CImage Class
CImage provides enhanced bitmap support, including the ability to load and save images in JPEG, GIF, BMP, and Portable Network Graphics (PNG) formats.
class CImage
Remarks
CImage takes bitmaps that are either device-independent bitmap (DIB) sections or not; however, you can use Create or CImage::Load with only DIB sections. You can attach a non-DIB section bitmap to a CImage object using Attach, but then you cannot use the following CImage methods, which support only DIB section bitmaps:
To determine if an attached bitmap is a DIB section, call IsDibSection.
Hinweis
Note In Visual Studio .NET 2003, this class keeps a count of the number of CImage objects created. Whenever the count goes to 0, the function GdiplusShutdown is automatically called to release resources used by GDI+. This ensures that any CImage objects created directly or indirectly by DLLs are always destroyed properly and that GdiplusShutdown is not called from DllMain.
Hinweis
Using global CImage objects in a DLL is not recommended. If you need to use a global CImage object in a DLL, call CImage::ReleaseGDIPlus to explicitly release resources used by GDI+.
CImage cannot be selected into a new CDC. CImage creates its own HDC for the image. Because an HBITMAP can only be selected into one HDC at a time, the HBITMAP associated with the CImage cannot be selected into another HDC. If you need a CDC, retrieve the HDC from the CImage and give it to CDC::FromHandle.
Example
// Get a CDC for the image
CDC* pDC = CDC::FromHandle(m_myImage.GetDC());
// Use pDC here
pDC->Rectangle(0, 40, 100, 50);
m_myImage.ReleaseDC();
When you use CImage in an MFC project, note which member functions in your project expect a pointer to a CBitmap object. If you want to use CImage with such a function, like CMenu::AppendMenu, use CBitmap::FromHandle, pass it your CImage HBITMAP, and use the returned CBitmap*.
void CMyDlg::OnRButtonDown(UINT nFlags, CPoint point)
{
UNREFERENCED_PARAMETER(nFlags);
CBitmap* pBitmap = CBitmap::FromHandle(m_myImage);
m_pmenuPop->AppendMenu(0, ID_BMPCOMMAND, pBitmap);
ClientToScreen(&point);
m_pmenuPop->TrackPopupMenu(TPM_RIGHTBUTTON | TPM_LEFTALIGN, point.x,
point.y, this);
}
Through CImage, you have access to the actual bits of a DIB section. You can use a CImage object anywhere you previously used a Win32 HBITMAP or DIB section.
Hinweis
The following CImage methods have limitations on their use:
Method |
Limitation |
|---|---|
Works with only Windows NT 4.0 or later. Will not work on applications running on Windows 95/98 or later. |
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Works with only Windows NT 4.0 or later. Will not work on applications running on Windows 95/98 or later. |
|
Works with only Windows 2000, Windows 98, and later systems. |
|
Works with only Windows 2000, Windows 98, and later systems. |
|
Supports transparency with only Windows 2000, Windows 98, and later systems. |
See CImage Limitations with Earlier Operating Systems for more detailed information about the limitations on these methods.
You can use CImage from either MFC or ATL.
Hinweis
When you create a project using CImage, you must define CString before you include atlimage.h. If your project uses ATL without MFC, include atlstr.h before you include atlimage.h. If your project uses MFC (or if it is an ATL project with MFC support), include afxstr.h before you include atlimage.h. Likewise, you must include atlimage.h before you include atlimpl.cpp. To accomplish this easily, include atlimage.h in your stdafx.h.
Requirements
Header: atlimage.h
See Also
Concepts
MMXSwarm Sample: Demonstrates CImage and Visual C++ MMX Support
SimpleImage Sample: Loads, Resizes, Converts, and Saves Images