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Round Buttons

, 11 Jun 2003
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A class that turns rectangular buttons into round buttons.

Sample Image

Introduction

I wanted a button that looked exactly like normal buttons, but instead I wanted them circular. This class can be used like any other owner drawn control - simply include the header file, and declare your button controls as CRoundButton instead of CButton

First of all I make sure the buttons are circles (and not ellipses) and store the centre and radius of the button. Next I simply make the button owner drawn and draw it like every other owner drwn button, but instead of being able to use nice routines like Draw3dRect, I had to roll my own circle drawing routine which would draw each pixel with the correct colour dependant on the point on the circle I was drawing.

I will not include the full source in this page - it is available for download here. The owner draw part is simple and follows along the lines of any other owner drawn button. The circle drawing routine is a standard algorithm, with the only modification in calculating the pixel colour. Given two colours crBright and crDark, and an angle relative to the x-axis, the colour for a pixel can be calculated using the following.

COLORREF GetColour(double dAngle, COLORREF crBright, COLORREF crDark)
{
#define Rad2Deg            180.0/3.1415 
#define LIGHT_SOURCE_ANGLE  -2.356    // -2.356 radians = -135 degrees, 
                                      // i.e. From the top left of the screen

    ASSERT(dAngle > -3.1416 && dAngle < 3.1416);
    double dAngleDifference = LIGHT_SOURCE_ANGLE - dAngle;

    if (dAngleDifference < -3.1415) 
        dAngleDifference = 6.293 + dAngleDifference;
    else if (dAngleDifference > 3.1415) 
        dAngleDifference = 6.293 - dAngleDifference;

    double Weight = 0.5*(cos(dAngleDifference)+1.0);

    BYTE Red   = (BYTE) (Weight*GetRValue(crBright) + 
                        (1.0-Weight)*GetRValue(crDark));
    BYTE Green = (BYTE) (Weight*GetGValue(crBright) + 
                        (1.0-Weight)*GetGValue(crDark));
    BYTE Blue  = (BYTE) (Weight*GetBValue(crBright) + 
                        (1.0-Weight)*GetBValue(crDark));

    return RGB(Red, Green, Blue);
}

This is a simple linear interpolation between the two colours based on the cosine of the angle between the light source and the point. Angles are measured from the +ve x-axis (i.e. (1,0) = 0 degrees, (0,1) = 90 degrees ), but remember: positive y points down!

Update

Tom Kalmijn kindly added routines that post-process the button image to smooth out the jagged edges. His method uses a nearest-neighbours algorithm to interpolate missing pixels. It's not particularly fast but it does increase smoothing.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Chris Maunder
Founder CodeProject
Canada Canada
Chris is the Co-founder, Administrator, Architect, Chief Editor and Shameless Hack who wrote and runs The Code Project. He's been programming since 1988 while pretending to be, in various guises, an astrophysicist, mathematician, physicist, hydrologist, geomorphologist, defence intelligence researcher and then, when all that got a bit rough on the nerves, a web developer. He is a Microsoft Visual C++ MVP both globally and for Canada locally.
 
His programming experience includes C/C++, C#, SQL, MFC, ASP, ASP.NET, and far, far too much FORTRAN. He has worked on PocketPCs, AIX mainframes, Sun workstations, and a CRAY YMP C90 behemoth but finds notebooks take up less desk space.
 
He dodges, he weaves, and he never gets enough sleep. He is kind to small animals.
 
Chris was born and bred in Australia but splits his time between Toronto and Melbourne, depending on the weather. For relaxation he is into road cycling, snowboarding, rock climbing, and storm chasing.
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Comments and Discussions

 
GeneralExcellent article! PinmemberDrABELL16-Sep-09 12:39 
GeneralA nice article PinmemberDerek Bartram22-Mar-08 10:53 
Questionhow to implement this class to see the buttons Pinmembertoutounesan_bg14-Aug-07 11:12 
QuestionHow to add button dynamic in VB6.0? Pinmembermyphuong2442-Sep-05 19:32 
GeneralSome explanations,please... PinmemberDudi Avramov12-Dec-04 4:49 
GeneralRe: Some explanations,please... PinmemberDudi Avramov13-Dec-04 0:14 
QuestionCan anyone show me some good ebook about design control Pinmemberhoangbao6-Nov-04 2:58 
QuestionHow to insert this in view class Pinmembermymauve2119-Mar-04 1:10 
I tried to draw this button in my project directly inserting it in the view but it gives assertion error .

commenting the following line obviously removes this error but the button drawn is not circular one infact it draws only a grey rectangle.
 
ASSERT(dAngle > -3.1416 && dAngle < 3.1416);
 
What am i missing ???
 

AnswerRe: How to insert this in view class Pinmembermaruku8-Nov-04 18:58 
AnswerRe: How to insert this in view class Pinmembertoucherzxb25-Nov-07 20:09 
QuestionUnderline the shortcut character? PinmemberAAntix7-Nov-03 10:15 
Questionhow to create command button through code PinsussAnonymous30-Sep-03 4:30 
QuestionHow To Create a Round Shape Control ? PinmemberVikrant Vikrant29-Jun-03 21:58 
GeneralNot the most important thing in the world Pinmembertkalmijn9-Jun-03 21:48 
GeneralRe: Not the most important thing in the world PinadminChris Maunder10-Jun-03 4:57 
GeneralWhere can we declare Pinmemberaimenkawaz5-Oct-02 11:53 
GeneralRound Button Java PinmemberEric Minor26-Jun-02 5:38 
GeneralRe: Round Button Java PinsussSebuliba Peter1-Jan-03 19:48 
Question#How to implement a round button in C#? PinmemberAnonymous24-Jun-02 6:42 
GeneralKewl... PinmemberHockeyDude2-Apr-02 14:35 
GeneralRGN qustion Pinmemberkuzi6-Mar-02 5:53 
GeneralThe size of the circle PinmemberHuda2-Sep-01 4:34 
GeneralCool but... PinmemberEarl Rex Arao-arao10-May-01 23:11 
QuestionHow to add a bitmap to the round buttons? PinsussBernd Giesen8-Jun-00 22:52 
Questionreal round button ?!? Pinsusstuvok18-Mar-00 20:55 

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