Sum of Squared Differences

The Sum of Squared Differences (SSD) is a way of determining the correlation between two image regions. It is usually involved when motion compensation needs to be done. SSD is defined as followed: There are some variations of SSD. Like the Zero-mean Sum of Squared Differences (ZSSD): See also:

[Note] floating-point/fixed-point operations versus OpenGL

From the Android NDK example "bitmap-plasma": We're going to perform computations for every pixel of the target bitmap. floating-point operations are very slow on ARMv5, and not too bad on ARMv7 with the exception of trigonometric functions. For better performance on all platforms, we're going to use fixed-point arithmetic and all kinds of tricks I […]

Review: "Parallel Tracking and Mapping on a Camera Phone"

Based on the PTAM Project (here PTAM-d for PTAM running on a desktop computer), which originally runs on a computer, Klein and Murray adapted the code to run on an iPhone 3G (here PTAM-m for PTAM running on mobile device such as smartphone). Of course everything need to become more light-weighted so that it can […]

Shi-Thomasi Corners

Shi-Thomasi is a corner detection algorithm improved from Harris' corner detector. The improvement is the way how a certain region within the image is scored (and thus treated as corner or not). Where the Harris-corner detector determines the score with the eigenvalues and of two regions (the second region is a shifted version of the […]