그리기 함수(점 찍기)

GetPixel

The GetPixel function retrieves the red, green, blue (RGB) color value of the pixel at the specified coordinates.

COLORREF GetPixel(
  HDC hdc,   // handle to device context
  int XPos,  // x-coordinate of pixel
  int nYPos  // y-coordinate of pixel
);
 

Parameters

hdc

Handle to the device context.

nXPos

Specifies the logical x-coordinate of the pixel to be examined.

nYPos

Specifies the logical y-coordinate of the pixel to be examined.

Return Values

The return value is the RGB value of the pixel. If the pixel is outside of the current clipping region, the return value is CLR_INVALID.

Remarks

The pixel must be within the boundaries of the current clipping region.

Not all devices support GetPixel. An application should call GetDeviceCaps to determine whether a specified device supports this function.

QuickInfo

Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in wingdi.h.
Import Library: Use gdi32.lib.

See Also

Bitmaps Overview, Bitmap Functions, GetDeviceCaps, SetPixel 

 

SetPixel

The SetPixel function sets the pixel at the specified coordinates to the specified color.

COLORREF SetPixel(
  HDC hdc,           // handle to device context
  int X,             // x-coordinate of pixel
  int Y,             // y-coordinate of pixel
  COLORREF crColor   // pixel color
);
 

Parameters

hdc

Handle to the device context.

X

Specifies the x-coordinate, in logical units, of the point to be set.

Y

Specifies the y-coordinate, in logical units, of the point to be set.

crColor

Specifies the color to be used to paint the point.

Return Values

If the function succeeds, the return value is the RGB value that the function sets the pixel to. This value may differ from the color specified by crColor; that happens when an exact match for the specified color cannot be found.

If the function fails, the return value is –1.

Windows NT: To get extended error information, call GetLastError.

Remarks

The function fails if the pixel coordinates lie outside of the current clipping region.

Not all devices support the SetPixel function. For more information, see GetDeviceCaps.

QuickInfo

Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in wingdi.h.
Import Library: Use gdi32.lib.

See Also

Bitmaps Overview, Bitmap Functions, GetDeviceCaps, GetPixel, SetPixelV 

SetPixelV

The SetPixelV function sets the pixel at the specified coordinates to the closest approximation of the specified color. The point must be in the clipping region and the visible part of the device surface.

BOOL SetPixelV(
  HDC hdc,           // handle to device context
  int X,             // x-coordinate of pixel
  int Y,             // y-coordinate of pixel
  COLORREF crColor   // new pixel color
);
 

Parameters

hdc

Handle to the device context.

X

Specifies the x-coordinate, in logical units, of the point to be set.

Y

Specifies the y-coordinate, in logical units, of the point to be set.

crColor

Specifies the color to be used to paint the point.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero.

Windows NT: To get extended error information, call GetLastError.

Remarks

Not all devices support the SetPixelV function. For more information, see the description of the RC_BITBLT capability in the GetDeviceCaps function.

SetPixelV is faster than SetPixel because it does not need to return the color value of the point actually painted.

QuickInfo

Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in wingdi.h.
Import Library: Use gdi32.lib.

See Also

Bitmaps Overview, Bitmap Functions, GetDeviceCaps, SetPixel

 

ChildView.cpp