help with stetchblt performance

Hey guys. I am reading in a cdg file (karaoke) for mp3+g playback. I have it all working, but I have one little problem. The cd+g is meant to be played at the size 300 x 216, but I want to go 2x, 3x, or fullscreen of that. Problem is that when I do a stretchblt instead of bitblt it gets really slow

is there some alternative I can use other than stretchblt that will size a 300 x 216 bitmap to double or triple the size without such a performance hit?

Here is some of my code: Is there some way I can make this faster?

Code:

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int THEWIDTH = 600;desired width of bitmap
int THEHEIGHT = 438; desired height of bitmap

BYTE pixles[64800]; //300*216  this holds the image i want to put in the bitmap

CDC* pDC = pKaraokeWindow.m_KaraokeWnd.GetDC();

        CDC memdcX;
    memdcX.CreateCompatibleDC(pDC);

        // Set up a palette


hBitmap = CreateDIBSection(NULL, lpbi, DIB_RGB_COLORS, NULL/*(LPVOID *)&pixels*/, NULL, 0 );

        m_bitmap.DeleteObject();
        m_bitmap.Attach(hBitmap);
        m_bitmap.SetBitmapBits(300*216,&pixels);
       
       
        memdcX.SelectPalette(&m_pPalette, FALSE);
        CBitmap* pBitmap = memdcX.SelectObject(&m_bitmap);


        //pDC->BitBlt(0,0,300,216 ,&memdcX,0,0,SRCCOPY);


        pDC->StretchBlt(0,0,THEWIDTH, THEHEIGHT, &memdcX, 0,0, 300, 216, SRCCOPY);
        memdcX.SelectObject(pBitmap);
        ReleaseDC(pDC);

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One possible solution is to stretchblt the original bitmap to the compatible DC first. Then bitblt the compatible DC.

Kuphryn

I thought that's what I was doing? Could you post sample code of what you mean?

Thanks,
Greg

The code bitblt to the DC that pDC points to. Is that the device context of the surface you want to draw?

Kuphryn

yes pDC is the device context I want to draw to.

K I changed the code here to stretchblt to the compatible dc and it does go faster, but the pDC is not the correct size!!

the pDC show up at 300x216 even though memdcX is 600x432?? why wouldn't the pDC be 600x432

Code:

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int THEWIDTH = 600;
int THEHEIGHT = 432;
        CDC* pDC = pKaraokeWindow.m_KaraokeWnd.GetDC();

        CDC memdcX;
    memdcX.CreateCompatibleDC(pDC);

        // Set up a palette
       
hBitmap = CreateDIBSection(NULL, lpbi, DIB_RGB_COLORS, NULL/*(LPVOID *)&pixels*/, NULL, 0 );

        m_bitmap.DeleteObject();
        m_bitmap.Attach(hBitmap);
        m_bitmap.SetBitmapBits(300*216,&pixels);
       
       
        memdcX.SelectPalette(&m_pPalette, FALSE);
        CBitmap* pBitmap = memdcX.SelectObject(&m_bitmap);


        memdcX.StretchBlt(0,0,THEWIDTH, THEHEIGHT, &memdcX, 0,0, 300, 216, SRCCOPY);
       
        pDC->BitBlt(0,0,THEWIDTH,THEHEIGHT ,&memdcX,0,0,SRCCOPY);


        //pDC->StretchBlt(0,0,THEWIDTH, THEHEIGHT, &memdcX, 0,0, 300, 216, SRCCOPY);
        memdcX.SelectObject(pBitmap);
        ReleaseDC(pDC);

                PeekAndPump();
                Sleep(1);

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