VC + + Load Transparent PNG image method-gdi+ and CImage two kinds

Reprinted from: http://blog.csdn.net/zhongbin104/article/details/8730935

First look at the GDI + method
Method 1:

 1.gdi+ PNG image with transparent layer (alpha)

StdAfx join as follows:

 

#include//Initialize the COM port #include "GdiPlus.h" using namespace GdiPlus; #pragma comment (lib, "Gdiplus.lib")

 

Start initialization:
In the declaration of the App Class (. h), add:

 

ULONG_PTR M_gdiplustoken;

  

InitInstance () added://If there is no usingnamespace Gdiplus; Add Gdiplus in front::

 

Gdiplusstartupinput Gdiplusstartupinput; Gdiplusstartup (&m_gdiplustoken, &gdiplusstartupinput, NULL);

 

Heavy-duty ExitInstance, added Gdiplusshutdown (M_gdiplustoken);

 

int cxxxapp::exitinstance () {//TODO: Add private code here and/or call base class Gdiplusshutdown (M_gdiplustoken); return CWinApp::ExitInstance () ;}

 

The process of displaying the picture is as follows

CClientDC *PDC = new CClientDC (GetDlgItem (idc_static_pic)); CRect rect; GetDlgItem (idc_static_pic)->getwindowrect (&rect); Graphics graphics (PDC->M_HDC); Create a GDI + Graphics object image Image (_t ("1.png")); Construct an image graphics. DrawImage (&image, 0, 0, image. GetWidth (), image. GetHeight ()); Delete PDC;

This is to display the picture with GDI +.

 2.CImage draw a PNG image with alpha transparent layers MFC's own CImage can also be displayed, but a little conversion to get a normal PNG image with the alpha channel! convert one time before drawing, where image is an object of CImage

if (image.getbpp () = = 32)//Confirm that the image contains alpha channel {int i; Int J; for (i = 0; i < image.getwidth (); i++) {for (j = 0; J < i Mage. GetHeight ();  J + +) {byte *pbyte = (BYTE *) image.getpixeladdress (i, J);p byte[0] = pbyte[0] * pbyte[3]/255;pbyte[1] = pbyte[1] * Pbyte[3] /255;pbyte[2] = pbyte[2] * pbyte[3]/255;}}}

Here's how:

 

HWND hwnd = GetSafeHwnd (); Gets the HWND of the window:: InvalidateRect (hwnd, NULL, True); Or:: InvalidateRect (hwnd, NULL, FALSE); :: UpdateWindow (HWND); If you do not want to use the original drawing to remove the picture, you can delete the above three-segment CDC *PDC = GetDC (); CImage Image;image. Load (strpath);  if (Image.isnull ()) {MessageBox (_t ("Not loaded successfully")); return-1;} if (image.getbpp () = = 32)//Confirm that the image contains alpha channel {int i; Int J; for (i = 0; I < image.getwidth (); i++) {for (j = 0, J < Image.getheight (); j + +) {byte *pbyte = (BYTE *) image.getpixeladdress (i, J);p byte[0] = pbyte[0] * p BYTE[3]/255;pbyte[1] = pbyte[1] * pbyte[3]/255;pbyte[2] = pbyte[2] * pbyte[3]/255;}}} Image.draw (PDC->M_HDC, 0, 0); Image. Destroy (); ReleaseDC (PDC);

The internal framework of the code is the image of the re-processing, the original was modified, so that the more normal, the code is measured as followspost-Drawing effects 3. If the picture is in a resource, the loading method is different. This requires two functions,for GDI + as follows: 

