C# get good color for label

问题

I have a random color for my background in my windows forms application. Now I want to display a label.

But when the random color is white and the label also then the label is not visible.

How can I get a perfect color there is visible on my background color(My backgroundcolor is a random color from System.Drawing.Color)

回答1:

There are various ways to ensure a proper contrast.

Option one : I usually stick to keeping the text Black or White, depending on the brightness of back color.

To get the brightness one could simply go for the built-in function Color.GetBrightness()

Unfortunately this is not really a good solution, as the result is not perceptually correct; to wit: Green and Yellow have the same values, which is obviously not what our eyes will perceive.

Instead this tiny function will help:

float getBrightness(Color c) 
{  return (c.R * 0.299f + c.G * 0.587f + c.B *0.114f) / 256f; }

Now we can pick either Black or White:

Label lbl = new Label();
lbl.BackColor = colors[rnd.Next(colors.Count)];
lbl.ForeColor = getBrightness(lbl.BackColor) < 0.55 ? Color.White : Color.Black;

The code uses a list of known colors:

List<Color> colors = ((KnownColor[])Enum.GetValues(typeof(KnownColor))).
                     Select(x => Color.FromKnownColor(x)).ToList();

Option two : If you want to get colors in the foreground you could pick it randomly and repeat until you get a decent contrast by comparing e.g.

while (Math.Abs(c1.GetBrightness() - c2.GetBrightness()) < 0.5f ) 
            c2 = colors[rnd.Next(colors.Count)];

Note that you must not push the epsilon value too high or else it won't find a suitable color. This happens when trying to find a color that is too far away from a medium brightness! You could add a counter and after a while pick simply black or white..

Option three : Yet another way would be to construct a color with Color.FromArgb().

You could start by inverting each channel, which will give nice color contrasts; but if the color one is of medium brightness and/or saturation you would have to correct, maybe again by picking black or white..

Note: for the above image I have enumerated all KnownColors, which already looks pretty random.

To add some order you may sort the list by color properties, e.g. by hue, then by brightness:

List<Color> allcolors = ((KnownColor[])Enum.GetValues(typeof(KnownColor)))
    .Select(x => Color.FromKnownColor(x))
    .OrderBy(x => x.GetHue()).ThenBy(x => getBrightness(x)).ToList();

来源：https://stackoverflow.com/questions/50540301/c-sharp-get-good-color-for-label

标签

windows

forms

colors

drawing