A Fast Bresenham Type Algorithm For Drawing Ellipse - C / C++ / MFC Discussion Boards

al25003-Jul-07 19:31

3-Jul-07 19:31

Hi,

I know how to sort simple int or String based Carrays using qsort but I'd like to sort a CArray that is composed of a class with mixed variable types. Also, I'd like to sort the CArray based on one member of the base class and have the other members maintain their original association, ie.,

class CMyClass : public CObject
{
int m_A;
double m_B;
CString m_C;
}

CArray <cmyclass, cmyclass&=""> MyClassArray;

as an example say the members in MyClassArray are:

m_A, m_B, m_C
2 2.4 HI
1 5.6 BYE
4 8.3 NO

after sorting on the int field the sorted CArray would look like-

m_A, m_B, m_C
1 5.6 BYE
2 2.4 HI
4 8.3 NO

There is an articleon this site, "QuickSort enabled CArray template class" which describes sorting of user defined class members but it appears to sort the column selected independently without reordering the associated elements.

A very "inelegant" way of doing this would be to copy the sort field to a simple CArray, sort it and then locate the elements in the original array that correspond with the sorted elemnts and rebuild the complex array. I'm hoping there is better way.

Thanks

Re: Sorting a user class based CArray

Stephen Hewitt3-Jul-07 19:55

Stephen Hewitt

3-Jul-07 19:55

Try something like this. Note I use STL's collection classes and not MFC's.
----------------------------------

// Console.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>

class CMyClass
{
public:
CMyClass(int a, int b)
: m_A(a)
, m_B(b)
{}

int m_A;
double m_B;
};

// Function to sort by 'm_A'.
inline bool MyClassLessByA(const CMyClass &l, const CMyClass &r)
{
return l.m_A < r.m_A;
}

// Function to sort by 'm_B'.
inline bool MyClassLessByB(const CMyClass &l, const CMyClass &r)
{
return l.m_B < r.m_B;
}

// Function to write the class to an output stream.
inline std::ostream& operator<<(std::ostream &os, const CMyClass &cr)
{
os << "CMyClass(" << cr.m_A << ", " << cr.m_B << ")";
return os;
}

int main(int arvc, char* argv[])
{
using namespace std;

// Create an "array" and populate it.
vector<CMyClass> array;
array.push_back(CMyClass(1, 5.0));
array.push_back(CMyClass(2, 4.0));
array.push_back(CMyClass(3, 3.0));
array.push_back(CMyClass(4, 2.0));
array.push_back(CMyClass(5, 1.0));

// Shuffle the array into a random order.
random_shuffle(array.begin(), array.end());

// Output the shuffled array to the console.
cout << "Array before sorting:" << endl;
copy(array.begin(), array.end(), ostream_iterator<CMyClass>(cout, "\n"));
cout << endl;

// Sort by 'm_A'.
sort(array.begin(), array.end(), MyClassLessByA);

// Output the array to the console.
cout << "Sorted by 'm_A':" << endl;
copy(array.begin(), array.end(), ostream_iterator<CMyClass>(cout, "\n"));
cout << endl;

// Sort by 'm_B'.
sort(array.begin(), array.end(), MyClassLessByB);

// Output the array to the console.
cout << "Sorted by 'm_B':" << endl;
copy(array.begin(), array.end(), ostream_iterator<CMyClass>(cout, "\n"));
cout << endl;

return 0;
}

----------------------------------

The output on my system was the following:

Array before sorting:
CMyClass(5, 1)
CMyClass(4, 2)
CMyClass(1, 5)
CMyClass(3, 3)
CMyClass(2, 4)

Sorted by 'm_A':
CMyClass(1, 5)
CMyClass(2, 4)
CMyClass(3, 3)
CMyClass(4, 2)
CMyClass(5, 1)

Sorted by 'm_B':
CMyClass(5, 1)
CMyClass(4, 2)
CMyClass(3, 3)
CMyClass(2, 4)
CMyClass(1, 5)

Steve

My registered activex control is corrupted or missing.

adityarao313-Jul-07 18:35

adityarao31

3-Jul-07 18:35

My registered activex control seems to be corrupted or missing. Now before installing new one I want to remove it entirely even from VC++ registered activex control. How Can I remove it.
In similar manner how to remove added activex control in application.Because it gets added to standard controls list. How to remove it. I agree most of time when you add same control it gets overwritten but I dont want that, as I am not sure overwriting may not be correct.

|| Lust Causes Sorrow ||

RTTI option in compiler

vibindia3-Jul-07 17:30

vibindia

3-Jul-07 17:30

Hi
The typeid operator requires run-time type information (RTTI) to be generated, which must be explicitly specified at compile time through a compiler option.

