Xform.cpp

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//-----------------------------------------------------------------------------
// Synopsis: Some support for XFORM transformations.
// Author: Copyright (c) Love Nystrom
// License: NNOSL (BSD descendant)
// Synopsis: This file contains definitions for common XFORM transformations.
//-----------------------------------------------------------------------------

#include <uLib/UtilFunc.h> // Decl in WinGDI section

//-----------------------------------------------------------------------------
// [x'y'1] = [x y 1] | eM11 eM12 0 |
//                   | eM21 eM22 0 |
//                   | eDx  eDy  1 |
//
// x' = x * eM11 + y * eM21 + eDx;
// y' = x * eM12 + y * eM22 + eDy;
//-----------------------------------------------------------------------------

// Translate: x' = x + dx ; y' = y + dy

XFORM* SetXformTranslate( XFORM* pxfm, float dx, float dy )
{
    static const XFORM xlate = {
        1,   0, // eM11  eM12
        0,   1, // eM21  eM22
        dx,  dy // eDx   eDy
        };
    *pxfm = xlate;
    return pxfm;
}

// Scale: x' = x * dx ; y' = y * dy

XFORM* SetXformScale( XFORM* pxfm, float dx, float dy )
{
    static const XFORM scale = {
        dx,  0,
        0,   dy,
        0,   0
        };
    *pxfm = scale;
    return pxfm;
}

// Rotate: x' = (x * cos A) - (y * sin A) ; y' = (x * sin A) + (y * cos A)

XFORM* SetXformRotate( XFORM* pxfm, double angle )
{
    float co = (float) cos( angle );
    float si = (float) sin( angle );
    static const XFORM rotate = {
        co,  si,
        -si, co,
        0,   0
        };
    *pxfm = rotate;
    return pxfm;
}

// Shear: x' = x + (Sx * y) ; y' = y + (Sy * x)

XFORM* SetXformShear( XFORM* pxfm, float sx, float sy )
{
    static const XFORM shear = {
        1,   sy,
        sx,  1,
        0,   0
        };
    *pxfm = shear;
    return pxfm;
}

// Reflect: x' = -x ; y' = -y

XFORM* SetXformReflect( XFORM* pxfm, bool rx, bool ry )
{
    float xf = float( rx ? -1 : 1 );
    float yf = float( ry ? -1 : 1 );
    static const XFORM reflect = {
        xf,  0,
        0,   yf,
        0,   0
        };
    *pxfm = reflect;
    return pxfm;
}

// EOF