. – 41686d6564 stands w. Palestine Oct 27 '19 at 19:52

41686d6564 stands w. Palestine · Answer 3 · 2019-10-27T20:42:58.910

Note: This solution, although produces a valid HTML color value, that value doesn't necessarily have to be an RGB hex string as explained below. It's also significantly slower than my other solution.

A third solution would be to use the ColorTranslator class, which works because:

The ColorTranslator.FromHtml() method uses ColorConverter.ConvertFrom internally (which can parse ARGB hex values).
The ColorTranslator.ToHtml then just ignores the alpha value and only uses the RGB values to generate the string¹.

Example:

Color c = ColorTranslator.FromHtml("#FFFF0000");
string rgb = ColorTranslator.ToHtml(c);

And here's some test code to show that this solution will work with all possible ARGB hex values:

try
{
    // Incrementing by 5 to save time. We can use `++` to cover all possible values
    // but it will take a long time to execute.
    for (int a = 0; a <= 255; a += 5)
        for (int r = 0; r <= 255; r += 5)
            for (int g = 0; g <= 255; g += 5)
                for (int b = 0; b <= 255; b += 5)
                    ColorTranslator.FromHtml($"#{a.ToString("X2")}{r.ToString("X2")}" +
                                             $"{g.ToString("X2")}{b.ToString("X2")}");
    Console.WriteLine("All is good!");
}
catch (FormatException ex)
{
    Console.WriteLine($"Failed. Message='{ex.Message}'");
}

¹_{However, keep in mind that ColorTranslator.ToHtml() will not necessarily return an RGB hex string. It tries to return a color name if the color has a known color name (which works for HTML), otherwise, it resorts to RGB hex values in the format of #RRGGBB.}

Convert ARGB hex string to RGB

3 Answers3

Example:

Linked