Re: compression/Zip problem - C / C++ / MFC Discussion Boards

Re: Why the copy construct of GraphicsPath is protected?

Iain Clarke, Warrior Programmer9-Apr-09 1:45

9-Apr-09 1:45

I imagine it's because GDI classes just wrap a raw handle to the object inside Gdiplus.dll. The constructor creates the handle, and the destructor closes it. As there's no hint of reference counting, copying the classes is just begging for errors.

This protects you.

I've been doing a bunch of GDI+ work recently, and what I did in some code I wrote yesterday was:

BOOL CreateArrowCap (GraphicsPath &path, float fSize)
{
...
}

I used the reference rather than a pointer, as it makes little sense to pass NULL. But it would be valid in other circumstances.

Iain.

In the process of moving to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), give me a job!

compression/Zip problem

chandrakar ashish9-Apr-09 0:01

chandrakar ashish

9-Apr-09 0:01

i want to compress some image file created in my project and store it. for future use and whenever its needed unzipped the stored file.

please any one let me know how i will do that and is it microsoft MFC has provide any API for that.

Thanks in advance.. Smile | :)

Re: compression/Zip problem

Hamid_RT9-Apr-09 0:05

Hamid_RT

9-Apr-09 0:05

See Zip and Unzip in the MFC way. Free source code and ...[^]

Of one Essence is the human race
thus has Creation put the base
One Limb impacted is sufficient
For all Others to feel the Mace
(Saadi )

Re: compression/Zip problem

chandrakar ashish9-Apr-09 1:23

chandrakar ashish

9-Apr-09 1:23

Thank You,
Hamid

That is exactly I am looking for.
Thanks again for your valuable and quick response

Regards,
Ashish Blush | :O

Re: compression/Zip problem

Rajesh R Subramanian9-Apr-09 1:31

Rajesh R Subramanian

9-Apr-09 1:31

Plug: You can please, click the "Good Answer" link on his reply to you.

It is a crappy thing, but it's life -^ Carlo Pallini

Re: compression/Zip problem

chandrakar ashish9-Apr-09 1:39

chandrakar ashish

9-Apr-09 1:39

Ok,

i clicked on the link

Thanks for remind me

Re: compression/Zip problem

Rajesh R Subramanian9-Apr-09 0:44

Rajesh R Subramanian

9-Apr-09 0:44

The only thing that I can think of, from Microsoft, on these lines is the CAB SDK[^]. But I see you are wanting to compress image files, so I do not know what good can cab compression do for you.

There is no standard way of creating a zip compressed file using MFC or Windows API. I believe the .NET framework has this feature though. There is also the LZMA SDK[^] which can compress to .7z format, if you'd like it. The compression would be better than zip (and even rar) and the library works like a charm.

Almost all compression utilities can extract from .7z files, so you don't have to possibly worry on the compatibility front too.

It is a crappy thing, but it's life -^ Carlo Pallini

Re: compression/Zip problem

Divyang Mithaiwala9-Apr-09 0:54

Divyang Mithaiwala

9-Apr-09 0:54

Hi Ashish,

Here you find good library for ZIP/UnZIP uitility.
It is just .cpp & .h files for ZIP & UnZIP utility.

This library is used in any c++ compiler (g++ linux, VC++ eVC++).

Do not trust a computer...
Always check what computer is doing

regards,
Divyang Mithaiwala
Software Engineer

pointer casting

Jorge8-Apr-09 23:48

Jorge

8-Apr-09 23:48

I am trying to cast an int pointer to double pointer, but conversion doesn´t work. I´ve tried c style casting and reinterpret_cast without success. Can anyone help me, please? For instance, how can I make ths work fine:

int a[]={1,2,3,4};
int* b;
double* c;

b=a;
c=(double*)b;

Thanks

Re: pointer casting

CPallini8-Apr-09 23:55

CPallini

8-Apr-09 23:55

Jorge wrote:
how can I make ths work fine:

What does it mean, in your opinion?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: pointer casting

Jorge9-Apr-09 0:07

Jorge

9-Apr-09 0:07

I am not sure what you mean.

Re: pointer casting

CPallini9-Apr-09 0:45

CPallini

9-Apr-09 0:45

The code is working fine, anyway it is not performing a conversion, it is interpreting the raw bits as a double.
You have the following string of bits (only the first two ints of the array matters):

                                 1                                   2
00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010

as a double it is

 00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010
 ^
 0 as sign (first bit on the left), i.e. positive number

 00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010
  ^---------^ 
       0 as exponent with in excess -1023 representation represents denormals when fraction is <> 0
       (as in your case).
 
