如何在c#中更改颜色的透明度
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how to change transparency of a color in c#
提问by Shruti Kapoor
I am using SSRS reportviewer to generate a report using objects. In my program, I am asking the user to input a string of commonly known colors such as "Red", "Blue", etc. I would like to then generate three shades of this color and use this color to fill an area chart in my report. I do so my changing the opacity (alpha) of the color.
我正在使用 SSRS 报告查看器使用对象生成报告。在我的程序中，我要求用户输入一串众所周知的颜色，例如"Red", "Blue"等。然后我想生成这种颜色的三种阴影，并使用这种颜色来填充我的报告中的面积图。我愿意所以我改变了颜色的不透明度（alpha）。
This is my code that converts the string to color:
这是我将字符串转换为颜色的代码：
newitem.ChartColor = "red";
Color mycolor = Color.FromName(newitem.ChartColor);
However, now I would like to generate two more colors with same shade as red but different alpha (opacity) so that they appear lighter, something like #56FF0000
但是，现在我想再生成两种颜色，其阴影与红色相同但alpha（不透明度）不同，以便它们看起来更亮，例如 #56FF0000
I tried passing a value to the Aproperty of Color however, it is read-only.
我尝试将值传递给AColor的属性，但是它是只读的。
Any help appreciated.
任何帮助表示赞赏。
采纳答案by Ma3x
There is a method that does exactly what you need Color.FromArgb(int alpha, Color baseColor).
有一种方法可以完全满足您的需要Color.FromArgb(int alpha, Color baseColor)。
Valid alphavalues are 0 through 255. Where 255 is the most opaque color and 0 a totally transparent color.
有效alpha值为 0 到 255。其中 255 是最不透明的颜色，0 是完全透明的颜色。
Use example
使用示例
Color newColor = Color.FromArgb(newAlpha, mycolor);
回答by Aghilas Yakoub
You can set with this function
您可以使用此功能进行设置
static Color SetTransparency(int A, Color color)
{
return Color.FromArgb(A, color.R, color.G, color.B);
}
回答by Jazimov
I think what needs to be included among these answers is that the alpha value indicates how transparent the color is with 0 being the most transparent and with 255 being the most opaque. Here is a summary:
我认为这些答案中需要包括的是 alpha 值表示颜色的透明度，0 表示最透明，255 表示最不透明。这是一个总结：
A L P H A V A L U E
0 [<--- most transparent] ... ... ... [most opaque --->] 255
回答by Jim Berg
I created a handy extension method.
我创建了一个方便的扩展方法。
public static class ColorExtensions
{
...
public static Color WithA(this Color color, int newA) => Color.FromArgb(newA,color);
}
Usage:
用法：
newitem.ChartColor = "red";
Color mycolor = Color.FromName(newitem.ChartColor);
Color myColorAlt1 = myColor.WithA(0x56);
Color myColorAlt2 = myColor.WithA(0x28);
or, if you needed it right away:
或者，如果您立即需要它：
Color mycolor = Color.FromName(newitem.ChartColor).WithA(0x56);