Could i know,how to enable RTTI in VC6.0

VIBIN

"Fool's run away,where angle's fear to tread"

Re: RTTI option in compiler

User 5838523-Jul-07 17:36

User 583852

3-Jul-07 17:36

Its in the compiler option, under the Language category I think

Re: RTTI option in compiler

Rajkumar R3-Jul-07 18:22

Rajkumar R

3-Jul-07 18:22

project->settings->C/C++->Enable Run Time Type Information (RTTI)

Re: RTTI option in compiler

Stephen Hewitt3-Jul-07 18:24

Stephen Hewitt

3-Jul-07 18:24

1. Select "Project"->"Settings" from the application's menu.
2. Select the project and configuration.
3. Select the "C/C++" tab.
4. Select "C++ Language" in the "Category" combo.
5. Tick the "Enable Run-Time Type Information (RTTI)" check box.

Steve

A Fast Bresenham Type Algorithm For Drawing Ellipse

KienNT783-Jul-07 17:20

KienNT78

3-Jul-07 17:20

I read "A Fast Bresenham Type Algorithm For Drawing Ellipse" by John Kennedy Mathematics Department.
Below function was developed base on above algorithm.
I want to ask someone help me, how can develop below function to rotate ellipse.
If someone have an other ideals, can you help me!

<br />
void CBGraphics::DrawEllipse(HDC hDC, int x1, int y1, int x2, int y2, COLORREF color)<br />
{<br />
        long x, y, XChange, YChange, EllipseError, TwoASquare, TwoBSquare, StoppingX, StoppingY;	<br />
	TwoASquare = 2 * x2 * x2;<br />
	TwoBSquare = 2 * y2 * y2;<br />
	x = x2;<br />
	y = 0;<br />
	XChange = y2 * y2 * (1 - 2 * x2);<br />
	YChange = x2 * x2;<br />
	EllipseError = 0;<br />
	StoppingX = TwoBSquare * x2;<br />
	StoppingY = 0;<br />
	while( StoppingX >= StoppingY)<br />
	{<br />
		Put4Pixel(hDC, x1, y1, x, y, color);<br />
		y++;<br />
		StoppingY += TwoASquare;<br />
		EllipseError += YChange;<br />
		YChange += TwoASquare;<br />
		if( ( 2 * EllipseError + XChange) > 0 )<br />
		{<br />
			x--;<br />
			StoppingX -= TwoBSquare;<br />
			EllipseError += XChange;<br />
			XChange += TwoBSquare;<br />
		}<br />
	}<br />
	x = 0;<br />
	y = y2;<br />
	XChange = y2 * y2;<br />
	YChange = x2 * x2 * (1 - 2 * y2);<br />
	EllipseError = 0;<br />
	StoppingX = 0;<br />
	StoppingY = TwoASquare * y2;<br />
	while (StoppingX <= StoppingY)<br />
	{<br />
		Put4Pixel(hDC, x1, y1, x, y, color);<br />
		x++;<br />
		StoppingX += TwoBSquare;<br />
		EllipseError += XChange;<br />
		XChange += TwoBSquare;<br />
		if( (2 * EllipseError + YChange) > 0)<br />
		{<br />
			y--;<br />
			StoppingY -= TwoASquare;<br />
			EllipseError += YChange;<br />
			YChange += TwoASquare;<br />
		}<br />
	}<br />
}<br />

Re: A Fast Bresenham Type Algorithm For Drawing Ellipse

Rajkumar R3-Jul-07 19:22

Rajkumar R

3-Jul-07 19:22

Hi,
This Algorithm is based on 4 point symmetry of ellipse. And when the ellipse is rotated this symmetry will lost at numerous position. This algorithm can be used to increase the speed of plotting ellipse in a raster system for ellipse in its symmetric shape.
The parameters to the function is center and X and Y radius. I strongly think this algorithm cannot be used for plotting ellipse in all ellipse transformation.

