从绿色到红色取决于值 [英] From green to red depending on the value

问题描述

我需要一个函数在 vb.net 中返回从红色(值 0)到绿色(值 100)的颜色.此外，我需要一种方法来发现字体的颜色应该是白色还是黑色，具体取决于背景颜色.

I need a function that returns a color from red (value 0) to green (value 100) in vb.net. Also I need a way to discover if the color of the font should be white or black, depending on the background color.

推荐答案

线性插值

我曾经同样需要在 winform 中的两种颜色之间进行线性插值.我会做一个例外并分享这背后的代码，因为我认为它不仅对 OP 有用，而且对其他人也有用.

I once had the same need to do linearly interpolation between two colors in a winform. I will do an exception and share the code behind this as I think it might be useful for not only the OP but others.

该函数接受 0.0 (0%) 到 1.0 范围内的 Single 值(100%).

The function accept a Single value in the range 0.0 (0%) to 1.0 (100%).

Public Shared Function Lerp(ByVal color1 As Color, ByVal color2 As Color, ByVal amount As Single) As Color
    Const bitmask As Single = 65536.0!
    Dim n As UInteger = CUInt(Math.Round(CDbl(Math.Max(Math.Min((amount * bitmask), bitmask), 0.0!))))
    Dim r As Integer = (CInt(color1.R) + (((CInt(color2.R) - CInt(color1.R)) * CInt(n)) >> 16))
    Dim g As Integer = (CInt(color1.G) + (((CInt(color2.G) - CInt(color1.G)) * CInt(n)) >> 16))
    Dim b As Integer = (CInt(color1.B) + (((CInt(color2.B) - CInt(color1.B)) * CInt(n)) >> 16))
    Dim a As Integer = (CInt(color1.A) + (((CInt(color2.A) - CInt(color1.A)) * CInt(n)) >> 16))
    Return Color.FromArgb(a, r, g, b)
End Function

所以在你的情况下，它看起来像这样:

So in your case it will look like this:

Dim value As Integer = 'A value in the range 0 - 100
Dim newColor As Color = Lerp(Color.Red, Color.Green, If((value > 0I), (Math.Min(Math.Max(CSng(value), 0.0!), 100.0!) / 100.0!), 0.0!))

亮度

关于部分白色或黑色，取决于背景"，您需要知道颜色的亮度.以下函数为黑色返回 0，为白色返回 240.因此，如果给定背景色的亮度为 <=120，则应使用白色前色.

Regarding the part "white or black, depending on the background" you need to know the luminosity of the color. The following function returns 0 for a black and 240 for a white color. So if the luminosity of a given backcolor is <= 120 one should use a white forecolor.

Public Shared Function GetLuminosity(c As Color) As Integer
    Return CInt((((Math.Max(Math.Max(CInt(c.R), CInt(c.G)), CInt(c.B)) + Math.Min(Math.Min(CInt(c.R), CInt(c.G)), CInt(c.B))) * 240) + 255) / 510I)   
End Function

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