What is alpha blending

Alpha-blending refers to allowing a background color to show through a particular color. You use the static Color.FromArgb method to create a alpha-blended color. For example, SolidBrush redBrushSolid = new SolidBrush(Color.FromArgb(255, 255, 0, 0)); SolidBrush redBrushMedium = new SolidBrush(Color.FromArgb(120, 255, 0, 0)); SolidBrush redBrushLight = new SolidBrush(Color.FromArgb(60, 255, 0, 0)); creates three red brushes. The first argument is the alpha-blending value, from 0 to 255. The last three arguments are the RGB values, denoting in this case, red. In the picture below, all three circles use the color red, but each circle has a different alpha blending setting, allowing the white background to show through.

I need to save a color as a string and be able to retrieve it. How can I do this

Here are a couple of routines that might do what you want. ColorToString takes a color and represents it as a string that then can be passed into its companion StringToColor routine that will take the string back into a color. I think it works with all types of colors. You can download a test project. public string ColorToString(Color c) { string s = c.ToString(); s = s.Split(new char[]{’[’,’]’})[1]; string[] strings = s.Split(new char[]{’=’,’,’}); if(strings.GetLength(0) > 7) { s = strings[1] + \'\',\'\' + strings[3] + \'\',\'\' + strings[5] + \'\',\'\' + strings[7]; } return s; } public Color StringToColor(string s) { return (Color)TypeDescriptor.GetConverter(typeof(Color)).ConvertFromString(s); }

How can a translate an OLE_COLOR into a GDI+ Color object

Use the ColorTranslator class. It has methods to translate to / from OLE colors, HTML colors, and Win32 colors.

How do I desaturate a specific color?

Jon Skeet provided this solution in the MS Windows Forms News Group. [C#] double greyLevel = original.R * 0.299 + original.G * 0.587 + original.B * 0.144; if (greyLevel > 255) { greyLevel = 255; } Color desaturated = new Color.FromArgb((byte)greyLevel, (byte)greyLevel, (byte)greyLevel); [VB.NET] Dim greyLevel As Double = original.R * 0.299 + original.G * 0.587 + original.B * 0.144 If greyLevel > 255 Then greyLevel = 255 End If Dim desaturated As New Color.FromArgb(CByte(greyLevel), CByte(greyLevel), CByte(greyLevel))

How do I convert a color to integer and vice-versa?

You can do it using the FromArgb and ToArgb methods as follows: // from Color to int int blueInt = Color.Blue.ToArgb( ); // from int to Color Color newColor = Color.FromArgb( blueInt );

Is there a way to force some contrast between two colors (like background color and foreground color)?

