Color class with support for named colors and HSV values

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Introduction

Neither ATL nor MFC have a class that encapsulates color. In the Win32 API, color can be represented as either a COLORREF value or as an OLE_COLOR value. Translation between the two is not handled automatically. The system also has its own palette which can only be translated through the use of the GetSysColor function. The .NET library defines a color class that also has named colors. And lastly, often, when working with colors, programmers need access to the HSV (hue, saturation, and brightness) properties. The CColor class is my attempt to address all of these needs.

• Class Members
• History
• Example Code

Class Members

Constructors

CColor(ULONG clrRef = -1L)

Initializes color to clrRef value. This value can be either a COLORREF value (provided by the RGB macro) or an OLE_COLOR value. If no value is provided, color is initialized as Empty (-1L).

CColor(LPTSTR szString)

Initializes color to parsed value of szString. The string format must either be a comma separated list of the decimal RGB values (e.g. "255,128,0") or the web color string format (e.g. "#ff8000").

CColor(BYTE R, BYTE G, BYTE B)

Initializes color to the RGB values provided by R, G, and B.

CColor(int nSysColorIndex)

Initializes color to the system color value of nSysColorIndex. The list of acceptable values can be found in the documentation for the GetSysColor API function.

CColor(CColor::KnownColor knownColor)

Initializes color to the value of the enumerated type value of knownColor. This constructor is only available if __KNOWN_COLORS__ is defined for the project.

Properties

R

Gets/sets the R (red) value of the color.

G

Gets/sets the G (green) value of the color.

B

Gets/sets the B (blue) value of the color.

Name

Gets the name of the color if it is a known color. Returns NULL if color is unknown. This property is only available if __KNOWN_COLORS__ is defined for the project.

Hue

Gets the hue of the color. This property is only available if __HSV_COLORS__ is defined for the project.

Saturation

Gets the saturation of the color. This property is only available if __HSV_COLORS__ is defined for the project.

Brightness

Gets the brightness (or value) of the color. This property is only available if __HSV_COLORS__ is defined for the project.

Operators

operator COLORREF() const

Returns the current COLORREF value of the color. If the color is a system color, it is translated to the actual RGB value.

CColor& operator = (ULONG clrRef)

Sets color to clrRef value. This value can be either a COLORREF value (provided by the RGB macro) or an OLE_COLOR value.

CColor& operator = (LPTSTR szString)

Sets color to parsed value of szString. The string format must either be a comma separated list of the decimal RGB values (e.g. "255,128,0") or the web color string format (e.g. "#ff8000").

CColor& operator = (int nSysColorIndex)

Sets color to the system color value of nSysColorIndex. The list of acceptable values can be found in the documentation for the GetSysColor API function.

CColor& operator = (CColor::KnownColor knownColor)

Sets color to the value of the enumerated type value of knownColor. This operator is only available if __KNOWN_COLORS__ is defined for the project.

bool operator < (const CColor& clr) const

Returns true only if current color has a lower HSV value than clr. This operator is only available if __HSV_COLORS__ is defined for the project.

bool operator == (ULONG clrRef) const

Returns true only if the translated value of clrRef is equal to the translated value of the current color.

bool operator == (LPTSTR szString) const

Returns true only if the parsed value of szString is equal to the translated value of the current color.

bool operator == (CColor::KnownColor knownColor) const

Returns true only if the current color is equal to knownColor.

Methods

void GetHSV(double& h, double& s, double& v) const

Gets the hue (h), saturation (s), and brightness (v) of the current color. This method is only available if __HSV_COLORS__ is defined for the project.

LPTSTR GetRGBString(LPTSTR szColor, CColor::StringFormat fmt = CColor::CSV) const

Builds a string pointed to by szColor and returns its value based on the specified format (fmt). Supported formats are:

• CSV - Comma separated values of the RGB values (e.g. "128,128,128")
• Web - Common web color format (#rrggbb) (e.g. "#808080")
• HexPairs - Zero padded hex values of RGB colors (RRGGBB) (e.g. "808080")

bool IsEmpty() const

Returns true only if no color has been assigned.

bool IsSystemColor() const

Returns true only if color is defined as a system color.

bool IsKnownColor() const

Returns true only if color is one of the enumerable colors defined in the KnownColor enumerated type. This method is only available if __NAMED_COLORS__ is defined for the project.

History

23 Oct 2001 - Original submission.

Example Code

//

// Example of using the CColor class

//


// Set initial values using either constructors or assignment operators

CColor clr1(CColor::Control), clr2(RGB(0,0,255)), clr3, clr4, clr5;
clr3 = "255,15,1";
clr4 = "#ff0f01";

LPCTSTR szName;
bool b;

szName = clr1.Name;          // This will return "Control"

b = clr1.IsSystemColor();    // This will return true


szName = clr3.Name;          // This will return NULL

b = clr3.IsSystemColor();    // This will return false


if (clr3 == clr4)            // This will evaluate to true

  b = clr5.IsEmpty();        // This will return true


// Set R, G, and B values

clr5.R = 128;
clr5.G = 128;
clr5.B = 128;

if (clr5 < clr1)             // This will evaluate to true since clr1 is darker than clr5

  if (clr5.IsKnownColor())   // Evaluates to true since RGB(128,128,128) is known as Gray

    if (clr5 == CColor::Gray) {
      // Get the R, G, and B values for clr1

      BYTE r,g,b;
      r = clr1.R;
      g = clr1.G;
      b = clr1.B;
    }

// Get the HSV values of clr3

double h,s,v;
h = clr3.Hue;
s = clr3.Saturation;
v = clr3.Brightness;