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<title>Magick++ API: Working with Color</title>
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<h1 align="center">Magick::Color</h1>
<p><a href="Color.html#Color">Color</a> is the base color class in Magick++. It is a simple container class for the pixel red, green, blue, and alpha values scaled to fit ImageMagick's Quantum size. Normally users will instantiate a class derived from Color which supports the color model that fits the needs of the application. The Color class may be constructed directly from an SVG-style color string.</p>
<h4>Quantum</h4>
The base type used to represent color samples in ImageMagick is the Quantum type. Pixels are represented by a structure of Quantum values. For example, an RGB pixel contains red, green, and blue quantums, while an RGBA pixel contains red, green, blue, and opacity quantums. The maximum value that a Quantum can attain is specified by a constant value represented by the MaxRGB define, which is itself determined by the number of bits in a Quantum. The QuantumDepth build option determines the number of bits in a Quantum.
<h4>PixelPacket</h4>
PixelPacket is the internal representation of a pixel in ImageMagick. ImageMagick may be compiled to support 32, 64, or 128 bit pixels of type PixelPacket. This is controlled by the value of the QuantumDepth define. The default is 32 bit pixels (QuantumDepth=8), which provides the best performance and the least resource consumption. If additional color precision or range is desired, then ImageMagick may be compiled with QuantumDepth=16 or QuantumDepth=32. The following table shows the relationship between QuantumDepth, the type of Quantum, and the overall PixelPacket size.
<p align="center" style="margin-bottom: 0cm"><b>Effect Of QuantumDepth Values</b></p>
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<table width="361" border="1" cellpadding="2" cellspacing="3">
<col width="102" />
<col width="121" />
<col width="111" />
<tr>
<td width="102">
<p align="center"><b>QuantumDepth</b></p></td>
<td width="121">
<p align="center"><b>Quantum Typedef</b></p></td>
<td width="111">
<p align="center"><b>PixelPacket Size</b></p></td></tr>
<tr>
<td width="102">
<p align="center">8</p></td>
<td width="121">
<p align="center">unsigned char</p></td>
<td width="111">
<p align="center">32 bits</p></td></tr>
<tr>
<td width="102">
<p align="center">16</p></td>
<td width="121">
<p align="center">unsigned short</p></td>
<td width="111">
<p align="center">64 bits</p></td></tr>
<tr>
<td width="102">
<p align="center">32</p></td>
<td width="121">
<p align="center">unsigned int</p></td>
<td width="111">
<p align="center">128 bits</p></td></tr>
</table></center>
<h3><a name="Color"></a>Color Class</h3>
<p>The Color base class is not intended to be used directly. Normally a user will construct a derived class or inherit from this class. Color arguments are must be scaled to fit the Quantum size. The Color class contains a pointer to a PixelPacket, which may be allocated by the Color class, or may refer to an existing pixel in an image.</p>
<p>An alternate way to construct the class is via an SVG-compatible color specification string (e.g. Color("red") or Color ("#FF0000")). Since the class may be constructed from a string, convenient strings may be passed in place of an explicit Color object in methods which accept a reference to Color. Color may also be converted to a std::string for convenience in user interfaces, and for saving settings to a text file.</p>
<div class="viewport">
class Color
{
public:
Color ( Quantum red_,
Quantum green_,
Quantum blue_ );
Color ( Quantum red_,
Quantum green_,
Quantum blue_,
Quantum alpha_ );
Color ( const std::string &svgColor_ );
Color ( const char * svgColor_ );
Color ( void );
virtual ~Color ( void );
Color ( const Color & color_ );
// Red color (range 0 to MaxRGB)
void redQuantum ( Quantum red_ );
Quantum redQuantum ( void ) const;
// Green color (range 0 to MaxRGB)
void greenQuantum ( Quantum green_ );
Quantum greenQuantum ( void ) const;
// Blue color (range 0 to MaxRGB)
void blueQuantum ( Quantum blue_ );
Quantum blueQuantum ( void ) const;
// Alpha level (range OpaqueOpacity=0 to TransparentOpacity=MaxRGB)
void alphaQuantum ( Quantum alpha_ );
Quantum alphaQuantum ( void ) const;
// Scaled (to 1.0) version of alpha for use in sub-classes
// (range opaque=0 to transparent=1.0)
void alpha ( double alpha_ );
double alpha ( void ) const;
// Does object contain valid color?
