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LibreLogo is an integrated development environment (IDE) for computer programming in the programming language Python, which works like the language Logo using interactive vector turtle graphics. Its final output is a vector graphics rendition within the LibreOffice suite. It can be used for education and desktop publishing.
Turtle graphics are often associated with the Logo programming language. [2] Seymour Papert added support for turtle graphics to Logo in the late 1960s to support his version of the turtle robot, a simple robot controlled from the user's workstation that is designed to carry out the drawing functions assigned to it using a small retractable pen set into or attached to the robot's body.
Logo's most-known feature is the turtle (derived originally from a robot of the same name), [5] an on-screen "cursor" that shows output from commands for movement and small retractable pen, together producing line graphics. It has traditionally been displayed either as a triangle or a turtle icon (though it can be represented by any icon).
Features may be specific structures in the image such as points, edges or objects. Features may also be the result of a general neighborhood operation or feature detection applied to the image. Other examples of features are related to motion in image sequences, or to shapes defined in terms of curves or boundaries between different image regions.
The Canny edge detector is an edge detection operator that uses a multi-stage algorithm to detect a wide range of edges in images. It was developed by John F. Canny in 1986. Canny also produced a computational theory of edge detection explaining why the technique works.
To improve the corner detection ability of the differences of Gaussians detector, the feature detector used in the SIFT [20] system therefore uses an additional post-processing stage, where the eigenvalues of the Hessian of the image at the detection scale are examined in a similar way as in the Harris operator. If the ratio of the eigenvalues ...
The vertical edges on the left and right sides of the circle have an angle of 0 because there is no local change in . The horizontal edges at the top and bottom sides of the circle have angles of − π / 2 and π / 2 respectively because there is no local change in . The negative angle for top edge signifies the transition is ...
In (Lindeberg 2013b, 2015) [2] [3] it is shown that there exist other scale-space interest point detectors, such as the determinant of the Hessian operator, that perform better than Laplacian operator or its difference-of-Gaussians approximation for image-based matching using local SIFT-like image descriptors.