About StretchDIBits

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Recently Having Readen Code About How to Show BMP By Operating Pixel,I
don't understand codes about Parameter(lpBits).Code As Below：

**
lpBuf=(LPBYTE)GlobalAlloc(GPTR,sizeof(BITMAPINFO)+255*sizeof(RGBQUAD)+512*512+32*32*5);
lpDIB=(LPBITMAPINFO)lpBuf;
lpRGB=(RGBQUAD*)(lpBuf+sizeof(BITMAPINFOHEADER));
lpScreen=lpBuf+sizeof(BITMAPINFOHEADER)+255*sizeof(RGBQUAD);
for (int i=0;i<5;i++)
lpChr[i]=lpScreen+512*512+32*32*i;

miHeader.biBitCount=8;
lpRGB[0].rgbRed=0;
lpRGB[0].rgbGreen=0;
lpRGB[0].rgbBlue=0;
lpRGB[1].rgbRed=128;
lpRGB[1].rgbGreen=128;
lpRGB[1].rgbBlue=128;
***

By Operating lpBuf(32*32*5),BMP Picture Changed,
I Want to know Funciton of lpBuf(32*32*5)

Posted 25-Jan-10 3:35am

yingkou

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3 solutions

Solution 2

To Above：
>In order to do that, you need to allocate memory for each pixel
> and the desired color depth of that image. That's what the 32*32*5 does.
Could You Tell Me How Much Is That Image(32*32?) and The depth Is 5?

Posted 25-Jan-10 3:54am

yingkou

Solution 3

It isn't very easy to understand why from the context, but the 32*32*5 looks like it is allocating extra memory after the bitmap for use as something else. From the variable name, I would guess it is for 5 32*32 "characters".

The 512*512 will be the size of the bitmap itself, using a 8-bit palette.

255*sizeof(RGBQUAD) is the memory for the palette - the BITMAPINFO structure contains the first RGBQUAD, which is why the 255 instead of 256.

Posted 25-Jan-10 21:32pm

Graham Breach

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#realJSOP · Accepted Answer · 2010-01-25T03:44:00

Solution 1

You're allocating memory for the image. In order to do that, you need to allocate memory for each pixel and the desired color depth of that image. That's what the 32*32*5 does.

Posted 25-Jan-10 3:44am

#realJSOP