C / C++ / MFC

31-Mar-10 7:31

Ionut Codrut wrote:
My problem is that I do not understand very clear how to convert BITMAPINFOHEADER to BITMAPINFO.

just cast it.

BITMAPINFO *pBMI = (BITMAPINFO *)pBitmapInfoHeader;

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan31-Mar-10 7:58

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 7:58

Thank you Chris for your response!
I try to cast directly as you suggest, but all I've got is just a blank image (so I think the approach is an error)

Acordingly to MSDN http://msdn.microsoft.com/en-us/library/dd318229%28VS.85%29.aspx[^] If you cast the BITMAPINFOHEADER to a BITMAPINFO, the bmiHeader member refers to the BITMAPINFOHEADER and the bmiColors member refers to the first entry in the color table, or the first color mask.

Be aware that if the bitmap uses a color table or color masks, then the size of the entire format structure (the BITMAPINFOHEADER plus the color information) is not equal to sizeof(BITMAPINFOHEADER) or sizeof(BITMAPINFO). You must calculate the actual size for each instance....

So I think we are Close, but no cigar..

Best regards!
Ioan

C^hris L^osinger31-Mar-10 8:06

31-Mar-10 8:06

casting is correct.

but yes, it's also true that you need to find the start of the pixel data in the DIB, and that depends on the number of colors in the palette, any padding, any bitfields masks, etc..

LPBITMAPINFOHEADER      lpbi = (LPBITMAPINFOHEADER)pDIB;
HBITMAP                 hbm;
// how many colors in this DIB?
int nColors = lpbi->biClrUsed ? lpbi->biClrUsed : 
1 << lpbi->biBitCount;
	
BITMAPINFO &bmInfo = *(LPBITMAPINFO)pDIB ;
LPVOID lpDIBBits;
if( bmInfo.bmiHeader.biBitCount > 8 )
{
	lpDIBBits = (LPVOID)((UINT32 *)(bmInfo.bmiColors + 
	bmInfo.bmiHeader.biClrUsed) + 
	((bmInfo.bmiHeader.biCompression == BI_BITFIELDS) ? 3 : 0));
}
else
{
	lpDIBBits = (LPVOID)(bmInfo.bmiColors + nColors);
}

void *ppvBits = NULL;
hbm = CreateDIBSection(hDC,
		   (LPBITMAPINFO)lpbi,
		   DIB_RGB_COLORS,
		   &ppvBits,
		   NULL,
	   0);
		
// copy DIB pixels...
if (ppvBits!=NULL)
{
    memcpy((BYTE *)ppvBits, (BYTE *)lpDIBBits, bmInfo.bmiHeader.biSizeImage);
}

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan31-Mar-10 8:23

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 8:23

Hello Chris!
Thank you very much for your extremely fast response!!!

//This is my starting point:
HBITMAP hbm;
BITMAPINFOHEADER *pHeader;
pHeader = (BITMAPINFOHEADER *)(myImage.bmp.begin() );
// doesn' matter myImage.bmp.begin() is coming from

I need to extract fron this pHeader a HBITMAP to put intr-o a dialog as below:

//This is my end point
m_TestBitButtonCtrl.SetBitmap(hbm);

I do not understand the followings:
1. where pDIB comes from
2. if ia necessary the last function (with copy DIB pixels) for what I need
Ioan

C^hris L^osinger31-Mar-10 8:30

31-Mar-10 8:30

pDIB is your input image. it's a pointer to a DIB, which is a device-independent bitmap: a BITMAPINFOHEADER followed by a palette, followed by the pixel data.

you need the memcpy because CreateDIBSection only allocates the memory for the DIBSection. you need to put your own pixel data into the allocated memory.

and note that a DIBSection is not a standard HBITMAP. you can use a DIBSection as if it was an HBITMAP, and it will work exactly the same as a standard HBITMAP for most uses, but it's not exactly the same thing. see the MSDN for the differences. if you need a standard HBITMAP, you can use CreateDIBitmap instead of CreateDIBSection:

hbm = CreateDIBitmap(hDC,       // handle to device context
(LPBITMAPINFOHEADER)lpbi,       // pointer to bitmap info header 
(LONG)CBM_INIT,                 // initialization flag
lpDIBBits,                      // pointer to initialization data 
(LPBITMAPINFO)lpbi,             // pointer to bitmap info
DIB_RGB_COLORS );               // color-data usage

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan31-Mar-10 8:39

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 8:39

Chris, I'm a newbie to this deep API functions, all the information I've got from an external API is just this BITMAPINFOHEADER* pHeader, nothing more and I need only HBITMAP to extract from them, do not care by which method, my interest is to set a button picture with this bitmap, and that's all!

