BitBlt( HDC hdcDest, // handle to destination DC int nXDest, // x-coord of destination upper-le

BitBlt

The BitBlt function performs a bit-block transfer of the color data corresponding to a rectangle of pixels from the specified source device context into a destination device context.

BOOL BitBlt(  HDC hdcDest, // handle to destination DC  int nXDest,  // x-coord of destination upper-left corner  int nYDest,  // y-coord of destination upper-left corner  int nWidth,  // width of destination rectangle  int nHeight, // height of destination rectangle  HDC hdcSrc,  // handle to source DC  int nXSrc,   // x-coordinate of source upper-left corner  int nYSrc,   // y-coordinate of source upper-left corner  DWORD dwRop  // raster operation code);

Parameters

hdcDest

[in] Handle to the destination device context.

nXDest

[in] Specifies the x-coordinate, in logical units, of the upper-left corner of the destination rectangle.

nYDest

[in] Specifies the y-coordinate, in logical units, of the upper-left corner of the destination rectangle.

nWidth

[in] Specifies the width, in logical units, of the source and destination rectangles.

nHeight

[in] Specifies the height, in logical units, of the source and the destination rectangles.

hdcSrc

[in] Handle to the source device context.

nXSrc

[in] Specifies the x-coordinate, in logical units, of the upper-left corner of the source rectangle.

nYSrc

[in] Specifies the y-coordinate, in logical units, of the upper-left corner of the source rectangle.

dwRop

[in] Specifies a raster-operation code. These codes define how the color data for the source rectangle is to be combined with the color data for the destination rectangle to achieve the final color.

The following list shows some common raster operation codes.ValueDescriptionBLACKNESSFills the destination rectangle using the color associated with index 0 in the physical palette. (This color is black for the default physical palette.)CAPTUREBLTWindows 98/Me, Windows 2000/XP: Includes any windows that are layered on top of your window in the resulting image. By default, the image only contains your window. Note that this generally cannot be used for printing device contexts.DSTINVERTInverts the destination rectangle.MERGECOPYMerges the colors of the source rectangle with the brush currently selected inhdcDest, by using the Boolean AND operator.MERGEPAINTMerges the colors of the inverted source rectangle with the colors of the destination rectangle by using the Boolean OR operator.NOMIRRORBITMAPWindows 98/Me, Windows 2000/XP: Prevents the bitmap from being mirrored.NOTSRCCOPYCopies the inverted source rectangle to the destination.NOTSRCERASECombines the colors of the source and destination rectangles by using the Boolean OR operator and then inverts the resultant color.PATCOPYCopies the brush currently selected in hdcDest, into the destination bitmap.PATINVERTCombines the colors of the brush currently selected in hdcDest, with the colors of the destination rectangle by using the Boolean XOR operator.PATPAINTCombines the colors of the brush currently selected in hdcDest, with the colors of the inverted source rectangle by using the Boolean OR operator. The result of this operation is combined with the colors of the destination rectangle by using the Boolean OR operator.SRCANDCombines the colors of the source and destination rectangles by using the Boolean AND operator.SRCCOPYCopies the source rectangle directly to the destination rectangle.SRCERASECombines the inverted colors of the destination rectangle with the colors of the source rectangle by using the Boolean AND operator.SRCINVERTCombines the colors of the source and destination rectangles by using the Boolean XOR operator.SRCPAINTCombines the colors of the source and destination rectangles by using the Boolean OR operator.WHITENESSFills the destination rectangle using the color associated with index 1 in the physical palette. (This color is white for the default physical palette.)

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero.

Windows NT/2000/XP: To get extended error information, call GetLastError.

Remarks

BitBlt only does clipping on the destination DC.

If a rotation or shear transformation is in effect in the source device context,BitBlt returns an error. If other transformations exist in the source device context (and a matching transformation isnot in effect in the destination device context), the rectangle in the destination device context is stretched, compressed, or rotated, as necessary.

If the color formats of the source and destination device contexts do not match, theBitBlt function converts the source color format to match the destination format.

When an enhanced metafile is being recorded, an error occurs if the source device context identifies an enhanced-metafile device context.