void isValid ( bool valid_ );
bool isValid ( void ) const;
// Set color via SVG color specification string
const Color& operator= ( const std::string & svgColor_ );
const Color& operator= ( const char * svgColor_ );
// Assignment operator
Color& operator= ( const Color& color_ );
// Return SVG color specification string
/* virtual */ operator std::string() const;
// Return ImageMagick PixelPacket
operator PixelPacket() const;
// Construct color via ImageMagick PixelPacket
Color ( const PixelPacket &color_ );
// Set color via ImageMagick PixelPacket
const Color& operator= ( PixelPacket &color_ );
};
</div>
<p align="center" style="margin-bottom: 0cm"><b>Color Derived Classes</b></p>
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<col width="227*" />
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<p><a href="Color.html#ColorRGB">ColorRGB</a></p></td>
<td width="88%">
<p>Representation of RGB color with red, green, and blue specified as ratios (0 to 1)</p></td></tr>
<tr>
<td width="12%">
<p><a href="Color.html#ColorGray">ColorGray</a></p></td>
<td width="88%">
<p>Representation of <span lang="en-US">grayscale</span> sRGB color (equal parts red, green, and blue) specified as a ratio (0 to 1)</p></td></tr>
<tr>
<td width="12%">
<p><a href="Color.html#ColorMono">ColorMono</a></p></td>
<td width="88%">
<p>Representation of a black/white color (true/false)</p></td></tr>
<tr>
<td width="12%">
<p><a href="Color.html#ColorYUV">ColorYUV</a></p></td>
<td width="88%">
<p>Representation of a color in the YUV <span lang="en-US">colorspace</span></p></td></tr></table>
<h3><a name="ColorRGB"></a>ColorRGB</h3>
<p>Representation of an sRGB color. All color arguments have a valid range of 0.0 - 1.0.</p>
<pre class="code">
class ColorRGB : public Color
{
public:
ColorRGB ( double red_, double green_, double blue_ );
ColorRGB ( void );
ColorRGB ( const Color & color_ );
/* virtual */ ~ColorRGB ( void );
void red ( double red_ );
double red ( void ) const;
void green ( double green_ );
double green ( void ) const;
void blue ( double blue_ );
double blue ( void ) const;
// Assignment operator from base class
ColorRGB& operator= ( const Color& color_ );
};
</pre>
<h3><a name="ColorGray"></a>ColorGray</h3>
<p>Representation of a grayscale color (in linear colorspace). <span lang="en-US">Grayscale</span> is simply RGB with equal parts of red, green, and blue. All double arguments have a valid range of 0.0 - 1.0.</p>
<pre class="code">
class ColorGray : public Color
{
public:
ColorGray ( double shade_ );
ColorGray ( void );
ColorGray ( const Color & color_ );
/* virtual */ ~ColorGray ();
void shade ( double shade_ );
double shade ( void ) const;
// Assignment operator from base class
ColorGray& operator= ( const Color& color_ );
};
</pre>
<h3><a name="ColorMono"></a>ColorMono</h3>
<p>Representation of a black/white pixel (in RGB colorspace). Color arguments are constrained to 'false' (black pixel) and 'true' (white pixel).</p>
<pre class="code">
class ColorMono : public Color
{
public:
ColorMono ( bool mono_ );
ColorMono ( void );
ColorMono ( const Color & color_ );
/* virtual */ ~ColorMono ();
void mono ( bool mono_ );
bool mono ( void ) const;
// Assignment operator from base class
ColorMono& operator= ( const Color& color_ );
};
</pre>
<h3><a name="ColorHSL"></a>ColorHSL</h3>
<p>Representation of a color in Hue/Saturation/Luminosity (HSL) colorspace.</p>
<pre class="code">
class ColorHSL : public Color
{
public:
ColorHSL ( double hue_, double saturation_, double luminosity_ );
ColorHSL ( void );
ColorHSL ( const Color & color_ );
/* virtual */ ~ColorHSL ( );
void hue ( double hue_ );
double hue ( void ) const;
void saturation ( double saturation_ );
double saturation ( void ) const;
void luminosity ( double luminosity_ );
double luminosity ( void ) const;
// Assignment operator from base class
ColorHSL& operator= ( const Color& color_ );
};
</pre>
<h3><a name="ColorYUV"></a>ColorYUV</h3>
<p>Representation of a color in YUV colorspace (used to encode color for television transmission).</p>
<p>Argument ranges:</p>
<dl>
<dd> Y: 0.0 through 1.0</dd>
<dd> U: -0.5 through 0.5</dd>
<dd> V: -0.5 through 0.5</dd>
</dl>
<pre class="code">
class ColorYUV : public Color
{
public:
ColorYUV ( double y_, double u_, double v_ );
ColorYUV ( void );
ColorYUV ( const Color & color_ );
/* virtual */ ~ColorYUV ( void );
void u ( double u_ );
double u ( void ) const;
void v ( double v_ );
double v ( void ) const;
void y ( double y_ );
double y ( void ) const;
// Assignment operator from base class
ColorYUV& operator= ( const Color& color_ );
};
</pre>
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