CreateDIBSection returns NULL.

**SAP_7** · 08-21-2017

Hi,
please help me to resolve the error of createDIBSection returns NULL.
Given below the code before calling the createDIBSection .
I tried to creates a DIB using CreateDIBSection but it returns NULL. GetLastError() returns 0. I could not find out what could be the error.
I think the size of deviceContext is high.I am new to this DIBSection function and not sure how internal function works

Code:


CDC * pSourceDC = AfxGetMainWnd()->GetDC();


BYTE * pDIBbuffer = new BYTE[sizeof(BITMAPINFOHEADER) + 256*sizeof(WORD)];
if (pDIBbuffer == NULL) {  throw; }

BITMAPINFO * pDIB = (BITMAPINFO *)pDIBbuffer;


pDIB->bmiHeader.biSize= sizeof(BITMAPINFOHEADER);
pDIB->bmiHeader.biWidth= m_totalWidth;
pDIB->bmiHeader.biHeight= m_totalHeight;
pDIB->bmiHeader.biPlanes= 1;
pDIB->bmiHeader.biBitCount= 24;          // MUST be 24-bit DIB for JPEG 
pDIB->bmiHeader.biCompression= BI_RGB;
pDIB->bmiHeader.biSizeImage= 0;
pDIB->bmiHeader.biXPelsPerMeter= 0;
pDIB->bmiHeader.biYPelsPerMeter= 0;
pDIB->bmiHeader.biClrUsed= 0;
pDIB->bmiHeader.biClrImportant= 0;
WORD* color = (WORD*) pDIB->bmiColors;

for (i = 0; i < 256; i++)
{
*(color++) = i;
}
    ColorPalette* colorPal = ColorPalette::getInstance();
CPalette* pOldPal = pSourceDC->SelectPalette( &(colorPal->GetWindowPalette()), FALSE);
pSourceDC->RealizePalette();
   HBITMAP hBitmap = CreateDIBSection(pSourceDC->GetSafeHdc(),
pDIB,
DIB_PAL_COLORS,
(void **)&pvBits,// Here's where we put the image
NULL,
0);

Thank you

**SAP_7** · 08-22-2017

Could any of you reply to this since i need to complete this quickly. Despite of being tried for 2 days , I could not understand/find out where is the error

**algorism** · 08-22-2017

24-bit bitmaps don't have a color table.
Either set biBitCount to 8 or get rid of the color table (set bmiColors to NULL).

**SAP_7** · 08-22-2017

Originally Posted by algorism

24-bit bitmaps don't have a color table.
Either set biBitCount to 8 or get rid of the color table (set bmiColors to NULL).

Thank you algorism.
I attempted the both ways.It still returns the NULL.

**algorism** · 08-22-2017

"Attempted the both ways" suggests you're not really thinking.
You have to decide which way you want it.
Let's assume you want a 24-bit bitmap, which is the common case.
So get rid of all of the palette crap.

You also need to change DIB_PAL_COLORS to DIB_RGB_COLORS

You haven't bothered to show how you define pvBits. I wager it's wrong, too, since the rows need to be a multiple of 4.

Try something like this. (I haven't tested it since I don't run Windows anymore.)

Code:

CDC *pSourceDC = AfxGetMainWnd()->GetDC();

BITMAPINFO *pDIB = new BITMAPINFO;
ZeroMemory(pDIB, sizeof(BITMAPINFO));
pDIB->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
pDIB->bmiHeader.biWidth = m_totalWidth;
pDIB->bmiHeader.biHeight = m_totalHeight;
pDIB->bmiHeader.biPlanes = 1;
pDIB->bmiHeader.biBitCount = 24;
pDIB->bmiHeader.biCompression = BI_RGB;

int stride = 3 * m_totalWidth; // 3 bytes per pixel (24-bits)
stride = (stride + 3) & ~3;    // rows are rounded to a multiple of 4

BYTE* bits = new BYTE[stride * m_totalHeight];

HBITMAP hBitmap = CreateDIBSection(
    pSourceDC->GetSafeHdc(),
    pDIB,
    DIB_RGB_COLORS,
    (VOID**)&bits,
    NULL,
    0);

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