GIMP GRADIENT MAGNITUDE CODE

qCPDI for 'quadratic' CPDI: this method uses linear grid shape functions and additionally maps midpoints of edges to nodes ( e.g., 8 node element in 2D) resulting in an isoparametric element with quadratic shape functions.lCPDI for 'linear' CPDI: this method uses linear grid shape functions and maps the corners of the domain to a single linear element (4 node element in 2D and 8 node element in 3D) resulting in an isoparametric element with linear shape functions.The subclasses of this method depend on grid shape functions being used and on the finite element types used to map that particle domain:

When using this approach, an initial 2D rectangle domain deforms to a parallelogram and an initial 3D orthogonal box deforms to a parallelepiped. If r j0 is a vector from the particle to any edge location j in the undeformed domain, then r j = F pr j0, where F p is the deformation gradient on the particle, is the vector to that location in the deformed domain. The version of CPDI available here finds the corners of the deformed domain using the deformation gradient on the particle.

Integrals over the deformed domain can then be evaluated to give S pi and G pi in terms for N i(c j).

Where c j are nodes of the deformed particle domain ( e.g., usually corners of the domain) and M j(x) are isoparametric finite element shape functions for the elements used to discretize the deformed particle domain. In the most generalized description of MPM (called GIMP for General Interpolation Material Point ), the shape function (S pi) and shape function gradient (G pi) for extrapolation from node i to particle p are: These extrapolations are controlled by 'Shape Functions,' and the various MPM methods correspond to various methods for evaluating the shape functions. Many tasks in MPM involve extrapolations from particles to the grid or from the grid to particles.

GIMP GRADIENT MAGNITUDE CODE

Where can I find the code for the Gimp Image Gradient plugin so I can learn something from it? I am not interested in the other Gimp plugins for edge detection (I verified that they are not quite as good as the Image Gradient, at least for my application). The problem is that my C++ code is less sensitive to small gradients than the Gimp plugin is, as can be seen from the other two images below. The difference in luminosity between two adjacent rings increases from 2 luminosity units (for the inner rings) to 30 luminosity units (for the outer rings) in the outward radial direction.Īs expected, the detected gradient is small for the inner rings and higher for the outer rings. The test image consists of some 13 circular rings with various luminosities (constant for each ring). gradient intensity), although my work is in color as well. Mouse hover says 'Compute gradient magnitude and/or direction by central differences'.īelow I embedded a gray test image to compare the results (i.e. The plugin I am referring to is under Filters/Edge-Detect/Image Gradient in Gimp 2.10.8. My code works well but is not as good as a specific Gimp plugin, especially when detecting more faint edges (low luminosity gradient). I wrote a C++ code where I perform edge detection on color or gray images (ppm files).

Gimp gradient magnitude