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CPalette Class

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The latest version of this topic can be found at CPalette Class.

Encapsulates a Windows color palette.

Syntax

class CPalette : public CGdiObject

Members

Public Constructors

Name Description
CPalette::CPalette Constructs a CPalette object with no attached Windows palette. You must initialize the CPalette object with one of the initialization member functions before it can be used.

Public Methods

Name Description
CPalette::AnimatePalette Replaces entries in the logical palette identified by the CPalette object. The application does not have to update its client area, because Windows maps the new entries into the system palette immediately.
CPalette::CreateHalftonePalette Creates a halftone palette for the device context and attaches it to the CPalette object.
CPalette::CreatePalette Creates a Windows color palette and attaches it to the CPalette object.
CPalette::FromHandle Returns a pointer to a CPalette object when given a handle to a Windows palette object.
CPalette::GetEntryCount Retrieves the number of palette entries in a logical palette.
CPalette::GetNearestPaletteIndex Returns the index of the entry in the logical palette that most closely matches a color value.
CPalette::GetPaletteEntries Retrieves a range of palette entries in a logical palette.
CPalette::ResizePalette Changes the size of the logical palette specified by the CPalette object to the specified number of entries.
CPalette::SetPaletteEntries Sets RGB color values and flags in a range of entries in a logical palette.

Public Operators

Name Description
CPalette::operator HPALETTE Returns the HPALETTE attached to the CPalette.

Remarks

A palette provides an interface between an application and a color output device (such as a display device). The interface allows the application to take full advantage of the color capabilities of the output device without severely interfering with the colors displayed by other applications. Windows uses the application's logical palette (a list of needed colors) and the system palette (which defines available colors) to determine the colors used.

A CPalette object provides member functions for manipulating the palette referred to by the object. Construct a CPalette object and use its member functions to create the actual palette, a graphics device interface (GDI) object, and to manipulate its entries and other properties.

For more information on using CPalette, see Graphic Objects.

Inheritance Hierarchy

CObject

CGdiObject

CPalette

Requirements

Header: afxwin.h

CPalette::AnimatePalette

Replaces entries in the logical palette attached to the CPalette object.

void AnimatePalette(
    UINT nStartIndex,  
    UINT nNumEntries,  
    LPPALETTEENTRY lpPaletteColors);

Parameters

nStartIndex
Specifies the first entry in the palette to be animated.

nNumEntries
Specifies the number of entries in the palette to be animated.

lpPaletteColors
Points to the first member of an array of PALETTEENTRY structures to replace the palette entries identified by nStartIndex and nNumEntries.

Remarks

When an application calls AnimatePalette, it does not have to update its client area, because Windows maps the new entries into the system palette immediately.

The AnimatePalette function will only change entries with the PC_RESERVED flag set in the corresponding palPaletteEntry member of the LOGPALETTE structure that is attached to the CPalette object. See LOGPALETTE in the Windows SDK for more information about this structure.

CPalette::CPalette

Constructs a CPalette object.

CPalette();

Remarks

The object has no attached palette until you call CreatePalette to attach one.

CPalette::CreateHalftonePalette

Creates a halftone palette for the device context.

BOOL CreateHalftonePalette(CDC* pDC);

Parameters

pDC
Identifies the device context.

Return Value

Nonzero if the function is successful; otherwise 0.

Remarks

An application should create a halftone palette when the stretching mode of a device context is set to HALFTONE. The logical halftone palette returned by the CreateHalftonePalette member function should then be selected and realized into the device context before the CDC::StretchBlt or StretchDIBits function is called.

See the Windows SDK for more information about CreateHalftonePalette and StretchDIBits.

CPalette::CreatePalette

Initializes a CPalette object by creating a Windows logical color palette and attaching it to the CPalette object.

BOOL CreatePalette(LPLOGPALETTE lpLogPalette);

Parameters

lpLogPalette
Points to a LOGPALETTE structure that contains information about the colors in the logical palette.