Here is a routine that will let you do this. The code below uses the routine from our previous faq how to translate a HSB color to RGB color. [C#] /// <summary> /// Adjusts the specified Fore Color’s brightness based on the specified back color and preferred contrast. /// </summary> /// <param name=\"foreColor\">The fore Color to adjust. /// <param name=\"backColor\">The back Color for reference. /// <param name=\"prefContrastLevel\">Preferred contrast level. /// <remarks> /// This method checks if the current contrast in brightness between the 2 colors is /// less than the specified contrast level. If so, it brigtens or darkens the fore color appropriately. /// </remarks> public static void AdjustForeColorBrightnessForBackColor(ref Color foreColor, Color backColor, float prefContrastLevel) { float fBrightness = foreColor.GetBrightness(); float bBrightness = backColor.GetBrightness(); float curContrast = fBrightness - bBrightness; float delta = prefContrastLevel - (float)Math.Abs(curContrast); if((float)Math.Abs(curContrast) < prefContrastLevel) { if(bBrightness < 0.5f) { fBrightness = bBrightness + prefContrastLevel; if(fBrightness > 1.0f) fBrightness = 1.0f; } else { fBrightness = bBrightness - prefContrastLevel; if(fBrightness < 0.0f) fBrightness = 0.0f; } float newr, newg, newb; ConvertHSBToRGB(foreColor.GetHue(), foreColor.GetSaturation(), fBrightness, out newr, out newg, out newb); foreColor = Color.FromArgb(foreColor.A, (int)Math.Floor(newr * 255f), (int)Math.Floor(newg * 255f), (int)Math.Floor(newb * 255f)); } } [VB.Net] ’/ <summary> ’/ Adjusts the specified Fore Color’s brightness based on the specified back color and preferred contrast. ’/ </summary> ’/ <param name=\"foreColor\">The fore Color to adjust. ’/ <param name=\"backColor\">The back Color for reference. ’/ <param name=\"prefContrastLevel\">Preferred contrast level. ’/ <remarks> ’/ This method checks if the current contrast in brightness between the 2 colors is ’/ less than the specified contrast level. If so, it brigtens or darkens the fore color appropriately. ’/ </remarks> Public Shared Sub AdjustForeColorBrightnessForBackColor(ByRef foreColor As Color, backColor As Color, prefContrastLevel As Single) Dim fBrightness As Single = foreColor.GetBrightness() Dim bBrightness As Single = backColor.GetBrightness() Dim curContrast As Single = fBrightness - bBrightness Dim delta As Single = prefContrastLevel - System.Convert.ToSingle(Math.Abs(curContrast)) If System.Convert.ToSingle(Math.Abs(curContrast)) < prefContrastLevel Then If bBrightness < 0.5F Then fBrightness = bBrightness + prefContrastLevel If fBrightness > 1F Then fBrightness = 1F End If Else fBrightness = bBrightness - prefContrastLevel If fBrightness < 0F Then fBrightness = 0F End If End If Dim newr, newg, newb As Single ConvertHSBToRGB(foreColor.GetHue(), foreColor.GetSaturation(), fBrightness, newr, newg, newb) foreColor = Color.FromArgb(foreColor.A, Fix(Math.Floor((newr * 255F))), Fix(Math.Floor((newg * 255F))), Fix(Math.Floor((newb * 255F)))) End If End Sub ’AdjustForeColorBrightnessForBackColor

How do you translate a HSB color to RGB?

Here is a routine that does this. Note that the conversion is not precise but very close. (Please do post any better algorithm in our forums). [C#] // This does not seem to yield accurate results, but very close. public static void ConvertHSBToRGB(float h, float s, float v, out float r, out float g, out float b) { if (s == 0f) { // if s = 0 then h is undefined r = v; g = v; b = v; } else { float hue = (float)h; if (h == 360.0f) { hue = 0.0f; } hue /= 60.0f; int i = (int)Math.Floor((double)hue); float f = hue - i; float p = v * (1.0f - s); float q = v * (1.0f - (s * f)); float t = v * (1.0f - (s * (1 - f))); switch(i) { case 0: r = v; g = t; b = p; break; case 1: r = q; g = v; b = p; break; case 2: r = p; g = v; b = t; break; case 3: r = p; g = q; b = v; break; case 4: r = t; g = p; b = v; break; case 5: r = v; g = p; b = q; break; default: r = 0.0f; g = 0.0f; b = 0.0f; break; /*Trace.Assert(false);*/ // hue out of range } } } [VB.Net] Public Shared Sub ConvertHSBToRGB(h As Single, s As Single, v As Single, ByRef r As Single, ByRef g As Single, ByRef b As Single) If s = 0F Then ’ if s = 0 then h is undefined r = v g = v b = v Else Dim hue As Single = System.Convert.ToSingle(h) If h = 360F Then hue = 0F End If hue /= 60F Dim i As Integer = Fix(Math.Floor(System.Convert.ToDouble(hue))) Dim f As Single = hue - i Dim p As Single = v *(1F - s) Dim q As Single = v *(1F - s * f) Dim t As Single = v *(1F - s *(1 - f)) Select Case i Case 0 r = v g = t b = p Case 1 r = q g = v b = p Case 2 r = p g = v b = t Case 3 r = p g = q b = v Case 4 r = t g = p b = v Case 5 r = v g = p b = q Case Else r = 0F g = 0F b = 0F ’Trace.Assert(false); ’ hue out of range End Select End If End Sub ’ConvertHSBToRGB

Is there a way to find out the brightness of a Color?

There is a very convenient Color.GetBrightness method that will tell you how close a Color is to black or white. This is useful when you want to use a bright or a dark color to draw based on whether the background Color is dark or bright.

Colors

Q: Is there a way to find out the brightness of a Color?

There is a very convenient Color.GetBrightness method that will tell you how close a Color is to black or white. This is useful when you want to use a bright or a dark color to draw based on whether the background Color is dark or bright.