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GDI+: Storing content of the Clipboard to a bitmap file

Short description:

Based on GdiPlus class, this code shows how to retrieve an image stored on the clipboard and save it to a graphics file in one of GDI+ supported formats, BMP, GIF. PNG, TIFF, JPEG.

Before you begin:

The code is based on custom GDI+ class. Download the class module first and save it in gdiplus.prg file.

Related code samples:

Code:

SET PROCEDURE TO gdiplus ADDITIVE
#DEFINE CF_BITMAP 2
#DEFINE CF_DIB    8
DO decl

IF IsClipboardFormatAvailable(CF_DIB)=0
	= MESSAGEBOX("No image data found stored " +;
		"on the clipboard.   ")
	RETURN
ENDIF

* an instance of gdiplusinit should be created before
* and released after using any of gdi+ objects
PRIVATE gdiplus As gdiplusinit, img As gdibitmap
gdiplus = CREATEOBJECT("gdiplusinit")

= OpenClipboard(0)

LOCAL bmp As gdibitmap, hBitmap, hDib, lResult
hBitmap = GetClipboardData(CF_BITMAP)
hDib = GetClipboardData(CF_DIB)
bmp = CREATEOBJECT("gdibitmap")

* use either of two ways to create an instance
* of the gdibitmap object
*lResult = bmp.CreateFromHBITMAP(hBitmap)
lResult = bmp.CreateFromBITMAPINFO(hDib)

IF lResult
* make sure the target folder is valid
* uncomment one or more lines with savetofile
*!*		bmp.savetofile("c:\temp\tmp.jpg")
*!*		bmp.savetofile("c:\temp\tmp.gif")
*!*		bmp.savetofile("c:\temp\tmp.bmp")
*!*		bmp.savetofile("c:\temp\tmp.tif")
*!*		bmp.savetofile("c:\temp\tmp.png")
ENDIF

= CloseClipboard()
* end of main

PROCEDURE decl
	DECLARE INTEGER CloseClipboard IN user32
	DECLARE INTEGER OpenClipboard IN user32 INTEGER hwnd
	DECLARE INTEGER GetClipboardData IN user32 INTEGER uFormat

	DECLARE INTEGER IsClipboardFormatAvailable IN user32;
		INTEGER wFormat

Listed functions:

CloseClipboard
GetClipboardData
IsClipboardFormatAvailable
OpenClipboard

Comment:

When an image is copied, most likely it creates on the clipboard at least three different blocks of data:

  • Bitmap handle (CF_BITMAP)
  • BITMAPINFO structure (CF_DIB)
  • BITMAPV5HEADER structure (CF_DIBV5)

This code above retrieves data in CF_DIB format from the clipboard and passes it to the GdipCreateBitmapFromGdiDib function to create an instance of GDI+ bitmap object. This newly created object can be saved to a file, printed or painted on a window.

The GetClipboardData returns a pointer to a memory object containing a BITMAPINFO structure followed by the bitmap bits.

There is a simplification in the way the code treats the BITMAPINFO data. For some display resolutions, like 1, 4, 8 and rarely 16 bits per pixel, the BITMAPINFO structure may contain a color table. If you are able to use GDI+ and Visual FoxPro, most likely your display resolution does not require a presence of such color table in the BITMAPINFO structure. That is how this structure is believed to contain only 40 bytes occupied by BITMAPINFOHEADER data.

Same way the GetClipboardData call with CF_BITMAP as input parameter can retrieve a bitmap handle. This handle then can be passed to the GdipCreateBitmapFromHBITMAP function to create an instance of GDI+ bitmap object. This newly created object can be saved to a file, printed or painted on a window.