RE: Drawing and filling in shapes

[Tang, Diana]

Thanks alot.  This is great.  

________________________________

From: %%email.bounce%% on behalf of Luc Le Blanc
Sent: Mon 17/09/2007 4:36 PM
To: Palm Developer Forum
Subject: RE: Drawing and filling in shapes



Tang, Diana wrote:

> Thanks.  Do you know anything about filling in and drawing
> triangle shapes? 

Note: DrawLine() is a wrapper to either call WinDrawLine (regular PalmOS API) 
or HRWinDrawLine (Sony hi res API).


// *** WinFillTriangle ***
// Adapted from Tom Z. Meinlschmidt's code ([EMAIL PROTECTED])
// -> points : pointer to array of 3 PointType structs (Int16 x, y)

void WinFillTriangle( PointType *points )
{
    PointType          *top = NULL;
    PointType          *down = NULL;
    PointType          *middle = NULL;
    float               xStart, xEnd, dTopDown, dTopMiddle, dMiddleDown;
    Int16               i, y;


    for ( i = 3; i--; )
    {
        if ( ( top == NULL ) || ( top->y > points[ i ].y ) )
            top = &points[ i ];

        if ( ( down == NULL ) || ( down->y < points[ i ].y ) )
            down = &points[ i ];
    }

    for ( i = 3; i--; )
    {
        if ( ( top == &points[ i ] ) || ( down == &points[ i ] ) )
            continue;

        middle = &points[i];
        break;
    }

    dTopDown =    ( y = ( down->y   - top->y    ) ) == 0 ? 1.0 : ( float ) ( 
down->x   - top->x )    / ( float ) y;         // compute slopes
    dTopMiddle =  ( y = ( middle->y - top->y    ) ) == 0 ? 1.0 : ( float ) ( 
middle->x - top->x )    / ( float ) y;         // but set slope = 1.0 if
    dMiddleDown = ( y = ( down->y   - middle->y ) ) == 0 ? 1.0 : ( float ) ( 
down->x   - middle->x ) / ( float ) y;         // divisor is 0

    for ( i = top->y; i <= down->y; i++ )
    {
        y = i - top->y;
        xStart = top->x + ( dTopDown * y );

        if ( i < middle->y )
            xEnd = top->x + ( dTopMiddle * y );
        else
            xEnd = middle->x + ( dMiddleDown * ( i - middle->y ) );

        DrawLine( ( Int16 ) xStart, i, ( Int16 ) xEnd, i );                     
                            // draw horizontal lines starting
    }                                                                           
                            // from top of triangle
}


--
Luc Le Blanc





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