Makes an internal copy of this matrix, which is inverted
and then used to transform the point
(x, y)
to the corresponding point,
(sx*x + shx*y + tx, sy*y + shy*x + ty)
which are the coordinates of the
Point
returned by
itransform.
If this matrix has no inverse
NULL
is returned.
When
itransform
is called with a
Point
as the argument the transformation is applied to the point
(p.x, p.y)
and the result is returned as the coordinates of a new
Point.
Two different transformations are applied when
itransform
is called with a
Rectangle
as the argument.
The corner of that rectangle is transformed as described above,
the equivalent of
idtransform
is applied to
(r.width, r.height)
and the two results are combined in a new
Rectangle
which is the value returned by
itransform.
The values of
sx,
shx,
tx,
sy,
shy,
and
ty
used in the transformation are the obtained from the inverted matrix.
We often refer to this as a transformation from "device space" to
"user space", despite the fact that the original point may not
have anything to do with a physical device, like your screen.
| |
| Example: |
The program,
import yoix.*.*;
JWindow f = {
Color background = Color.red;
Point location = {
double x = 72;
double y = 72;
};
paint(Rectangle rect) {
Point ul;
Point lr;
graphics { // "named block"
gsave();
ul = itransform(2, 2);
lr = transform(size.width, size.height);
lr.x = lr.x - 2;
lr.y = lr.y - 2;
lr = itransform(lr);
moveto(ul.x, ul.y);
lineto(ul.x, lr.y);
lineto(lr.x, lr.y);
lineto(lr.x, ul.y);
closepath();
setrgbcolor(0, 0, 1);
fill();
grestore();
}
}
};
f.visible = TRUE;
uses
itransform
and
transform
to help fill a blue rectangle that lies exactly 2 pixels from the edge
of a window that has a red background.
| | |
| Return: |
Point
| | |
| See Also: |
concat,
concatmatrix,
currentmatrix,
dividematrix,
dtransform,
Graphics,
identmatrix,
idtransform,
initmatrix,
invertmatrix,
maptopixel,
rotate,
scale,
setmatrix,
shear,
transform,
translate
|
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