ImaLab
Generating C++ Modules
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Computing and Analyzing Difference Images
The diff-plugin demonstrates the functionalities of the segmentation module .
Processing Steps
The binary difference image between the current image and the reference image is computed, and run-length encoded (class RLEImage). The reference image is the n-th image preceding the current image, as specified by the variable ref-delta.
Connectivity analysis is then carried out on the difference image, yielding a list of regions, sorted by size.
Display Step
The difference image is displayed in screen position 1. For each connected region (larger than min-size), we display
- the x-y-bounding box, color orange
- the center of gravity
- the first point encountered during image scan
Speeding up the computation.
The difference computation samples the images according to the variables x-step, y-step. Tuning these values, you can trad speed for quality. A region is guaranteed to be found if its extension is greater than the sample step.Globals and Modifiable Parameters
The following parameters can be consulted and modified during experimentation:
- x-step horizontal sampling step
- y-step
- thresh1 Threshold for red channel
- thresh2 Threshold for difference
- ref-delta distance to reference image
- min-rsize minimum region size
- connexity 0 means 4-connexity, 1 is 8-connexity
In order to modify one of the first 4 parameters, use the function:
RLEImage::SetParams(x-step,y-step,thresh1,thresh2)
The following global variables reflect the current state of the program:
- imaref
- rle
- imgrefs
- region-list
- region-list0