C / C++ / MFC

Re: code for changing 32bits color bmp image into 8bits color bmp image

7-Nov-07 2:11

(1) i want to change a 32bits color bmp image into 8bits color bmp image,
anyone who has the source code?

(2)as to 24bits image, one pixel has 3 bytes, the 3 bytes respectively is the B ,G,R value, how about the 32bits iamge? from low byte to heigh byte , what is the value of the 4 bytes?

thanks
Smile | :)

C^hris L^osinger7-Nov-07 2:44

7-Nov-07 2:44

Lao Wang wrote:
what is the value of the 4 bytes?

RGBA. A = alpha = transparency

the only free RGBA to 8-bit code i'm aware of is part of one of the LibPNG utilities.

Re: code for changing 32bits color bmp image into 8bits color bmp image

King Tran7-Nov-07 3:44

Re: code for changing 32bits color bmp image into 8bits color bmp image

7-Nov-07 3:44

hey Chris Losinger, i only know the concept of alpha, but would you please give me the detail explain of it? why 32bits iamge has the alpha value?

as your reply, the sequence for the 4 bytes value of every pixel is R ,G, B, A, but i did an example, only the sequence is A, B , G ,R, the output image is well, what is the matter?

thanks ! Smile | :)

C^hris L^osinger7-Nov-07 4:01

7-Nov-07 4:01

Lao Wang wrote:
why 32bits iamge has the alpha value?

the alpha byte controls the transparency of that pixel - it allows the background to show through that one pixel.it's useful if you want to create images that can blend with their background, or that don't have straight edges.

Lao Wang wrote:
only the sequence is A, B , G ,R, the output image is well, what is the matter?

the actual order will depend on the application or API that creates or uses the image.

Re: code for changing 32bits color bmp image into 8bits color bmp image

King Tran8-Nov-07 3:51

Re: code for changing 32bits color bmp image into 8bits color bmp image

8-Nov-07 3:51

i have changed the Alpha byte for some values, but the image displayed has no change, when does the alpha byte value work? Big Grin | :-D

C^hris L^osinger10-Nov-07 7:15

10-Nov-07 7:15

how are you drawing it? many drawing APIs do not pay attention to alpha values.

Re: code for changing 32bits color bmp image into 8bits color bmp image

Mark Salsbery7-Nov-07 7:13

Mark Salsbery

7-Nov-07 7:13

Chris Losinger wrote:
RGBA.

It's not BGRA? Smile | :)

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: code for changing 32bits color bmp image into 8bits color bmp image

C^hris L^osinger7-Nov-07 7:42

7-Nov-07 7:42

only if you're talking about DIB/BMPs. the rest of the world gets the order right Poke tongue | ;-P

Re: code for changing 32bits color bmp image into 8bits color bmp image

Mark Salsbery7-Nov-07 7:46

Mark Salsbery

7-Nov-07 7:46

Heh. Well I don't get out in the rest of the world Poke tongue | ;-P

I was just joking about the vagueness though....the only clue I saw was
the OP stated "bmp" in the topic. Roll eyes | :rolleyes:

Cheers

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: code for changing 32bits color bmp image into 8bits color bmp image

Nishad S7-Nov-07 3:04

Nishad S

7-Nov-07 3:04

Have a look at http://www.codeproject.com/bitmap/Image_Bitdepth_Conversion.asp[^]

- NS -
[ODBaseBtn]

Re: code for changing 32bits color bmp image into 8bits color bmp image

King Tran7-Nov-07 3:44

7-Nov-07 3:44

thanks NS17!

A problem

minihotto7-Nov-07 1:50

minihotto

7-Nov-07 1:50

I create a windows form apllication, p2pport.
My form file name is Dlg.I get some errors.

error C2027: use of undefined type 'p2pport::CParams'
error C2227: left of '->setValue' must point to class/struct/union/generic type

in Dlg.cpp
params->setValue("Y", "123");

in my Dlg.h file

#include "params.h";<br />
namespace p2pport {<br />
<br />
	using namespace System;<br />
          ...............................<br />
<br />
	public ref class Dlg : public System::Windows::Forms::Form<br />
	{<br />
             CParams* params;<br />
        }<br />
}

in my param.h file

class CParams{<br />
      void setvalue(char* k, char* v);<br />
}

in my params.cpp
void CParams::setValue(char* k, char* v){ ..... return; }

Can anybody tell me what's wrong with it?
Appreciate your reply.
Jane

Nelek7-Nov-07 1:59

Nelek

7-Nov-07 1:59

Have you declared the pointer to your class before using it?

#include "MyClass.h"

MyClass* pMC;
pMC->DoSomething (...);

will work, but...

#include "MyClass.h"

pMC->DoSomething (...);

will give you the error you are posting

minihotto7-Nov-07 2:19

minihotto

7-Nov-07 2:19

THx for reply.
Is that means I can't declare it in Dlg.h?
I have to put "MyClass* pMC;" to Dlg.cpp?
Jane

Nelek7-Nov-07 2:55

Nelek

7-Nov-07 2:55

I dont say that you can not, I made it in header with member variables and in code with the local variables.

I have given you an example of that error code and the meaning. I don't think just putting the MyClass* pMC; in your Dlg.cpp will solve it. Although you can try it as well.

I think is more a question about the scope and how the relationships between classes are done. Your code is not recognising the other class, there is a point where the connections break.

Visual Studio 2005 SP2 & Debugging MFC DLL

toxcct7-Nov-07 1:59

toxcct

7-Nov-07 1:59

this is a Managed C++ question, so you should ask in the C++/CLI Forum[^]

thanks

[VisualCalc][Binary Guide][CommDialogs] | [Forums Guidelines]

Andy H7-Nov-07 0:53

Andy H

7-Nov-07 0:53

I have an MFC DLL project written in VS2003. I upgraded it to VS2005 SP2 and successfully build the DLL, despite setting the project options to use the projects .PDB I am unable to debug the DLL.

I was able to debug happily with VS2003 but CANNOT debug with VS2005! I have rolled back to VS2003 as until I can debug I will not be using VS2005.

Has anyone else had this problem with VS2005, and did you manage to debug a DLL?

KarstenK7-Nov-07 2:06

KarstenK

7-Nov-07 2:06

Check that your VS finds a dll with all the debug informations.
I debug VS2003 dlls with a VS2005 exe sometimes. Blush | :O

Greetings from Germany

Andy H7-Nov-07 3:13

Andy H

7-Nov-07 3:13

Yes, the projects .PDB file is output to the same folder in which my debug DLL is located as well as the EXE being run from which the DLL is called.

I can debug the VS2003 version of the DLL fine, just when I convert the DLL project to VS2005 and build in debug mode I cannot debug. I have even set the Debuggong | Symbols | location to the path to the <projectname>.pdb, but alas not able to hit my breakpoints!

I am sure there is a bug in VS2005 being unable to debug MFC DLL's!!! But would welcome anyone who has managed to debug an MFC DLL in VS2005.

Mark Salsbery7-Nov-07 7:18

Mark Salsbery

7-Nov-07 7:18

Andy H wrote:
I am sure there is a bug in VS2005 being unable to debug MFC DLL's!!!

Visual Studio will always have its problems, but that isn't one of them.

I would clean the solution and shut down VS. Then delete ALL intermediate files
including pdb, ilk - everything. Get rid of the Intellisense database as well.

Fire up VS and do a full rebuild. If it still won't work, you've got a project settings
issue somewhere.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]