MFC loads PNG images and implements double buffering

Because PNG contains an alpha channel, unlike bitmap, it is handled in MFC using the CImage class, typically using the load and draw member functions.

So the title of the discussion can be further explained as, using CImage to achieve double buffering.

The usual double-buffering method is (the function of the message function afx_msg BOOL onerasebkgnd (cdc* PDC) is modified to return TRUE first):

CDC MEMDC; CBitmap bmp;bmp. CreateCompatibleBitmap (pdc,window_width,window_height); Memdc.createcompatibledc (PDC); MemDC.SelectObject (& BMP);//drawing code BMP. DeleteObject (); Memdc.deletedc ();

CImage can load the picture through the load member function and draw the picture onto the DC via the draw member function.

The draw member function is prototyped as a bool Draw (HDC hdestdc, ...), which also needs to get the specified DC, but flashes when a picture is drawn to the DC on one sheet.

Because the idea of double buffering is--draw the diagram first, then copy the past uniformly.

So, the solution is to stick all the pictures on the same CImage object, then unify and then call the draw member function to draw to the DC (if there are other drawing operations in addition to the picture, the DC should be MEMDC). The following function is to draw all pictures first to one picture:

void Crepairclientdlg::showimg (CImage &image, int x, int y) {image. Draw (M_CSCREEN.GETDC (), x, y),//M_csreen for a CImage object M_cscreen.releasedc ();}

Another: the function of loading transparent pictures is as follows:

void Crepairclientdlg::loadimg (CImage &image, CString &strpath) {image. Load (strpath), if (image. IsNull ()) {MessageBox (_t ("Picture not loaded successfully!")); return;} Determine if transparent display is required and do the appropriate processing if (image. GETBPP () = = +) {for (int i = 0; i < image. GetWidth (); ++i) {for (int j = 0; J < image. 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] * PBYT E[3]/255;}}}

　　

MFC loads PNG images and implements double buffering