C# Hex Code Shadow Gradient Generator

Question

I've had a look at here but I don't quite understand whats going on there. I'm quite new to c# and I'm trying to make a HEX code gradient generator. I am given two strings of hex codes with a bunch of step down/ups.

for example:

black: 000000 to grey: 666666
with a step of 10.

This would generate 10 different HEX codes that would build me a gradient from these two points. I was wondering how I'd go about this, or if someone could give me an algorithm for how to do this.

Thanks!

AVIDeveloper · Accepted Answer · 2012-02-23T09:20:47.470

Simple gradients perform a linear division of a range into equal sections.

For example, if we look just at the red component and we'd like to go from 0 to 250 (decimal) in 5 steps, then each section will be ((250 - 0) / (5 - 1)) = 62.5.
The values will then be: 0, 62.5, 125, 187.5 and 250.

All you have to do now is to repeat this linear division for each component.

About the alpha channel

Note that the Color data structure contains an alpha-channel value, which is not reflected in the case of your 0x666666. If you consider your value of template 0xRRGGBB and you assume that the alpha channel will be 0xFF (i.e. totally opaque), then all is well.

But if you'd like to include the alpha channel in your gradient (as seen in all examples here), then for the template 0xAARRGGBB, in your case the alpha channel will be 0, which means that the color will be totally transparent (invisible).

Contructing Color from uint

One annoying thing about Color.FromArgb() is that it accepts an int value instead of uint. Thus, feeding it with 0xFF666666 for example will throw and exception.

To overcome this, we need to dirty our hands with some bit shifting:

private static Color GetColorFromArgb( uint colorValue )
{
    Color color = Color.FromArgb(
                        (int)((colorValue & 0xFF000000) >> 24),
                        (int)((colorValue & 0x00FF0000) >> 16),
                        (int)((colorValue & 0x0000FF00) >> 8),
                        (int)((colorValue & 0x000000FF))
                    );

    return color;
}

EDIT: GetColorFromArgb Explained

To answer the question "how would you convert a hex code into RGB?", then GetColorFromArgb already converts a hex number to R,G,B, but also adds the alpha-channel information.

The input for GetColorFromArgb is a 32-bit unsigned integer. If we look at its hex representation, then its template is: 0xAARRBBGG.

GetColorFromArgb extracts the components one after the other by using bit-masks and bit-shifts, and then calling Color.FromArgb(int a, int r, int g, int b).

Here's a more elaborated version of GetColorFromArgb:

private static Color GetColorFromArgb(uint colorValue)
{
    int a = (int)((colorValue & 0xFF000000) >> 24);
    int r = (int)((colorValue & 0x00FF0000) >> 16);
    int g = (int)((colorValue & 0x0000FF00) >> 8);
    int b = (int)(colorValue & 0x000000FF);

    Color color = Color.FromArgb(a, r, g, b);

    return color;
}

If the question was how to disregard the alpha-channel, then you can create a GetColorFromRGB() method that doesn't extract the alpha information and instead passes a fixed value:

private static Color GetColorFromRGB(int colorValue)
{
    int a = 0xFF; // Fully opaque
    int r = (int)((colorValue & 0x00FF0000) >> 16);
    int g = (int)((colorValue & 0x0000FF00) >> 8);
    int b = (int)(colorValue & 0x000000FF);

    Color color = Color.FromArgb(a, r, g, b);

    return color;
}

Note that since you use 0xRRGGBB values, you can use an int instead of a uint input.

score 0 · Answer 2 · answered Feb 23 '12 at 01:03

A very simple method would be to calculate the intermediate Red, Green, and Blue component values... something like:

Dim tOriginHexColor As String = "000000"
Dim tTargetHexColor As String = "666666"
Dim tSteps As Byte = 10

Dim tOriginColor as Color = ColorTranslator.FromHtml(tOriginHexColor)
Dim tTargetColor As Color = ColorTranslator.FromHtml(tTargetHexColor)

Dim tRedStep As Byte = tTargetColor.R - tOriginColor.R
Dim tBlueStep As Byte = tTargetColor.R - tOriginColor.B
Dim tGreenStep As Byte = tTargetColor.R - tOriginColor.G

For tIndex As Int16 = 0 To tSteps - 1
  Debug.Print(ColorTranslator.ToHtml(Color.FromArgb(tOriginColor.R + tRedStep, tOriginColor.G + tGreenStep, tOriginColor.B + tBlueStep)))
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C# Hex Code Shadow Gradient Generator

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