pressure.cpp

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// $Id: pressure.cpp 1282 2006-06-09 09:46:49Z alex $
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 */
// Pressure - functions for smoothing freehand pressure data

#include "camtypes.h"
#include "pressure.h"

//#include "paths.h" - in camtypes.h [AUTOMATICALLY REMOVED]
#include "pathtrap.h"
#include "valfunc.h"

DECLARE_SOURCE("$Revision: 1282 $");

CC_IMPLEMENT_MEMDUMP(PressureSmoother, CC_CLASS_MEMDUMP)


#define new CAM_DEBUG_NEW


/********************************************************************************************

>   PressureSmoother::PressureSmoother()

    Author;     Jason
    Created:    30/1/97
    Purpose:    Constructor

********************************************************************************************/

PressureSmoother::PressureSmoother()
{
}



/********************************************************************************************

>   PressureSmoother::~PressureSmoother()

    Author;     Jason
    Created:    30/1/97
    Purpose:    Destructor

********************************************************************************************/

PressureSmoother::~PressureSmoother()
{
}



/********************************************************************************************

>   ValueFunction *PressureSmoother::Smooth(Path *pSourceData, INT32 LineWidth)

    Author:     Jason_Williams (Xara Group Ltd) <camelotdev@xara.com>
    Created:    21/1/97
    Inputs:     pSourceData - The path containing the pressure data to smooth.
                              The pressure information should be held in the Width channel
                              in the ExtraInfo of the path

                LineWidth   - The maximum "radius" of the line (half the line width) which
                              will be used when stroking this path.

    Returns:    NULL if it failed (no error is set), else
                a pointer to a new ValueFunction object which represents the pressure
                information form this path. The caller is responsible for deleting this
                new object when they're finished with it.

    Purpose:    Reads raw recorded pressure information from a path and smooths it,
                creating a new ValueFunction object representing the pressure function.

    Notes:      Smoothing works as follows:
                1) Create a graph of the pressure samples, with pressure (y) versus
                   position along the path (x). Store this graph in a Path.

                2) Smooth the straight line segments in this graph into curve segments
                   At present, this is done by replacing everything between 2 local
                   minima/maxima by an S-shaped curve. This interpolation can be done by
                   a ValueFunctionPressureS object in real-time, so we create one of them.

********************************************************************************************/

ValueFunction *PressureSmoother::Smooth(Path *pSourceData, INT32 LineWidth)
{
    ERROR3IF(pSourceData == NULL, "Illegal NULL param");

    // Find the recorded pressure values (if any)
    PathWidth *pWidthArray = pSourceData->GetWidthArray();
    if (pWidthArray == NULL)
        return(NULL);

    const INT32 NumCoords   = pSourceData->GetNumCoords();
    DocCoord *pCoords   = pSourceData->GetCoordArray();

    if (NumCoords < 2)
        return(NULL);

    // Create a ValueFunction to return. We use an "S" curve interpolated pressure function
    ValueFunctionPressure *pValFunc = new ValueFunctionPressureS;
    if (pValFunc == NULL)
        return(NULL);

    // Calculate the maximum pressure value recorded. This should be EXTRAVALUEMAX
    // but sometimes we seem to get bigger values.
    INT32 MaxPressure = pWidthArray[0];
    for (INT32 i = 1; i < NumCoords; i++)
    {
        if (pCoords[i].y > MaxPressure)
            MaxPressure = pWidthArray[i];
    }

    // If this pressure was smaller than EXTRAVALUEMAX, then we use that as the maximum,
    // because we don't want to scale thin strokes up to max width!
    if (MaxPressure < (INT32)EXTRAVALUEMAX)
        MaxPressure = EXTRAVALUEMAX;

    float Position      = 0.0f;
    float LastPosition  = Position;
    INT32 Diff          = 0;
    INT32 LastDiff      = pWidthArray[1] - pWidthArray[0];

    pValFunc->AddPressure(Position, (float)pWidthArray[0] / (float)MaxPressure);

    // --- Now loop through the pressure samples, scaling them into the correct range, calculating
    // proper "position" values for them, and smoothing the data (by replacing all points between
    // minima and maxima with s-shaped interpolated segments)
    for (INT32 Index = 1; Index < NumCoords - 1; Index++)
    {
        // Record the pressure sample. We chuck away all samples between minima/maxima
        // as we go, and also wheedle out any zero-length sections that might crop up.
        // Then the ValueFunction will interpolate between the values as it sees fit (with S-shaped curves)
        if (Position > LastPosition)
        {
            LastPosition = Position;

            Diff = pWidthArray[Index] - pWidthArray[Index - 1];
            if ((Diff > 0 && LastDiff <= 0) || (Diff < 0 && LastDiff >= 0))
            {
                // We have found a min/maximum. Record this point.
                pValFunc->AddPressure(Position, (float)pWidthArray[Index] / (float)MaxPressure);
                LastDiff = Diff;
            }
        }

        // Work out approximate "travel" along the path so each width sample has a known position
        // [This should be calculated in the same way as in TrapEdgeList::ProcessEdgePositions, pathtrap.cpp]

#if TRUE
        // This now simply calculates distance down the centreline.
        // Much faster & simpler, and it turns out it gives better results after all!
        const double dx = (double) (pCoords[Index-1].x - pCoords[Index].x);
        const double dy = (double) (pCoords[Index-1].y - pCoords[Index].y);
        Position += (float) sqrt((dx * dx) + (dy * dy));
#else
    /*
        // Calculate the line normals to the left and right of the point
        NormCoord Normal1;
        NormCoord Normal2;
        Normal1.SetNormalToLine(pCoords[Index],     pCoords[Index - 1]);
        Normal2.SetNormalToLine(pCoords[Index + 1], pCoords[Index]);

        // Calculate the "left" parallel edge
        DocCoord P1(    pCoords[Index-1].x + (INT32)((double) LineWidth * Normal1.x),
                        pCoords[Index-1].y + (INT32)((double) LineWidth * Normal1.y));
        DocCoord P2(    pCoords[Index  ].x + (INT32)((double) LineWidth * Normal2.x),
                        pCoords[Index  ].y + (INT32)((double) LineWidth * Normal2.y));
        double dx = P1.x - P2.x;
        double dy = P1.y - P2.y;
        double LeftTravel = sqrt((dx * dx) + (dy * dy));

        // Calculate the "right" parallel edge
        P1 = DocCoord(  pCoords[Index-1].x - (INT32)((double) LineWidth * Normal1.x),
                        pCoords[Index-1].y - (INT32)((double) LineWidth * Normal1.y));
        P2 = DocCoord(  pCoords[Index  ].x - (INT32)((double) LineWidth * Normal2.x),
                        pCoords[Index  ].y - (INT32)((double) LineWidth * Normal2.y));
        dx = P1.x - P2.x;
        dy = P1.y - P2.y;
        double RightTravel = sqrt((dx * dx) + (dy * dy));

        // And increment Position by the larger of the 2 travel distances
        Position += (float)( (LeftTravel > RightTravel) ? LeftTravel : RightTravel );
*/
#endif
    }

    // And always add a knot at the very end of the curve
    pValFunc->AddPressure(Position, (float)pWidthArray[NumCoords - 1] / (float)MaxPressure);

    pValFunc->NormalisePositions();     // And normalise all positions to lie between 0.0 and 1.0

    return(pValFunc);
}

---