So let me understand correctly: to obtain the correct HBITMAP do I need extra info, the BITMAPINFOHEADER provideed is not sufficent?

best wishes!
Ioan

C^hris L^osinger31-Mar-10 9:08

31-Mar-10 9:08

Ionut Codrut wrote:
all the information I've got from an external API is just this BITMAPINFOHEADER* pHeader, nothing more

that's all you need.

what happens if you use the code i posted ?

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan31-Mar-10 9:38

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 9:38

I have used your code as below:

BITMAPINFOHEADER *pHeader;
pHeader = (BITMAPINFOHEADER *)(odImage.bmp.begin() );
if(!pHeader)
return TRUE;
HBITMAP hbm;
// how many colors in this DIB?
int nColors = pHeader->biClrUsed ? pHeader->biClrUsed : 1 << pHeader->biBitCount;

BITMAPINFO &bmInfo = *(LPBITMAPINFO)pHeader ;// make cast from BITMAPINFOHEADER!
LPVOID lpDIBBits;
if( bmInfo.bmiHeader.biBitCount > 8 )
{
lpDIBBits = (LPVOID)((UINT32 *)(bmInfo.bmiColors +
bmInfo.bmiHeader.biClrUsed) + ((bmInfo.bmiHeader.biCompression == BI_BITFIELDS) ? 3 : 0));
}
else
{
lpDIBBits = (LPVOID)(bmInfo.bmiColors + nColors);
}

void *ppvBits = NULL;
hbm = CreateDIBSection(NULL,
(LPBITMAPINFO)pHeader,
DIB_RGB_COLORS,
&ppvBits,
NULL,
0);

m_TestBitButtonCtrl.SetBitmap(hbm);

I'm still got a black bitmap, HBITMAP is not NULL (checked with debug!).
Strange!
What I'm wrong?

Ioan

C^hris L^osinger31-Mar-10 9:46

31-Mar-10 9:46

what are the values in the BITMAPINFOHEADER struct ?

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan31-Mar-10 9:58

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 9:58

This is what I've got!

http://www.cnc-router.ro/temp/Screen.JPG[^]

C^hris L^osinger31-Mar-10 10:07

31-Mar-10 10:07

those all look fine.

what happens if you use the CreateDIBitmap function instead of CreateDIBSection ?

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan31-Mar-10 10:22

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 10:22

Chris, the results seem to be the same, a black bitmap. Anyway in both cases it seems that there is something wrong with HBITMAP itself. I have attach a picture for that.
http://www.cnc-router.ro/temp/Screen1.JPG[^]

C^hris L^osinger31-Mar-10 10:30

31-Mar-10 10:30

what do you get if you draw the original DIB (try StretchDIBits)

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan31-Mar-10 10:37

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 10:37

I'm struggle to implement it!
Keep you informed ASAP

bioan31-Mar-10 10:59

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

31-Mar-10 10:59

I try this code:

int iRet = StretchDIBits(NULL,
// destination rectangle
0, 0, bmInfo.bmiHeader.biWidth, bmInfo.bmiHeader.biHeight,
// source rectangle
0, 0, bmInfo.bmiHeader.biWidth, -bmInfo.bmiHeader.biHeight,
ppvBits,
&bmInfo,
DIB_RGB_COLORS,
SRCCOPY);

But the function generates me an errror..

C^hris L^osinger31-Mar-10 16:42

31-Mar-10 16:42

that first parameter has to be a valid DC (NULL is not a valid DC)

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

bioan1-Apr-10 22:50

Re: How to extract the bitmap (HBITMAP) from a BITMAPINFOHEADER variable?

1-Apr-10 22:50

I have checked again CreateDIBitmap and I finally got the correct bitmap displaying on my button, so your code works just perfect!
Thank you very much for your time offered to me!

Best regards!
Ioan

C^hris L^osinger2-Apr-10 1:15

2-Apr-10 1:15

you're welcome!