Re: how to save a bitmap to gif file with transparent backgraound? - C / C++ / MFC Discussion Boards

Federico Milano11-Sep-06 9:52

11-Sep-06 9:52

Hi,

I'm having some problems with DLLs and templates.
The thing is that I have found almost no info on the web, specially about warning C4251 (there's an article, but it doesn't
answer the question I have). The thing is, I have these modules:

A.dll
B.dll (Uses A.dll)
C.dll (Uses A.dll and B.dll)
D.lib (A static library that uses A.dll and C.dll)
E.exe, the executable (uses A and D)

I have a template in A. The thing is that I have found the warning C4251 when I was compiling the template in A, so I instantiated
the whole template and exported it (and dllimported when I was compiling a module other than A (all of this in the header
file, where the template is defined)). An error
arises when I'm linking E.exe, saying that I have duplicate symbols: the member functions of the template in A. The paradox here
is that if I clean all the explicit instantiations of the template and the dllexports/dllimports everything works fine! (It gives me
the C4251 warning when compiling, but it works fine). My questions are: is it necessary to explicitly instatiate the whole template,
, export it and import it when compiling other module? Or is it enough to leave an instantiation per translation unit, given that the dlls and exes are compiled
with the same compiler flags? In this case, what happens with static variables? Is the linker clever enough to use the same static
variable for the different instatiations?

any hint will be very appreciated

Thanks,

Federico

Re: Templates and dynamic libraries

Zac Howland11-Sep-06 10:22

Zac Howland

11-Sep-06 10:22

Because of the nature of templates, you can't put them in DLLs to be exported. Templates are placeholders. For example, when you write vector<MyClass> myVector; the compiler sees it and creates that vector. The vector of MyClass objects is then a specific type. When you just have the template definition, there is no type associated with it yet.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Re: Templates and dynamic libraries

Federico Milano11-Sep-06 10:27

Federico Milano

11-Sep-06 10:27

Of course, you're right; but in A I'm using the template as a member of a class thats exported, so the template (at least some of its method) are instantiated in A.dll
This template is also used in E.exe and in B.dll. I think that the question in the original mail is still valid...

Re: Templates and dynamic libraries

Zac Howland11-Sep-06 10:33

Zac Howland

11-Sep-06 10:33

Sorry, I misunderstood your question. While I don't like using this solution much, you might end up having to use #pragma warning(disable...) for that warning.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Re: Templates and dynamic libraries

Jörgen Sigvardsson11-Sep-06 11:55

Jörgen Sigvardsson

11-Sep-06 11:55

You have two solutions:
1) Use the pimpl idiom
2) Use the Microsoft export "hack"

1) By pimpl idiom I mean:

// Header
class Class {
   struct Pimpl;
   Pimpl* m_pimpl;
public:
   Class();
   ~Class();
   void SetX(int x);
};
  
// Source file
struct Class::Pimpl { int x; }
 
Class::Class() : m_pimpl(new Pimpl)
{
}
 
Class::~Class() { delete m_pimpl; }
  
void Class::SetX(int x) { m_pimpl->x = x; }

That also has the benefit to minimize dependencies between sourcefiles. If you change a data member, only the .cpp containing the Pimpl struct will be recompiled - not all other files which include the header file. More on this idiom can be read here: http://www.gotw.ca/gotw/028.htm[^]

2) This hack is non portable AFAIK. On the other hand, exporting C++ classes is non portable as well, so I guess it's not a problem for you. You can read more about it here: http://support.microsoft.com/kb/q168958/[^]

--
Torn from tomorrow's headlines

Re: Templates and dynamic libraries

cmk11-Sep-06 17:43

cmk

11-Sep-06 17:43

As mentioned, the MS hack is the easiest (though non-portable) way.

e.g.

MyArrayT.h (example template class)
template<class TT> class MyArrayT {...};

MyTempExp.h (not really needed)
typedef MyArrayT<long> MyArrayLong;

MyTempExp.cpp (this is the important part)
template class __declspec(dllexport) MyArrayT<long>;

This will create exports of all methods/data for MyArrayT<long>.

...cmk

Save the whales - collect the whole set

how to save a bitmap to gif file with transparent backgraound?

includeh1011-Sep-06 9:03

includeh10

11-Sep-06 9:03

I need source-code or tool to save bitmap buffer to gif file programmatically in VC app, user can specify transparent background color when saving.

which class or tool can help to do that?