Re: A Fast Bresenham Type Algorithm For Drawing Ellipse [modified]

KienNT783-Jul-07 20:53

KienNT78

3-Jul-07 20:53

Thanks you for your advice. by the way, Can you give me an other algorithm that you think it's suit to solve my trouble? Wink | ;)

monitoring user connections in my PC

m-a-s-a-k-i-t-o-n3-Jul-07 15:35

m-a-s-a-k-i-t-o-n

3-Jul-07 15:35

Hi,

i'm making a program that monitors user connection and what that user is doing in my PC. Please let me know how to do this. I'm currently on a LAN connection. I just want to monitor computers are connecting to my PC.;);)

I know this is kindof a general question but i just do not know where to start.

Thanks.

Re: monitoring user connections in my PC

David Crow3-Jul-07 18:10

David Crow

3-Jul-07 18:10

How about NetConnectionEnum() and NetFileEnum()?

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: monitoring user connections in my PC

m-a-s-a-k-i-t-o-n3-Jul-07 22:16

m-a-s-a-k-i-t-o-n

3-Jul-07 22:16

Thanks David,

I assume this is only applicable if I'm sharing a resource on my PC. I would also want to monitor those computers that connect on my PC even if I'm not sharing..and, by the way, not only from LAN but also from those that connect to my PC through the internet.

Thank you!

Custom Vector Allocator

miketra3-Jul-07 10:04

miketra

3-Jul-07 10:04

Is it possible to create a custom vector allocator that allows you to allocate the maximum amount of memory your vector will ever need during vector instantiation, thereby allowing you to avoid dynamic allocation/reallocation/deallocation during program execution? When you add an item to your vector, it uses the available memory. When you remove an item from your vector, it will not delete the memory, it will only clear it and allow it to be re-used.

If this is possible, can someone provide guidance on how to code this, or provide a link where something like this is accomplished or talked about? I have no experience with Allocators, so I apologize if this is a dumb question.

I need to create a sorted list that provides array indexing capability, but also avoids dynamic allocation and deallocation.

Re: Custom Vector Allocator

Maximilien3-Jul-07 10:31

Maximilien

3-Jul-07 10:31

you could use std::vector::reserve to allocate the number of element.

Maximilien Lincourt
Your Head A Splode - Strong Bad

Vector Function erase()

miketra3-Jul-07 10:55

miketra

3-Jul-07 10:55

Thanks for the info.

Let's say I use reserve, and I reserve memory for 5 integers, 1 through 5.
If I call erase() on integer 3, how will this affect the internal memory structure of the vector? Will the vector have an empty space where 3 used to be (e.g. 1,2,-,4,5) or will the remaining elements in the vector get "pushed" over (e.g. 1,2,4,5)?

Re: Vector Function erase()

Stephen Hewitt3-Jul-07 13:59

Stephen Hewitt

3-Jul-07 13:59

If you erase an element from a vector the elements after the deleted element are moved to fill the space. A vector's memory never gets smaller unless you use the following trick:

vector<int> copy(source);
source.swap(copy);

Steve

How to prevent CMainFrame from restores????

SandipG 3-Jul-07 9:22

SandipG

3-Jul-07 9:22

I tried ~WS_THICK_FRAME in precreate window.
Maximize box is disabled but when i double click on title bar it always restores
how to prevent this???
Problem is solved......
I solved using WM_NCLBUTTONDBLCLK any other solution.

Re: How to prevent CMainFrame from restores????

MANISH RASTOGI3-Jul-07 18:46

MANISH RASTOGI

3-Jul-07 18:46

Override OnNcLButtonDblClk().

Manish Rastogi

runtime type casting

wallbrick3-Jul-07 6:00

wallbrick

3-Jul-07 6:00

I'm new to c++ and this forum, so please...