BOOL Imagefromidresource (UINT nID, LPCTSTR str,image *&pimg) {hinstance hInst = AfxGetResourceHandle (); Hrsrc hrsrc =:: FindResource (Hinst,makeintresource (NID), STR); Type if (!HRSRC) return FALSE; Load resource into memory DWORD len = Sizeofresource (HInst, HRSRC); byte* lprsrc = (byte*) loadresource (HInst, HRSRC); if (!LPRSRC) return FALSE; Allocate global memory on which to create stream hglobal M_hmem = GlobalAlloc (gmem_fixed, Len); byte* Pmem = (byte*) globallock (M_HMEM); memcpy (Pmem,lprsrc,len); GlobalUnlock (M_HMEM); istream* pstm; CreateStreamOnHGlobal (m_hmem,false,&pstm); Load from Stream Pimg=gdiplus::image::fromstream (pstm); Free/release stuff Pstm->release (); FreeResource (LPRSRC); GlobalFree (M_HMEM); return TRUE;}

 the code that loads the picture then changes to:

CClientDC *PDC = new CClientDC (GetDlgItem (idc_static_pic)); CRect rect; GetDlgItem (idc_static_pic)->getwindowrect (&rect); Graphics graphics (PDC->M_HDC); Create a GDI + Graphics object Image *pimage; Construct an image Imagefromidresource (idb_png1,_t ("PNG"), Pimage), graphics. DrawImage (pimage, 0, 0,pimage->getwidth (), Pimage->getheight ()); Delete PDC;

    the following functions are required when using CImage :  

 bool Loadimagefromresource (CImage *pimage, UINT nresid,lpctstr Lptyp) {if (pImage = = NULL) return False;pimage->destroy (); Find resources Hrsrc HRSRC =:: FindResource (AfxGetResourceHandle (), Makeintresource (NRESID), Lptyp); if (hrsrc = = NULL) return false; Load Resources Hglobal Himgdata =:: LoadResource (AfxGetResourceHandle (), HRSRC); if (Himgdata = = NULL) {:: FreeResource (Himgdata); return false;}//Lock the specified resource in memory lpvoid LPVOID =:: Lockresource (Himgdata); Lpstream PStream = Null;dword dwsize =:: Sizeofresource (AfxGetResourceHandle (), HRSRC); Hglobal hnew =:: GlobalAlloc (GHND, dwsize); Lpbyte lpbyte = (LPBYTE):: GlobalLock (Hnew);:: memcpy (Lpbyte, LPVOID, dwsize); Unbind the specified resource in memory:: GlobalUnlock (Hnew); Creates a stream object from the specified memory HRESULT HT =:: CreateStreamOnHGlobal (Hnew, TRUE, &pstream); if (HT! = S_OK) {GlobalFree (hnew);} else {//Load Picture pimage->load (PStream); GlobalFree (hnew);} Release resources:: FreeResource (Himgdata); return true;}  

 the code to load the picture is as follows:

HWND hwnd = GetSafeHwnd (); Gets the HWND of the window:: InvalidateRect (hwnd, NULL, True); Or:: InvalidateRect (hwnd, NULL, FALSE); :: UpdateWindow (HWND); CDC *PDC = GetDC (); CImage Image; Loadimagefromresource (&image,idb_png1,_t ("PNG"));  if (Image.isnull ()) {MessageBox (_t ("Not loaded successfully")); return;} if (image.getbpp () = = 32)//Confirm that the image contains alpha channel {int i; Int J; for (i=0; I<image.getwidth (); i++) = "" "{=" "<span=" ">for (j=0; J<image.getheight (); j + +) =" "" {= "" byte= "" *pbyte= "(byte" *) Image.getpixeladdress (i,= "" j); = "" pbyte[<span= "" >0] = pbyte[0] * pbyte[3]/255;pbyte[1] = pbyte[1] * PByte[3]/25 5;PBYTE[2] = pbyte[2] * pbyte[3]/255;}}} Image.draw (pdc->m_hdc,0,0); Image. Destroy (); ReleaseDC (PDC);

  otherNote that it is best to put the drawing in the OnPaint message response, otherwise, the ONSIZE message triggers OnPaint may erase all previous drawings when redrawn

VC + + Load Transparent PNG image method-gdi+ and CImage two kinds