Translation
Some applications translate (or shift) objects drawn in the client area. If
your application features this capability, use the
SetWorldTransform function to set the appropriate world-space to page-space transformation.
This function receives a pointer to an
XFORM structure containing the appropriate values. The
eDx and
eDy members of
XFORM specify the horizontal and vertical translation components, respectively.
When
translation occurs, each point in an object is shifted vertically, horizontally, or both,
by a specified amount. The following illustration shows a 20- by 20-unit
rectangle that was translated to the right by 10 units when copied from world
coordinate space to page coordinate space.
In the preceding illustration, the x-coordinate of each point in the rectangle
is 10 units greater than the original x-coordinate.
Horizontal translation can be represented by the following algorithm.
x' = x + Dx
Where
x' is the new x-coordinate,
x is the original x-coordinate, and
Dx is the horizontal distance moved.
Vertical translation can be represented by the following algorithm.
y' = y + Dy
Where
y' is the new y-coordinate,
y is the original y-coordinate, and
Dy is the vertical distance moved.
The horizontal and vertical translation transformations can be combined into a
single operation by using a 3-by-3 matrix.
|1 0 0|
|x' y' 1| = |x y 1| * |0 1 0|
|Dx Dy 1|
(The rules of matrix multiplication state that the number of rows in one
matrix must equal the number of columns in the other. The integer 1 in the matrix |x
y 1| is a placeholder that was added to meet this requirement.)
The 3-by-3 matrix that produced the illustrated translation transformation
contains the following values.
|1 0 0|
|0 1 0|
|10 0 1|
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