HBITMAP to CBitmap?

Justin Houk

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Jan 2, 2001, 11:20:37 PM1/2/01

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Happy New Year everyone!

Thanks to the folks who replied to my previous post. It was very
helpful! Sadly, I'm stuck again and wishing I was working on an
open-source platform like Linux so I could dig into the source code of
the OS and figure out what I'm doing wrong. So sad.

This has got to be simpler than I'm making it, but I can't find a good
way to create a CBitmap member variable using an HBITMAP object. Here's
the code I'm using (I know it's icky):

if ((!(tempGDIBitmap = (HBITMAP)LoadImage(NULL, fileName, IMAGE_BITMAP,
0, 0, LR_LOADFROMFILE))) ||
((tempMFCBitmapPtr = CBitmap::FromHandle(tempGDIBitmap))==NULL))
{
TRACE0("Failed to load bitmap for normal image.\n");
return FALSE; // need this one image
}
tempMFCBitmapPtr->GetBitmap(&tempBitmapStruct);
m_bitmap.CreateBitmapIndirect(&tempBitmapStruct);

Running this through the debugger, I see that tempBitmapStruct has the
proper bmWidth and bmHeight, but bmBits is NULL. Oh, and when I try to
display m_bitmap, it's garbage. I know the problem is in the loading
not the displaying because if I replace this with loading a bitmap from
a resource, everything works great.

Any ideas?

Thanks in advance!!!
--Justin

Justin Houk

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Jan 3, 2001, 6:14:22 PM1/3/01

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Well, I've spent a few more hours trying to get this to work, but to no
avail. Please tell me it's not impossible to load a CBitmap from a
file. This is crazy! :(

I realized I could make the code snipped clearer if I took out some
error checking. Here it is:

tempGDIBitmap = (HBITMAP)LoadImage(NULL, fileName, IMAGE_BITMAP,

0, 0, LR_LOADFROMFILE);
tempMFCBitmapPtr = CBitmap::FromHandle(tempGDIBitmap);
tempMFCBitmapPtr->GetBitmap(&tempBitmapStruct);
m_bitmap.CreateBitmapIndirect(&tempBitmapStruct);

I'm creating a child class of CBitmapButton, so m_bitmap has to be a
CBitmap; it can't be a CBitmap*.

Is it possible that I have to provide an HINSTANCE as the first
parameter of LoadImage(), even if I'm loading from a file? If so, does
anyone know how to get the HINSTANCE of an MFC app? All the example
code I've been able to find gets an HINSTANCE from a DLL.

If anyone could spend a minute to explain what I must be missing, it
would really help me out. I'm stuck.

Thanks!
--Justin

Justin Houk

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Jan 4, 2001, 11:10:07 PM1/4/01

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Many thanks to a friend who sent me a friendly email to let me know that
CBitmaps actually DON'T deal with DIBitmaps (that is, bitmaps from
files) very well.

Armed with that information, I ditched the whole "inheriting from
CBitmapButton" paradigm and instead created a parallel class, which used
HBITMAPs instead of CBitmaps. I had used HBITMAPS before in a non-MFC
app, so I knew I could get those to draw to the screen properly.

So all's well? Well, almost. I'm still running into a problem where my
buttons aren't getting refreshed as often as they should. For example,
if I take the dialog I've made, and drag it practially entirely off the
screen, then drag it back on again, all the Windows-drawn dialogs are
redrawn, but mine aren't. It's like the DrawItem() function of my new
class never got called. Has anyone dealt with this problem before
and/or have any hints how I can get DrawItem() called more frequently?

Thankee-sai!
--Justin

Pete Arends

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Jan 5, 2001, 1:22:49 AM1/5/01

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Justin Houk <jhouk@SPAM_SUXwso.williams.edu> wrote in message
news:3A53B2F0.F602CE62@SPAM_SUXwso.williams.edu...

HBITMAP hbmp = (HBITMAP)LoadImage(NULL, filename, IMAGE_BITMAP, 0, 0,
LR_LOADFROMFILE);
CBitmap cbmp;
cbmp.Attach(hbmp);

use AfxGetInstanceHandle() to get HINSTANCE of your app;

Jon White

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Jan 8, 2001, 6:03:33 AM1/8/01

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"Justin Houk" <jhouk@SPAM_SUXwso.williams.edu> wrote in message
news:3A53B2F0.F602CE62@SPAM_SUXwso.williams.edu...

Hello Justin
Try AfxGetInstanceHandle()
Jon