# How does the Lum value come out and you only know the percentage of brightness like # 5b9bd5 about ForegroundColor class • ### Question

• How does the Lum value come out and you only know the percentage of brightness like # 5b9bd5 about ForegroundColor class
Friday, July 14, 2017 3:35 AM

### All replies

• Hi JellenM,

```Specifies the tint value applied to the color.

If tint is supplied, then it is applied to the RGB value of the color to determine the final color applied.

The tint value is stored as a double from -1.0 .. 1.0, where -1.0 means 100% darken and 1.0 means 100% lighten. Also, 0.0 means no change.

In loading the RGB value, it is converted to HLS where HLS values are (0..HLSMAX), where HLSMAX is currently 255.

[Example:

Here are some examples of how to apply tint to color:

If (tint < 0)

Lum’ = Lum * (1.0 + tint)

For example: Lum = 200; tint = -0.5; Darken 50%

Lum‘ = 200 * (0.5) => 100

For example: Lum = 200; tint = -1.0; Darken 100% (make black)

Lum‘ = 200 * (1.0-1.0) => 0

If (tint > 0)

Lum‘ = Lum * (1.0-tint) + (HLSMAX – HLSMAX * (1.0-tint))

For example: Lum = 100; tint = 0.75; Lighten 75%

Lum‘ = 100 * (1-.75) + (HLSMAX – HLSMAX*(1-.75))

= 100 * .25 + (255 – 255 * .25)

= 25 + (255 – 63) = 25 + 192 = 217

For example: Lum = 100; tint = 1.0; Lighten 100% (make white)

Lum‘ = 100 * (1-1) + (HLSMAX – HLSMAX*(1-1))

= 100 * 0 + (255 – 255 * 0)

= 0 + (255 – 0) = 255

end example]

The possible values for this attribute are defined by the W3C XML Schema double datatype.
```

Reference:

ForegroundColor Class

Regards

Deepak

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Monday, July 17, 2017 2:07 AM