Description of Find Object Plugin

As in the standard OpenCV FindObj program, there are 5 detector methods and 2 matcher methods which can be selected. They detect features and match them as a rectangular projection. The matched region will be overlayed with a replacement image if replace object is enabled. This is done using a variety of feature detectors and region matches. The match works by creating sets of Feature points. These points are generated for both the source and reference object frames. Then the two sets are matched for Homography (a regional similarity).


Fast Library for Approximate Nearest Neighbors
(flann not selected) Brute Force

Detectors Algorithm

Scale-Invariant Feature Transform
Speeded-Up Robust Features Be aware that Surf is non-free and has been removed from versions of OpenCV being built. If you have used it in a past project, it could result in a SEGV crash.
Oriented fast and Rotated Brief
Accelerated Keypoint detector And descriptor Extractor
Binary Robust Invariant Scalable Keypoin
Don’t Calculate
Do nothing

The CINELERRA-GG plugin has several additional features for ease of use and more flexibility. A description of parameters is outlined below.

to get back to the default values.
detector selections as described above.
Replace object:
checked if replacing the object is the desired outcome.
use the Matcher, or if unchecked just use brute force.
Draw match:
will display a blue line around the matching object only for the purpose of verifying the placement. The starting point for the box is designated by a white outlined circle in corner #1.
Scene/object/replace layer:
number designating the attachment track of each findobject plugin element.

After matching, the resulting projection corners are used to do reshaping. The general procedure is:

Selectable specifications

when set, the matching aspect ratio is applied, otherwise the original object aspect is applied.
when set, the match surface area is used for scaling, otherwise the original surface area is used.
when set, the match orientation is used in the projection, otherwise the original orientation is used (orthonormal).
when set, the match replacement is centered to the projection center, otherwise the original object center is used.

Once the replacement corners are calculated, the replacement object is overlayed to the scene frame.

Scene/Object/Replace Drag
only 1 can be checked on at a time (and that includes counting the Title plugin drag box). The Drag boxes are faster alternatives to using the column dials.
Scene/Object/Replace columns of X/Y/W/H
x and y positions along with width and height; 0÷100% + Replace ΔX and ΔY deltas for the Replace column.
Draw keypoints
when enabled shows the detection points created by the feature detection and used in the matcher Algorithm calculation.
Draw scene/object/replace border
displays each of the borders which helps to determine correctness.
Object blend amount
can dampen (smooth) the corner motion from frame to frame to reduce jitters.

The CINELERRA-GG Community, 2021