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
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, see PALETTEENTRY in the Windows SDK.
See also
MFC Sample DIBLOOK
CGdiObject Class
Hierarchy Chart
CPalette::GetPaletteEntries
CPalette::SetPaletteEntries
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