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Bilinear Warping
There are three bilinear methods for image warping available.
All methods use same bilinear geometric transform technique, but with different Strength factor.
Exception is Move method which is not limited by warping line, but applies to whole image.
Smear and Smudge methods are limited to warping line and only difference between them
is Strength factor which is preset to 200 for Smear and to 110 for Smudge.
All three methods are very suitable for fascial deformations.
Strength factor is actually the value that shows how wide warping action will apply. Higher value will
perform wider warping action. You can change the strength factor to desired value.
Warping length is the length of line you draw on the image by holding pressed left mouse key and
moving the mouse to an arbitrary point. When mouse key is released, warping will be applied in such a way
that pixel at starting line point will be moved to line ending point, while position of neighbor pixels will be
calculated according to method chosen.
Trigonometric Warping
There are eight methods that apply trigonometric warping technique. First four methods use warping line,
while others use warping circle to define the amount of warping applied. Strength factor
in trigonometric warps acts as a pulling/pushing strength.
Ripples
method creates ripples on the whole image. The amplitude of each ripple depends on the length of
warping line. Also, if warping line is drawn straight upward or downward, ripples will be horizontally distributed,
but in the last case, amplitude will be shifted for half a cycle. If warping line is drawn streigh to left or right,
ripples will be vertically distributed. All other directions are combination of those two methods.
Long Ripple
is a method that applies a single ripple across the image. The same warping line technique is used
like in previous method.
Balloon
effect applies limited ripple effect depending on the warping line. When the line is drawn straight from left to right,
the desired are calculated from its length is squeezed.
Double baloon
doubles baloon method. When line is drawn from left to right, middle part is squeezed, while upper
and lower parts are stretched.
Splash
method simulates a water splash. The trigonometric transform is applied in Z direction and rendered in
two dimensional image. Splash, Blob and Blub method use warping circle
instead of warping line to obtain desired effect.
Blob
method simulates pushing the desired circular region along Z axis toward the viewer.
Blub
method uses the same technique as above, except that the region is pushed outward, i.e. from the viewer in
negative Z direction.
Balloon, Double Balloon, Blob and Blub methods are specially designed for
fascial deformation, as you can see from the examples.
Waves
method gives a vawy look to an image by selecting horizontal or vertical vawes from pop-up menu (right mouse click on IMA).
Amplitude and vawe length is determined by x and y component of warping line. If vertical vawes are selected,
y component of warping line specifies amplitude of a vawe while x component specifies wave length. The same
rule applies for horizontal vawes, but this time x component specifies amplitude while y component is used as vawe length.
Twirling
Twirling effect is already well known in image deformations. Pixopedia_24 has three different twiring methods,
that applies so called water sink effect. Twirling angle ranges from 0 to 180 degrees if warping line
has positive Y component and from 0 to -180 degrees if warping line has negative Y component.
Inside Twirl
effect twirls the region of image calculated from warping line length. The outer part of picture is
not affected.
Outside Twirl
is similar to inside twirl, except that calculated region is only rotated, while the rest of picture is twirled.
Full Twirl
is ordinary twirl that applies to whole image.
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ROI Warp
ROI warping performs warping image or selected rectangle ROI to some general convex quadrangle.
Strength factor does not have any effect on this action. Deformations are controlled via
warping polygon.
Warping polygon is created either by pressing Set ROI to image on pop-up menu
(ROI is set to whole image) or simply by drawing ROI rectangle on desired part of picture.
After rectangle is placed, four control points replace rectangle corners.
Starting rectangle determines which part of picture will be warped.
To create final quadrangle, move contol points where you want.
When you pass with cursor over some control point, cursor shape is changed to pointing hand.
Pop-up menu is called by pressing the right mouse button.
This menu has two submenues: warp method and movement settings.
You can choose what warping method to use (perspective, bilinear) and how to perform
warping polygon points movement.
You can move control point free or move it with some restrictions:
fixed length, mirror, fixed points, diagonal mirror, etc..
To apply warping, select Apply on pop-up menu. Apply Full House selection
performs multiple warping of selected ROI to obtain effect of looking inside some warped room
with walls filled with selected ROI.
Random
There are two random methods available:
explode and movement.
Explode
method simply remaps pixels from original image to some different randomly choosen location.
Maximal distance from original image possition is determined by warping line length
and strength factor.
Motion
method is similar to previous method except that pixels are distributed randomly in
direction of warping line. By this method we get something like non-blured motion effect.
Waves
method performs wave warping. You can select (right mouse click) between horizontal or vertical
waves direction. Waveing is performed by draing a line onto image.
Wave amplitude is determined by line length and line angle is used to calculate wave length.
BackFill
After performing perspective or random warping, the rest of picture is filled with Background
color if BackFill check box is checked. Otherwise warped ROI is placed on existing picture.
Antialiasing
By default Antialias check box is checked. This results in pixel interpolation after warping, which gives
smoother warped image. When unchecked, image is zigzagged, but it can be used to obtain
some special effects.
NOTE:
Resultant image is affected by all previously set
Global parameters.
Example of warp usage.
In the upper left corner is original picture, other pictures are warped.
Click on picture to enlarge.
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