The Add/edit warp points check box can be used to warp the image, using local shifts at a set of points called control points. Once this is turned on, the only transformation parameter that can be changed is the shift of the current control point. See the Warping Images section of the man page for a description of using warping.
The Arrow buttons allow each transformation parameter to be changed by a selected increment. There is an additive increment for translation, an independent increment for rotation angle, and a multiplicative factor for magnification and stretching.
The Stretch Angle slider sets the axis along which the section will be stretched by either an Arrow button or a hotkey. This axis is shown by the red dashed line. If the section has already been stretched, the axis of that actual stretch is shown with a blue dashed line.
Rotation, magnification, and stretch will occur around the center of rotation, which is marked by the yellow star. You can use [Ctrl]+Middle-Mouse-Button to move this center to a point that you want to keep fixed during further changes of the transformation. You can also set up a second fixed point using [Ctrl]+Right-Mouse-Button, after which stretching with the mouse will keep both the center and this fixed point at constant positions.
Correcting image stretch can be nonintuitive when done just with a regular stretch. Here is a procedure to follow using stretching with a second fixed point:
The same thing can be accomplished in a similar way by adding only 3 warping points, which still leaves just a linear transformation.
The Cross-Correlate button can be used to align the images by cross-correlating them in a square area around the center point marked with the yellow star. The program will search for peaks in the cross-correlation of padded and filtered extracts from the two images, then evaluate the correlation coefficient for peaks within a certain range of the origin and pick the peak with the highest correlation. The size of the region being correlated can be set in the Box spin box, and the limit on the shift in X and Y that can be found is adjusted with the Limit spin box. These shifts are incremental to the current translation between images, so if you adjust the translation approximately, the correlation should be able to find a small shift to refine your translation. The parameters for padding and filtering are based on the settings that are most successful in Blendmont when finding overlaps between adjacent pieces.
The extent of the area being correlated is shown temporarily when any of the related controls are used. The box is drawn in yellow when the size or shift limit is adjusted; it is drawn in green after a correlation that succeeds in giving a peak and in red when the correlation fails to yield a peak within the shift limit.
Below the cross-correlation controls are some buttons that become active when there are more than 3 warping points, and that may be useful when reading in a warping transformation computed by cross-correlation. The Biggest button will select the warping point that has the largest shift. The down and up arrows will move from the currently selected warping point to the one with the next lower or next higher shift. Turn on the Draw warp vectors checkbox to see a line representing the amount of shift at each warp point.
If the program was started with "-a" to specify a Global rotation angle, this angle is displayed and can be adjusted with the spin box below the Stretch Angle slider. Use the up and down arrows to adjust the angle by 1 degree, or type in a new value directly. Select Mouse shifts X only to constrain translation changes with the mouse to the X direction in the rotated images. With this constraint, it is still possible to change the shift in Y with the arrow hot keys or the Y translation arrow buttons.
If the program was started with "-t" and a file of tilt angles, then two more
controls appear. Select Apply cosine stretch to stretch the current
image along the X axis by the ratio of the cosines of the current and
reference image tilt angles. They should be easier to line up with this
stretching. Below this checkbox is the Tilt angle offset spin box to
allow you to adjust the tilt angles by a constant amount. For very high tilt
angles, this offset may be needed to get the right amount of cosine stretching.
In the top panel, the X and Y radio buttons can be used to select which type of
edge, if there is more than one type of edge in a section. The edge number is
displayed in a spin box and can be changed by typing a new number into the text
box or by pressing the up and down arrow buttons. In addition, the position
within the montage of the
lower piece of an edge is displayed in X and Y spin boxes; these piece
positions are numbered from 1. These spin boxes provide a more convenient way
to know where an edge is and navigate between edges, such as to see all of the
edges around a particular piece.
The Exclude edge checkbox allows you to exclude an edge from further
consideration both in Midas and in Blendmont.
If you excluded edges with a model file when running Blendmont, it will
already be marked as excluded here. When the next checkbox,
Skip excluded edges,
is on, the program will skip over excluded edges
when you move between edges with the controls, and it will omit these edges
from any error computations (see below).
If you excluded any edges with a model, this option will be turned on by
default; otherwise, you need to turn it on when you first exclude edges.
Turn this option off to go to any of
these edges in order to include them again and adjust their displacements.
Only X and Y translations of one piece relative to another can be changed when
fixing montages.
Cross-correlation can be used when fixing edges; it may be more successful
than the correlation within Blendmont because you can select the center of the
area to correlate. The area correlated
corresponds to the intersection of the region where the two pieces overlap and
the square correlation box shown on the screen.
The bottom panel displays information about the errors in fitting pieces
together with the current displacements and allows one to go to the edges with
the highest error. An error is the difference (or distance) between the
displacement between pieces implied by the X and Y translation values at that
edge, and the displacement achieved when all pieces are shifted into best
alignment using the translation values for all of the edges.
For the edges with the six highest errors, the edge number and error are
displayed in a button, which can be pressed to make that edge be the current
edge. The errors, and even the edges, displayed in these buttons will change
whenever the displacement at the current edge is changed. You can select the
number of buttons to display (between 2 and 10) with the "-e" option when
starting the program.
Below the buttons are the X and Y components of the error at the current edge.
On the line below that is the "Leave-out" error for the current edge, which is
its error when its translation values are left out when solving for the best
fit between pieces. This error can be compared directly with any mismatch
observed between the pieces. Pressing the Apply Leave-out Error button
will change the X and Y translations by these amounts.
When there are more than 10 pieces, the program can do robust fitting to
eliminate outlying displacements from the estimation of piece shifts. This
procedure is enabled with the Robust fits checkbox, which is on by
default. It will accentuate the errors of the outliers when there are many
pieces and make it easier to find these edges and either exclude them or fix
their displacements. A spin box allows the criterion for outlier elimination
to be adjusted. See the man page for more details.
When there are over 625 pieces, the errors are estimated using local patches
of pieces in order to save time, so they may not exactly match the values in
Blendmont. With many thousands of pieces, the error computation may
noticeably slow down the program when moving between edges. There is a
checkbox, Skip error computation, to avoid this delay when browsing
through edges.
File Menu Items
Edit Menu Items
Controls when Fixing Montages
X edges are between adjacent pieces in a row and are numbered from left to
right in the bottom row, next row, etc. Y edges are between adjacent pieces
in a column and are numbered from bottom to top in the left-most column, next
column, etc. Every edge can also be identified by its lower piece, namely the
piece to the left of an X edge and below a Y edge.