I want to convert one type(int/float/double, can be 8/16/32/64bits), which is unknow when compiling, to another type, which is also unknow at compile time, in some function. One way is to use a vitual function and override that function with different arugment types. It's a heavy function with a lot of coding, so I want to search some other options.
I'm wondering if there is a solution so that I only need to write one conversion function which can take care of whatever input/output types.

Here are some pseudo codes which I'm not sure if they can be somehow realized. Hope it wouldn't confuse you.

define type T*;

Convert( T* in, T* out)
{
for_each_datum_in
{ *in=(type of out)*out;
}
}

//call the function here
Convert( TypeOfIn * in, TypeOfOut * out);

now here am i

Re: runtime type casting

Matthew Faithfull3-Jul-07 6:18

Matthew Faithfull

3-Jul-07 6:18

Strictly speaking you can't do what you've asked about in ordinary C++. Only using .NET reflection, but the chances are that the set of types is not really 'unknown' at compile time it's just that you don't want to have to write much or any new code when you change that set?
If that's true you have a chance. Consider using templates e.g.

<br />
template< typename Ti, typename To ><br />
Convert( Ti* pIn, To* pOut )<br />
{<br />
//Conversion code would go here but it's going to have to make<br />
//some assumptions about the types in order to work<br />
//which means it won't work with just anything :(<br />
}<br />

In the end you'll probably have to provide lots of type specific template overrides like

<br />
Convert( double* pIn, char* pOut )<br />
{<br />
//a call to printf may occur somewhere in here :omg:<br />
}<br />

which is not much better than where you started out.
If you've hit this problem and most of us have D'Oh! | :doh:

then you probably need to go back and look at your design with a 'what is this really try to achieve' hat on Smile | :)

Nothing is exactly what it seems but everything with seems can be unpicked.

Re: runtime type casting

led mike3-Jul-07 6:22

led mike

3-Jul-07 6:22

Is there some reason a template function won't work?

Re: runtime type casting

Nuxser3-Jul-07 15:59

Nuxser

3-Jul-07 15:59

Must admit that I am not sure if I understood your problem. But according to I interpreted,

when you talk about converting types, you imply the concept of "casting" (Casting one data type to be another). With respect to your given pseudocode, I guess you want the type pointed by "out" to be treated as type "in" so that the assignment can work nicely. Thus you want to cast the type pointed by "out" to be as type pointed by "in".

If that understanding is true ...

You need to delve in to understanding how "type casting" works in C++. A nice tutorial -

http://www.cplusplus.com/doc/tutorial/typecasting.html

I like it as they quickly goes into how type casting with classes/structs and pointer to those needs to be carefull than for basic types.

Also for completeness, even in the case of template, it will eventually boils down to type casting as soon as the type is provided for the templates. So if you have defined two template types being them as type independent, during the runtime they are associated with provided types, hence the game boils down to type conversion between those two types.

So understanding the "type casting" will enlighten you about how to do it and if done will it be meaning full.

And for the conclusion, you will see that even though it is not a runtime error some casting will not be meaningfull or result in an wanted manner. There is no such freedom as converting ANY type to ANY type. Its not meaningfully possible (such as converting a student info class to a integer number).

Hope it can help.

Regards

Re: runtime type casting

Nuxser3-Jul-07 16:17

Nuxser

3-Jul-07 16:17

Just in case I wan't clear about it - I agree with Matthew Faithfull.

And interestingly enough, quick Googling shows that there seems to be few implementation of Reflection in C++.

http://www.extreme.indiana.edu/reflcpp/

Hey, Its C++, It can do everything ... Wink | ;)

get Distinguished Email id from GAL

Ganesh_T3-Jul-07 5:47

Ganesh_T

3-Jul-07 5:47

I am developing an app which will fetch addresses from the GAL. I need the email address of the users. I get those in the exchnage format (Electronic mail format)

for eg. /c=US/a=att/p=Microsoft/o=Finance/ou=Purchasing/s=Furthur/g=Joe

and need those in

I am using Exchange SDk to fetch the contacts from GAL.

for e.g : xyz@fgh.com

"A winner is not one who never fails...but the one who never quits"

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