C / C++ / MFC

Re: code to analyze bitmap then create predefined palette of colors in bitmap?

24-Jan-09 5:01

Richard Perrine wrote:
example code that analyzes the colors in a bitmap

Define 'analyze'. To just gather colours, I'd probably go through the bitmap a pixel at a time and store the RGB triplet for each pixel into a std::set. That would make it easy enough to get a list of the unique colours in the bitmap.

To cull the colours to a smaller number (as required if you want to define a fixed palette for the image), you'd use some form of colour quantisation[^].

Richard Perrine wrote:
code that organizes the colors sampled into a palette of 16x16 or 32x32

Maybe you can get some ideas from this color picker control[^]? The source is available.

Richard Perrine24-Jan-09 5:14

Richard Perrine

24-Jan-09 5:14

Thank you, Stuart.

Re: code to analyze bitmap then create predefined palette of colors in bitmap?

Randor 24-Jan-09 6:59

Randor

24-Jan-09 6:59

Richard Perrine wrote:
can anyone help?

These are some excellent color quantization links that you may be interested in.

Floyd-Steinberg implemented in C[^]

Octree Color Quantization[^]

Best Wishes,
-David Delaune

explorer in Windows CE

Miss_F24-Jan-09 2:18

Miss_F

24-Jan-09 2:18

Hi,
I want to use an explorer in my program (it's a C++ program) which is under Windows CE platform. I want to know that is it applicable or not? If yes, does any body know how can I do it?
(If here is not a right forum, Sorry, I don't know under which topic I should write my question)
Thanks a lot
Sincerely Yours
Miss_F

Stuart Dootson24-Jan-09 3:09

24-Jan-09 3:09

Miss_F wrote:
an explorer

What do you mean by 'an explorer'? If you mean manipulating the filesystem/namespace using explorer interfaces like IFolderView[^], then I suspect you're out of luck. If you mean a treeview, then you should be OK[^].

Miss_F24-Jan-09 3:15

Miss_F

24-Jan-09 3:15

I mean adding Internet browsing (using browser) functionality to my application.

Stuart Dootson24-Jan-09 4:43

24-Jan-09 4:43

Looks like you can[^]?

Get TrackBar Value in Form from a Thread

Miss_F24-Jan-09 18:53

Miss_F

24-Jan-09 18:53

Thanks for your help

Member 391913824-Jan-09 1:16

Member 3919138

24-Jan-09 1:16

A trackBar->Value in a form has to be read out from a thread. I read so many articles, but still I got a problem.

I use a delegate which should return me the value of the trackBar position:
delegate int DelegateTrackBarCallBack(System::Object ^object);

I started the Thread by a ParametriziedThreadStart after a Button-Click

Thread^ oThread = gcnew Thread(gcnew ParameterizedThreadStart(&ProcessCANMessage::CAN_Thread::CANThread));

In CANThread I do

target_velocity=Get_TrackBar1_Value(object);

with

int ProcessCANMessage::CAN_Thread::Get_TrackBar1_Value(System::Object^ object)
{
   CAN_Anbindung::Form1^ form;
   form = (CAN_Anbindung::Form1^)object;
   int trackBar_Value;
   if (form->trackBar1->InvokeRequired==false)
   {
	   trackBar_Value=form->trackBar1->Value;
   }
   else
   {
	   CAN_Anbindung::Form1::DelegateTrackBarCallBack ^d = gcnew CAN_Anbindung::Form1::DelegateTrackBarCallBack(Get_TrackBar1_Value);
	   form->Invoke(d, gcnew array<system::object^>{form});
   }
   return (trackBar_Value);
}

During debugging the correct value is assigned to trackBar_Value. But when leaving Get_TrackBar1_Value trackBar_Value is set to "0".

Any ideas what to do?

Stuart Dootson24-Jan-09 1:37

24-Jan-09 1:37

Member 3919138 wrote:
Any ideas what to do?

Post to the C++/CLI[^] forum, as that's what you're using?

From what I can understand of your message, you're expecting trackBar_Value to keep its value in two different invocations of Get_TrackBar1_Value? Nope - local variables don't do that unless they're static. However - doesn't Invoke return the return value of the delegate? So you could do something like this?

trackBar_Value = form->Invoke(d, gcnew array<system::object^>{form});

You might need some casting to convert Invoke's return value from System::Object to int - wouldn't know - I've never really used .NET, never mind C++/CLI.

Member 391913824-Jan-09 1:56

Member 3919138

24-Jan-09 1:56

I tried this befor
I got an error
1>.\ProcessCANMessage.cpp(74) : error C2440: '=': 'System::Object ^' kann nicht in 'int' konvertiert werden

Stuart Dootson24-Jan-09 2:19

24-Jan-09 2:19

Did you convert as shown in this article[^]?

int z = 44;
Object^ o = z; //implicit boxing
int y = *reinterpret_cast<int^>(o); //unboxing

Chris.G.Weber24-Jan-09 6:40

Chris.G.Weber

24-Jan-09 6:40

I will try that. Thanks for your answers and help!

I used a code which shown in one of the articles from this forum which helps to control 4 Progressbars in a Form from 4 Threads.

See: http://www.codeproject.com/KB/mcpp/managedsafethreads.aspx[^]
It works fine, since the delegate function seems to be recalled until the InvokeRequired-property is false. in this case the progressbars can be controlled directly in the thread by "form->progressBar1->PerformStep();"
In my case I want to get the Value (Position) of the trackBar-component. So if the delegate function is called 2 times we have a recursive calling of the same function. I assumed that the return value is then overwritten by the previous call of my function "Get_TrackBar1_Value(object)".

I will let you know about the result.