 00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010
             ^---------------------------------------------------------^
        2^-20 + 2^-51 = 9,5367431685033920985006261616945e-7 as fraction

That gives, for a denormalized number


  fraction * 2^-1021 = 4,2439915839068072135877506064327e-314

Re: pointer casting

Rajesh R Subramanian9-Apr-09 1:19

Rajesh R Subramanian

9-Apr-09 1:19

Good stuff man, my 5. Smile | :)

It is a crappy thing, but it's life -^ Carlo Pallini

Re: pointer casting

CPallini9-Apr-09 1:55

CPallini

9-Apr-09 1:55

Thanks, anyway I'm quite sure there's some mistakes here and there... Roll eyes | :rolleyes:

Re: pointer casting

Rajesh R Subramanian9-Apr-09 2:09

Rajesh R Subramanian

9-Apr-09 2:09

It is a crappy thing, but it's life -^ Carlo Pallini

Re: pointer casting

Jorge9-Apr-09 1:37

Jorge

9-Apr-09 1:37

Hmm, it seems I got my reply. I still have the problem but this makes me afford it in a wiser manner. Thanks so much.

Re: pointer casting

Rajesh R Subramanian9-Apr-09 0:38

Rajesh R Subramanian

9-Apr-09 0:38

What do you mean by "conversion doesn't work"? There's actually no conversion that I can see. If you were wanting to convert the individual int elements of your int array to double, you should do that 'manually'. If you were just intending to change the pointer type, then there shouldn't be any difficulty:

int nArray[] = {1, 2, 3, 4};
double* pDouble = reinterpret_cast<double*>(nArray);
CString szStr;
szStr.Format(_T("%d %d"), *pDouble, *(pDouble+1)); //%d because you know it's an integer array
AfxMessageBox(szStr);

Of course, I assume that you know what reinterpret_cast does.

It is a crappy thing, but it's life -^ Carlo Pallini

Re: pointer casting

Jorge9-Apr-09 1:08

Jorge

9-Apr-09 1:08

Hi,
I am just trying to get a pointer to double from a pointer to int. That is what I mean by conversion. When you say 'manually' I actually dont know what you mean. I tried your code:

int nArray[] = {1, 2, 3, 4};
double* pDouble = reinterpret_cast<double*>(nArray);

but when I try to get *(pDouble(+i)) value(s) (for i=0,1,2,3) don´t get the expected 1.0,2.0,3.0,4.0

Re: pointer casting

Rajesh R Subramanian9-Apr-09 1:13

Rajesh R Subramanian

9-Apr-09 1:13

Have a closer look:

1. nArray is a an array of integers - the elements stored in the array are of 'int' data type.
2. You create a pointer variable, which actually is supposed to point to a double, but you made it (you wanted that) to point to the beginning address of the integer array.
3. Now, it's just that the pointer type is double, but is pointing to an int array. You still have not converted the individual int elements in the array to double type.
4. If that's what you want, you can try %g in place of %d in the CString::Format() statement and see the results. (this way, you are just 'interpreting' an integer as a double, and you haven't converted any of the array elements from one datatype to another)

But please remember that the elements in the array are *still* int ones and if you want every element of the array to be of double data type, you must do the conversion yourself for every element of the array. Changing a pointer won't do that, quite obviously.

Am I clear enough?

It is a crappy thing, but it's life -^ Carlo Pallini

Re: pointer casting

Jorge9-Apr-09 1:40

Jorge

9-Apr-09 1:40

Thank you very much.You both helped me to see my real problem.

Re: pointer casting

Divyang Mithaiwala9-Apr-09 1:01

Divyang Mithaiwala

9-Apr-09 1:01

Hi Jorge,

Why don't you use union?

For example you can take

union test
{
	int a[4];
	double c;
};

Do not trust a computer...
Always check what computer is doing

regards,
Divyang Mithaiwala
Software Engineer

Re: pointer casting

Jorge9-Apr-09 1:19

Jorge

9-Apr-09 1:19

Hi Divyang,
thanks so much. That solves the problem but, I can not believe there´s no straight way to do it.

Header file

p_19608-Apr-09 21:25

p_1960

8-Apr-09 21:25

Hi ,
When i include any header file in a cpp file May i know why the syntax is #include "test.h" why not #include <test.h> .Please let me know the difference...

Re: Header file

«_Superman_»8-Apr-09 21:29

«_Superman_»

8-Apr-09 21:29

<> will search in the include search path.
"" will also search the current directory in addition to the include search path.

«_Superman_»
I love work. It gives me something to do between weekends.

Re: Header file

CPallini8-Apr-09 21:31

CPallini

8-Apr-09 21:31

See [^]. BTW read posting guidelines [^].
Smile | :)

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.