Re: how to save a bitmap to gif file with transparent backgraound?

mostafa_pasha11-Sep-06 9:31

mostafa_pasha

11-Sep-06 9:31

Best option i think you use GDI+!
so first try,
http://www.codeproject.com/vcpp/gdiplus/gdi__and_mfc.asp
for initalize GDI+ then try to search MSDN , encoder & decoder :
for example if you wanna convert bmp to gif this code help you:

<br />
INT GetEncoderClsid(const WCHAR* format, CLSID* pClsid)  // helper function<br />
{<br />
UINT  num = 0;          // number of image encoders<br />
   UINT  size = 0;         // size of the image encoder array in bytes<br />
<br />
   ImageCodecInfo* pImageCodecInfo = NULL;<br />
<br />
   GetImageEncodersSize(&num, &size);<br />
   if(size == 0)<br />
      return -1;  // Failure<br />
<br />
   pImageCodecInfo = (ImageCodecInfo*)(malloc(size));<br />
   if(pImageCodecInfo == NULL)<br />
      return -1;  // Failure<br />
<br />
   GetImageEncoders(num, size, pImageCodecInfo);<br />
<br />
   for(UINT j = 0; j < num; ++j)<br />
   {<br />
      if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )<br />
      {<br />
         *pClsid = pImageCodecInfo[j].Clsid;<br />
         free(pImageCodecInfo);<br />
         return j;  // Success<br />
      }    <br />
   }<br />
<br />
   free(pImageCodecInfo);<br />
   return -1;  // Failure<br />
<br />
}<br />
<br />
<br />
<br />
   CLSID   encoderClsid;<br />
   Status  stat;<br />
   Image*   image = new Image(L"Bird.bmp");<br />
<br />
   // Get the CLSID of the PNG encoder.<br />
   GetEncoderClsid(L"image/gif", &encoderClsid);<br />
<br />
   stat = image->Save(L"Bird.gif", &encoderClsid, NULL);<br />
<br />
   <br />
<br />
   delete image;<br />
<br />

Re: how to save a bitmap to gif file with transparent backgraound?

mostafa_pasha11-Sep-06 9:36

mostafa_pasha

11-Sep-06 9:36

& for transparent background you can search : ImageAttributes class & ColorMatrix class
first create ColorMatrix ! then with SetColorMatrix assign that to instance of ImageAttribute then
draw both of image ! so you can see it transparent background!

Re: how to save a bitmap to gif file with transparent backgraound?

Waldermort11-Sep-06 9:33

Waldermort

11-Sep-06 9:33

there are many gif related classes on CP, but most of them are for reading gif files. You will find that saving a gif file is very problematic due to the LZW compression and the patenting issues. Must you use a gif format?

Take a look at this article[^]. Its for displaying gif images to a CStatic control. But within the source code are functions for reading a gif directly from the file. You could try reverse engineering it to save instead.

Re: how to save a bitmap to gif file with transparent backgraound?

C^hris L^osinger11-Sep-06 9:57

C^hris L^osinger

11-Sep-06 9:57

waldermort wrote:
You will find that saving a gif file is very problematic due to the LZW compression and the patenting issues.

all of the relevant LZW patents expired years ago.

image processing | blogging

Re: how to save a bitmap to gif file with transparent backgraound?

Waldermort11-Sep-06 19:23

Waldermort

11-Sep-06 19:23

Oh, really? I didn't realize. So I'm guessing there are no reprocussions to loading and saving gif files now?

Re: how to save a bitmap to gif file with transparent backgraound?

C^hris L^osinger12-Sep-06 1:00

C^hris L^osinger

12-Sep-06 1:00

waldermort wrote:
So I'm guessing there are no reprocussions to loading and saving gif files now?

that's right

image processing | blogging

Custom Wizard issues

the_jebus11-Sep-06 8:47

the_jebus

11-Sep-06 8:47

I'm making a custom wizard to make a DLL project. I'm having a simple problem. I create 2 files, a header and a cpp file. In the project that the wizard creates, I want these files to end up in the Project's 'Source Files' folder. This isn't a physical directory on the disk, mind you. IOW, looking into the .vcproj file for the project, scanning down to the directory structure i'm finding this:

<br />
...<br />
< Filter<br />
        Name="Source Files"<br />
        Filter="txt"><br />
< /Filter><br />
< File<br />
        RelativePath=".\PlugInImpl.h"><br />
< /File><br />
< File<br />
        RelativePath=".\PlugInImpl.cpp"><br />
< /File><br />
...<br />

when what i want to see is this:

<br />
...<br />
< Filter<br />
        Name="Source Files"<br />
        Filter="txt"><br />
        < File<br />
                RelativePath=".\PlugInImpl.h"><br />
        < /File><br />
        < File<br />
                RelativePath=".\PlugInImpl.cpp"><br />
        < /File><br />
< /Filter><br />
...<br />

Re: Custom Wizard issues

the_jebus11-Sep-06 8:49

the_jebus

11-Sep-06 8:49

hmm the code snippet didn't come out like i wanted too there. well, you get my drift hopefully. i need the File elements to be nested in the Filter element. is this done through the javascript file in my custom project? if so, how?

memory allocation question

KellyR11-Sep-06 8:36

KellyR

11-Sep-06 8:36

Hi, I have a question about memory allocation for a CSafeArray, and in general.

