To open the Resampling Preferences page,
click 
on the Image Registration toolbar and
select the Resampling tab.
Resampling Preferences
Use this page to configure the way images are re-sampled. This page also selects which transformation is being used to achieve registration.
To open the Resampling Preferences page,
click on the Image Registration toolbar and
select the Resampling tab.
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Transformation |
Specifies the mathematical mapping between the marker coordinates in the reference image and the target images. Shift: Corrects a coordinate displacement in the x and y directions. Shear: Corrects coordinate displacements, rotation, non-perpendicular axes, and unequal scale in the x and y directions. |
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Resampling method |
Specifies the method used to compute image intensity at fractional pixel coordinates. Bi-linear: Computes a linear interpolation between pixels in the x and y directions. Bi-cubic: Computes a 4 term cubic polynomial interpolation between pixels in the x and y directions. Nearest Neighbor: Uses the pixel nearest to the transformed coordinate instead of re-sampling the pixel values. This inflates the FWHM by about 0.3 pixels but preserves the noise structure of the image, which can have important consequences when aperture photometry or image cleaning will be done on the registered images. |
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Reference Image |
Select the reference image onto which the transformation mapping is computed. This image is not resampled. |
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Residuals |
Opens a window listing a table of residuals that result from the transformation equations. The residuals show the distance, in pixels, between the marker points and their predicted positions in the registered images. This can be used to spot bad points that can give a bad transformation solution and should be deleted before the transformation is recalculated without them. |
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Conserve Flux |
Check this box to conserve flux (sigma per unit time) in the transformation equations. For example, if conserving flux and the output pixel is 1/2 as wide and 1/2 as tall, then the signal is 1/4 as high. |
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Save Undo Copy |
Check this box to save an Undo copy of each image before registration is done. This allows you to recover the original images if you want to re-do the registration. Uncheck this box to save memory, which can be a critical issue when registering many, large images that may need all the memory available on the computer. |
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Verbose |
Check this option to give verbose listing of registration results. |
Use the Shift transformation when there is no significant rotation or scale difference between the images.
Use the Shear transformation then there are scale differences and/or rotational differences between the images.
Use the Bi-cubic resampling option when images have sharp features and many point sources.
Use the Bi-linear option if the bi-cubic filter leaves ringing artifacts. The bi-linear kernel is less sensitive to sharp points but applies more smoothing to the image. For most images, you should choose the Bi-cubic filter.
Use the Nearest Neighbor resampling option if you need to preserve the noise structure in the image, as before using the Aperture Photometry package, MExtract package.