Not all devices support the BitBlt function. For more information, see the RC_BITBLT raster capability entry in theGetDeviceCaps function as well as the following functions:MaskBlt, PlgBlt, andStretchBlt.

BitBlt returns an error if the source and destination device contexts represent different devices. To transfer data between DCs for different devices, convert the memory bitmap to a DIB by callingGetDIBits. To display the DIB to the second device, callSetDIBits or StretchDIBits.

ICM: No color management is performed when blits occur.

Example Code

For an example, see Capturing an Image.

Requirements

  Windows NT/2000/XP/Vista: Included in Windows NT 3.1 and later.
  Windows 95/98/Me: Included in Windows 95 and later.
  Header: Declared in Wingdi.h; include Windows.h.
  Library: Use Gdi32.lib.

See Also

Bitmaps Overview, Bitmap Functions GetDeviceCaps,GetDIBits, MaskBlt,PlgBlt, SetDIBits,StretchBlt, StretchDIBits

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Capturing an Image

You can use a bitmap to capture an image, and you can store the captured image in memory, display it at a different location in your application's window, or display it in another window.

In some cases, you may want your application to capture images and store them only temporarily. For example, when you scale or zoom a picture created in a drawing application, the application must temporarily save the normal view of the image and display the zoomed view. Later, when the user selects the normal view, the application must replace the zoomed image with a copy of the normal view that it temporarily saved.

To store an image temporarily, your application must call CreateCompatibleDC to create a DC that is compatible with the current window DC. After you create a compatible DC, you create a bitmap with the appropriate dimensions by calling the CreateCompatibleBitmap function and then select it into this device context by calling theSelectObject function.

After the compatible device context is created and the appropriate bitmap has been selected into it, you can capture the image. TheBitBlt function captures images. This function performs a bit block transfer that is, it copies data from a source bitmap into a destination bitmap. However, the two arguments to this function are not bitmap handles. Instead,BitBlt receives handles that identify two device contexts and copies the bitmap data from a bitmap selected into the source DC into a bitmap selected into the target DC. In this case, the target DC is the compatible DC, so whenBitBlt completes the transfer, the image has been stored in memory. To redisplay the image, callBitBlt a second time, specifying the compatible DC as the source DC and a window (or printer) DC as the target DC.

The following example code, from an application that captures an image of the entire desktop, creates a compatible device context and a bitmap with the appropriate dimensions, selects the bitmap into the compatible DC, and then copies the image using theBitBlt function.

// Create a normal DC and a memory DC for the entire screen. The // normal DC provides a "snapshot" of the screen contents. The // memory DC keeps a copy of this "snapshot" in the associated // bitmap.  hdcScreen = CreateDC("DISPLAY", NULL, NULL, NULL); hdcCompatible = CreateCompatibleDC(hdcScreen);  // Create a compatible bitmap for hdcScreen.  hbmScreen = CreateCompatibleBitmap(hdcScreen,                      GetDeviceCaps(hdcScreen, HORZRES),                      GetDeviceCaps(hdcScreen, VERTRES));  if (hbmScreen == 0)     errhandler("hbmScreen", hwnd);  // Select the bitmaps into the compatible DC.  if (!SelectObject(hdcCompatible, hbmScreen))     errhandler("Compatible Bitmap Selection", hwnd);          // Hide the application window.          ShowWindow(hwnd, SW_HIDE);           //Copy color data for the entire display into a          //bitmap that is selected into a compatible DC.          if (!BitBlt(hdcCompatible,                0,0,                bmp.bmWidth, bmp.bmHeight,                hdcScreen,                0,0,                SRCCOPY))          errhandler("Screen to Compat Blt Failed", hwnd);          // Redraw the application window.          ShowWindow(hwnd, SW_SHOW); 

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Requirements

  Windows NT/2000/XP/Vista: Included in Windows NT 3.1 and later.
  Windows 95/98/Me: Included in Windows 95 and later.
  Header: Declared in Wingdi.h; include Windows.h.
  Library: Use Gdi32.lib.

See Also

Bitmaps Overview, Bitmap Functions GetDeviceCaps,GetDIBits, MaskBlt,PlgBlt, SetDIBits,StretchBlt, StretchDIBits

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