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rot_shift2D - Rotate, shift, mirror, and scale a 2-D image.

Usage

output = rot_shift2D(image, alpha, sx, sy, mirror, scale, interpolation_method)

Input

image
input image
alpha

in plane rotation angle (Note this angle is different from Euler in plane angle psi). Check I_O about 2D & 3D alignment parameter related conventions

sx
2-D x shift
sy
2-D y shift
mirror
0. does not mirror 1. mirror over x-axis
scale

re-scale size ratio after applying rotation. The scale will change the 'physical pixel size' of the image (scale >1 will reduce the pixel size, scale<1 will increase it). Note re-scaling will not change the image size in pixels; to do that, use command resample.

• Attention: scale cannot be set as 0.
interpolation_method
interpolation method used to transform the image (default is set to "quadratic" in global_def.py).

Output

output
the transformed image

Method

The rotation is performed first, second the shift (in one interpolation step). The scale will change the 'physical pixel size' of the image (scale >1 will reduce the pixel size, scale<1 will increase it). Note rescaling will not change the image size in pixels; to do that, use command resample.

Options

interpolation_method
• "linear" use linear interpolation to sample the rotated image
• "gridding" use gridding to sample the rotated image ( This method is very slow )

Description

• The rotation, shift, and scaling are achieved using the following procedure:
• Construct a transformation matrix (a class objection of C++ or python) from the in_plane angles through Transform3D.
• set translation attribute of the object to take care of translation shifts.
• set scale attribute of the object to include scaling factor.
• apply the class object to input image.
• See P. R. Baldwin et al. below to find out how to construct transformation class.

Zhong Huang

category 1
FUNDAMENTALS

fundamentals.py