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Operations on Bitmaps: Rotating a Picture |
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Rotating a picture consists of changing its angular
orientation. The Image class supports this operation (with somewhat
limited options) through its RotateFlip() method. As mentioned for
mirroring and flipping, the value you pass as argument would determine how
the operation is carried out.
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The members of the RotateFlipType enumeration
that are used to rotate a picture are:
- RotateNoneFlipNone: Nothing would happen
- Rotate90FlipNone: The picture is rotated at 90� clockwise. As
a result, after calling the method with this member, what is on the left
of the original picture would be positioned in the top section of the
picture. Here is an example:
| Original |
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After Calling the Method |
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Notice that, after the method has
been called, the person is still holding the remote control with
his right hand. Here is an example:private void btnRotate_Click(object sender, EventArgs e)
{
Bitmap bmpPicture = new Bitmap("person1.gif");
bmpPicture.RotateFlip(RotateFlipType.Rotate90FlipNone);
CreateGraphics().DrawImage(bmpPicture, 10, 10);
}
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- Rotate180FlipNone: The picture is rotated at 90� clockwise
twice. This means that the picture is first rotated at 90�, then rotated
again at 90�. As a result, after calling the method with this member,
what is on the left of the original picture would be positioned in the
right section but what is on the top would be positioned to the bottom
of the picture. Here is an example:
| Original |
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| After Calling the Method |
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Notice that, after the method has
been called, the person is still holding the remote control with
his right hand. As a result, the remote control is on opposite
sites of the pictures, indicating that it is the same hand.
You can get the same result by calling the method twice with the
Rotate90FlipNone member each time:private void btnRotate_Click(object sender, EventArgs e)
{
Bitmap bmpPicture = new Bitmap("person1.gif");
bmpPicture.RotateFlip(RotateFlipType.Rotate90FlipNone);
bmpPicture.RotateFlip(RotateFlipType.Rotate90FlipNone);
CreateGraphics().DrawImage(bmpPicture, 10, 10);
}
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- Rotate270FlipNone: The picture is rotated at 90� clockwise
three times. This means that the picture is first rotated at 90�, then
rotated again at 90�, and then rotated again at 90�. Here is an example:
| Original |
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After Calling the Method |
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Notice that, after the method has
been called, the person is still holding the remote control with
his right hand.
You can get the same result by calling the
method three times with the Rotate90FlipNone member each
time:private void btnRotate_Click(object sender, EventArgs e)
{
Bitmap bmpPicture = new Bitmap("person1.gif");
bmpPicture.RotateFlip(RotateFlipType.Rotate90FlipNone);
bmpPicture.RotateFlip(RotateFlipType.Rotate90FlipNone);
bmpPicture.RotateFlip(RotateFlipType.Rotate90FlipNone);
CreateGraphics().DrawImage(bmpPicture, 10, 10);
}
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- Rotate180FlipXY: No real change. Actually, the picture is
rotated at 90� four times and then gets back to its original orientation
and position:
| Original |
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| After Calling the Method |
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- Rotate90FlipX: The picture is mirrored, then rotated at 90�
counterclockwise (or rotated at 90� counterclockwise then mirrored):
| Original |
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After Calling the Method |
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=> |
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| Notice that, after the method has
been called, the person is now holding the remote control with
his left hand |
- Rotate180FlipX: The picture is mirrored, then rotated at 180�
counterclockwise twice (or rotated at 180� counterclockwise twice then
mirrored):
| Original |
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| After Calling the Method |
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| Notice that, after the method has
been called, the person is now holding the remote control with
his left hand. As a consequence, the remote control is on the
same side of the screen on both pictures (compare with
Rotate180FlipNone) |
- Rotate270FlipX: The picture is mirrored, then rotated at 90�
counterclockwise three times (or rotated at 90� counterclockwise three
times then mirrored):
| Original |
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After Calling the Method |
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=> |
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| Notice that, after the method has
been called, the person is now holding the remote control with
his left hand |
- Rotate90FlipY: Produces the same result as Rotate270FlipX
- Rotate270FlipY: Produces the same result as Rotate90FlipX
- Rotate90FlipXY: Produces the same result as
Rotate270FlipNone
- Rotate270FlipXY: Produces the same result as
Rotate90FlipNone
- RotateNoneFlipXY: Produces the same result as
Rotate180FlipNone
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