Rotate Image

The Rotate Image command can rotate an image or image set in 90 degree steps, perform mirror flips, transpose about the main diagonal, and apply free rotation using any precise angle. You also can rotate an image by an angle using the button on the Image Bar.

This Rotate Image command opens from the Image Window > Process > Geometry menu and button on the Main Toolbar. The "immediate" form, shown first, opens when an image or image set is displayed in the top-most window. The general form can be used to select source images from folders, windows, or by matching templates.

Rotate Image Properties
Profile [\|>]	Selects the parameter profile for this command and allows you to save or work with existing presets.
[Select]	Opens the Select Source Images dialog to choose images from an image window, folder, files, name template, or a Mira File List.
Angle .. at	The rotation angle, measured in degrees.
	When Angle is selected, this parameter specifies the center of rotation. You can choose either the center of the image or the centroid coordinate near the center of the image cursor (see section below)
Rotate 90	Check this box to rotate 90 degrees in the positive sense.
Rotate 180	Check this box to rotate 180 degrees.
Rotate 270	Check this box to rotate 270 degrees in the positive sense.
Reverse	Check this box to mirror flip the image in a left/right sense.
Flip	Check this box to mirror flip the image in an up/down sense.
Transpose	Check this box to flip the image about its main diagonal, which extends from pixel [1,1] to the opposite corner.
Centroid	If selecting the Image Cursor option, check this box to have the center of rotation at a centroid position near the center of the cursor. For example, you may want the image rotated about the center of a star.
Edge Replacement	This group specifies how blank pixels are filled with a value when the rotated image exposes blank pixels. Target Value fills the blank area with the specifiedValue. Image Margin fills the blank area with a value typical of pixels along the image margin. Value is the specific value to set when the Target Value option is selected.
Value	The value to assign values to the edge pixels when Edge Replacement = Value.
Resize Image	Check this box to allow the image to be enlarged to hold all pixels after rotation. If this box is not checked, the image size remains the same and the corner pixels rotate outside the visible image.

Choosing the Rotation Point

The image is rotated about a point that can be selected from the following options:

Center: Rotates the image about the center position.
Cursor: Rotates the image using the center of the Image Cursor.

There are two ways to do a Cursor Rotation:

Centroid checked: Rotates about the centroid coordinate near the center of the Image Cursor.
Centroid unchecked: Rotates about the center of the Image Cursor.

If using the image cursor be sure to position it before opening the menu containing this command.

Edge Replacement

The "edge" refers to the blank pixels that rotate into the output image from off the edge of the original image. These pixels have no value but some values must be assigned to them in the rotated image. See these Examples.

Mira provides you 2 options for assigning a value to the edge pixels:

Image Margin: Mira computes a value typical of pixels around the margin of the image.
Value: Mira uses the pixel value you specify in the Edge Value field. This can be an intensity value or a color value. For example, 0 and 500.25 are intensity values, and 255,128,0 is a color value.

Using the Transpose Operation

The Transpose operation reflects pixels across the main diagonal of the image matrix. FITS image have their main diagonal running from the lower left toward the upper right. Other graphics formats have their main diagonal running from upper left to lower right.

Choosing the Rotation Point

Edge Replacement

Using the Transpose Operation

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