xform_2d.cpp

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/*
 * xform_2d.cpp
 *
 * Copyright (C) 2007   Thomas A. Vaughan
 * All rights reserved.
 *
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the <organization> nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THOMAS A. VAUGHAN ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THOMAS A. VAUGHAN BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * Implementation of transforms.
 */

// includes --------------------------------------------------------------------
#include "xform_2d.h"           // always include our own header first!

#include "perf/perf.h"


void
xform_2d_t::transformRect
(
IN const rect_t& in,
OUT rect_t& out
)
const throw() 
{
        // this routine is so fast the timer impacts the performance!
        // only enable timer for debugging
        // perf::Timer timer("xform_2d_t::transformRect");

        // DPRINTF("in transformRect()");

        point_t p[4];
        p[0].x = in.left;       p[0].y = in.top;
        p[1].x = in.left;       p[1].y = in.bottom;
        p[2].x = in.right;      p[2].y = in.top;
        p[3].x = in.right;      p[3].y = in.bottom;

        point_t q;
        this->transformPoint(p[0], q);
        out.left = out.right = q.x;
        out.top = out.bottom = q.y;

        for (int i = 0; i < 4; ++i) {
                this->transformPoint(p[i], q);
                // DPRINTF("  (%5.2f, %5.2f) --> (%5.2f, %5.2f)",
                //     p[i].x, p[i].y, q.x, q.y);

                if (q.x < out.left)
                        out.left = q.x;
                if (q.x > out.right)
                        out.right = q.x;
                if (q.y < out.top)
                        out.top = q.y;
                if (q.y > out.bottom)
                        out.bottom = q.y;
        }
}



////////////////////////////////////////////////////////////////////////////////
//
//      Matrix inversion
//
//      See my 3 March 2007 journal entry.
//
//      Basically,          |  R   d  |
//                      T = |  0   1  |
//
//      Where R is a 2x2 matrix (rotation and scaling), and d is a 2d column
//      vector (x,y displacement).  The inverse of T = inv(T) =
//
//               |  inv(R)     -inv(R) d  |
//      inv(T) = |    0             1     |
//
//                                   |  1   0   0  |
//      so T * inv(T) = inv(T) * T = |  0   1   0  |
//                                   |  0   0   1  |
//
////////////////////////////////////////////////////////////////////////////////
void
xform_2d_t::setToInverseOf
(
IN const xform_2d_t& T
)
throw()
{
        // get the determinant
        float det = T.t00 * T.t11 - T.t01 * T.t10;
        ASSERT(det, "Taking the inverse of a matrix with null determinant");
        float inv_det = 1.0 / det;

        // the rotation part is a straightforward inverse (see above)
        t00 = inv_det * T.t11;
        t11 = inv_det * T.t00;
        t01 = -inv_det * T.t01;
        t10 = -inv_det * T.t10;

        // inverse displacement (see above)
        dx = -inv_det * (T.t11 * T.dx - T.t01 * T.dy);
        dy = -inv_det * (T.t00 * T.dy - T.t10 * T.dx);
}