Let's say I have a local variable defined like this:

void dosomething()
{
CSafeArray data;

data.CreateOneDim(1);
}

So now I've allocated memory for the CSafeArray. Does this mean I have to deallocate that memory once I'm done with it, or will this memory be automatically deallocated after the variable goes out of scope because it's locally defined? I always thought this would allocate heap memory and you'd have to manually deallocate but I just want to make sure.

Thanks!

Kelly Ryan

Re: memory allocation question

Zac Howland11-Sep-06 8:40

Zac Howland

11-Sep-06 8:40

COleSafeArray's destructor takes care of that for you, so long as you haven't detached the SAFEARRAY object from it.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Positioning in file

Monin D.11-Sep-06 8:28

Monin D.

11-Sep-06 8:28

Before now I used: h=open(....- command and seek/tell for positioning inside file
Now I use: hFile=CreateFile(..... command.
How to position inside file? Will seek/tell work ?

Re: Positioning in file

Zac Howland11-Sep-06 8:39

Zac Howland

11-Sep-06 8:39

Monin D. wrote:
How to position inside file? Will seek/tell work ?

No. fopen returns a FILE pointer. CreateFile returns a file HANDLE. Passing a HANDLE to any of the FILE operations will fail.

You can find a list of all the methods you can use with the file HANDLE you get from CreateFile here.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Re: Positioning in file

Michael Dunn11-Sep-06 8:42

Michael Dunn

11-Sep-06 8:42

Call SetFilePointer()

Re: Positioning in file

Monin D.11-Sep-06 9:24

Monin D.

11-Sep-06 9:24

Thank you very much, it helps me.

Re: Positioning in file

mostafa_pasha11-Sep-06 9:41

mostafa_pasha

11-Sep-06 9:41

after use CreateFile that return hFile
you can declare CFile m_fFile(hFile) & then use
m_fFile.Seek....

if you wanna work with in text mode you should use CStdioFile instead
of CFile.

Seprating client area in MDI application.

mostafa_pasha11-Sep-06 8:20

mostafa_pasha

11-Sep-06 8:20

how seprate client area of application from frame window in MDI?
is way is correct sepreate CChildFrame ???
alternative way i hear is :
create window with WS_OVERLAPPED! but when
i try this:

<br />
BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)<br />
{<br />
	cs.style |= WS_OVERLAPPED;<br />
	if( !CMDIFrameWnd::PreCreateWindow(cs) )<br />
		return FALSE;<br />
	// TODO: Modify the Window class or styles here by modifying<br />
	//  the CREATESTRUCT cs<br />
<br />
	return TRUE;<br />
}<br />

there is nothing happen.

Best Regards.
MJM

Re: Seprating client area in MDI application.

Jun Du11-Sep-06 8:57

Jun Du

11-Sep-06 8:57

mostafa_pasha wrote:
seprate client area of application from frame window in MDI?

Please be more specific on what you want to do.

Best,
Jun

Re: Seprating client area in MDI application.

mostafa_pasha11-Sep-06 9:23

mostafa_pasha

11-Sep-06 9:23

my project is MDI !
i have two view class , CStartPageView and CImageProcessingView !
first application execute OnDraw of CStartPageView because i create document
when OnFileNew fucntion run i create some object as CImagePorcessingView.when create new
page something that i use in CStartPageView::OnDraw show in client area of CImageProcessingView.
i mean every thing i draw in page has affect in another page!although the client area (to view class) is seperable.

<br />
// in CWinApp::InitInstance<br />
// i create to document template :<br />
m_pDocTemplate = new CMultiDocTemplate(<br />
		IDR_ImageProcessingTYPE,<br />
		RUNTIME_CLASS(CImageProcessingDoc),<br />
		RUNTIME_CLASS(CChildFrame), // custom MDI child frame<br />
		RUNTIME_CLASS(CImageProcessingView));<br />
	if (!m_pDocTemplate)<br />
		return FALSE;<br />
	AddDocTemplate(m_pDocTemplate);<br />
<br />
	m_pDocTemplateStartPage = new CMultiDocTemplate(<br />
		IDR_ImageProcessingTYPE,<br />
		RUNTIME_CLASS(CImageProcessingDoc),<br />
		RUNTIME_CLASS(CChildFrame),<br />
		RUNTIME_CLASS(CStartPageView));<br />
	if (!m_pDocTemplateStartPage)<br />
		return FALSE;<br />
	AddDocTemplate(m_pDocTemplateStartPage);<br />
<br />
in OnFileNew:<br />
//create document that class view is CStartPageView <br />
CDocument* pDoc = m_pDocTemplateStartPage->OpenDocumentFile(NULL);<br />
<br />
<br />
// & for CImageProcessingView is <br />
pDocTemplate->OpenDocument(BULL);<br />
<br />

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