Return Value

Nonzero if successful; otherwise 0.

Remarks

See the Windows SDK for more information about the LOGPALETTE structure.

CPalette::FromHandle

Returns a pointer to a CPalette object when given a handle to a Windows palette object.

static CPalette* PASCAL FromHandle(HPALETTE hPalette);

Parameters

hPalette
A handle to a Windows GDI color palette.

Return Value

A pointer to a CPalette object if successful; otherwise NULL.

Remarks

If a CPalette object is not already attached to the Windows palette, a temporary CPalette object is created and attached. This temporary CPalette object is valid only until the next time the application has idle time in its event loop, at which time all temporary graphic objects are deleted. In other words, the temporary object is valid only during the processing of one window message.

CPalette::GetEntryCount

Call this member function to retrieve the number of entries in a given logical palette.

int GetEntryCount();

Return Value

Number of entries in a logical palette.

CPalette::GetNearestPaletteIndex

Returns the index of the entry in the logical palette that most closely matches the specified color value.

UINT GetNearestPaletteIndex(COLORREF crColor) const;

Parameters

crColor
Specifies the color to be matched.

Return Value

The index of an entry in a logical palette. The entry contains the color that most nearly matches the specified color.

CPalette::GetPaletteEntries

Retrieves a range of palette entries in a logical palette.

UINT GetPaletteEntries(
    UINT nStartIndex,  
    UINT nNumEntries,  
    LPPALETTEENTRY lpPaletteColors) const;

Parameters

nStartIndex
Specifies the first entry in the logical palette to be retrieved.

nNumEntries
Specifies the number of entries in the logical palette to be retrieved.

lpPaletteColors
Points to an array of PALETTEENTRY data structures to receive the palette entries. The array must contain at least as many data structures as specified by nNumEntries.

Return Value

The number of entries retrieved from the logical palette; 0 if the function failed.

CPalette::operator HPALETTE

Use this operator to get the attached Windows GDI handle of the CPalette object.

operator HPALETTE() const;

Return Value

If successful, a handle to the Windows GDI object represented by the CPalette object; otherwise NULL.

Remarks

This operator is a casting operator, which supports direct use of an HPALETTE object.

For more information about using graphic objects, see the article Graphic Objects in the Windows SDK.

CPalette::ResizePalette

Changes the size of the logical palette attached to the CPalette object to the number of entries specified by nNumEntries.

BOOL ResizePalette(UINT nNumEntries);

Parameters

nNumEntries
Specifies the number of entries in the palette after it has been resized.

Return Value

Nonzero if the palette was successfully resized; otherwise 0.

Remarks

If an application calls ResizePalette to reduce the size of the palette, the entries remaining in the resized palette are unchanged. If the application calls ResizePalette to enlarge the palette, the additional palette entries are set to black (the red, green, and blue values are all 0), and the flags for all additional entries are set to 0.

For more information on the Windows API ResizePalette, see ResizePalette in the Windows SDK.

CPalette::SetPaletteEntries

Sets RGB color values and flags in a range of entries in a logical palette.

UINT SetPaletteEntries(
    UINT nStartIndex,  
    UINT nNumEntries,  
    LPPALETTEENTRY lpPaletteColors);

Parameters

nStartIndex
Specifies the first entry in the logical palette to be set.

nNumEntries
Specifies the number of entries in the logical palette to be set.

lpPaletteColors
Points to an array of PALETTEENTRY data structures to receive the palette entries. The array must contain at least as many data structures as specified by nNumEntries.

Return Value

The number of entries set in the logical palette; 0 if the function failed.

Remarks

If the logical palette is selected into a device context when the application calls SetPaletteEntries, the changes will not take effect until the application calls CDC::RealizePalette.

For more information on the Windows structure PALETTEENTRY, see PALETTEENTRY in the Windows SDK.

See Also

MFC Sample DIBLOOK
CGdiObject Class
Hierarchy Chart
CPalette::GetPaletteEntries
CPalette::SetPaletteEntries