matrix.c.svn-base

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#include "matrix.h"
long getX( matrix,x,  y)
Matrix *matrix;
long x;
long y;

{ //printf("ScaleX is %f  RotateSkew0 is %f translatex is %ld\n",matrix->ScaleX,matrix->RotateSkew0,matrix->TranslateX);
    return (long) (x*matrix->ScaleX+y*matrix->RotateSkew0+matrix->TranslateX);
}


long getY( matrix,x,  y)
Matrix *matrix;
long x;
long y;
{//        printf("RotateSkew1 is %f  ScaleY is %f matrix->TranslateY is %ld\n",matrix->RotateSkew1,matrix->ScaleY,matrix->TranslateY);
    return (long) (x*matrix->RotateSkew1+y*matrix->ScaleY+matrix->TranslateY);
}




void MatrixPrepare(matrix)
Matrix *matrix;
{
    matrix->ScaleX = 1.0;
    matrix->ScaleY = 1.0;
    matrix->RotateSkew0 = matrix->RotateSkew1 = 0.0;
    matrix->TranslateX = matrix->TranslateY = 0;
}

Matrix MatrixMulti( n, m)
Matrix *n;
Matrix *m;
{
    Matrix mat;

    mat.ScaleX = n->ScaleX * m->ScaleX + n->RotateSkew0 * m->RotateSkew1;
    mat.RotateSkew0 = n->ScaleX * m->RotateSkew0 + n->RotateSkew0 * m->ScaleY;
    mat.RotateSkew1 = n->RotateSkew1 * m->ScaleX + n->ScaleY * m->RotateSkew1;
    mat.ScaleY = n->RotateSkew1 * m->RotateSkew0 + n->ScaleY * m->ScaleY;

    mat.TranslateX = getX(n,m->TranslateX,m->TranslateY);
    mat.TranslateY = getY(n,m->TranslateX,m->TranslateY);

    return mat;
}

Matrix invert(matrix)
Matrix *matrix;
{
    Matrix mat;
    float det;

    det = matrix->ScaleX*matrix->ScaleY-matrix->RotateSkew0*matrix->RotateSkew1;

    mat.ScaleX  = matrix->ScaleY/det;
    mat.RotateSkew0  = -matrix->RotateSkew0/det;
    mat.RotateSkew1  = -matrix->RotateSkew1/det;
    mat.ScaleY  = matrix->ScaleX/det;

    mat.TranslateX = - (long)(mat.ScaleX * matrix->TranslateX + mat.RotateSkew0 * matrix->TranslateY);
    mat.TranslateY = - (long)(mat.RotateSkew1 * matrix->TranslateX + mat.ScaleY * matrix->TranslateY);

    return mat;
}