Traditional diagram editors require the user to select the different available shapes from a list before placing them on the drawing area. In contrast, sketching allows the user to really draw diagrams like with pen and paper. The actual shapes are later recognized by software. This means an increased flexibility and simplicity in graphical user interfaces. We present a new approach towards ske...

This paper describes the design, features and advantages of a drawing application -the L.E.C.G.O-Paint applicationthat is part of a constructivist multi-representational computer environment designed for beginners’ learning of Programming and C (the LECGO environment; Kordaki, 2007). L.E.C.G.O-Paint supplies tools that provide support for students to express their own intuitive graphical soluti...

In this paper we consider the problem of drawing a planar graph using circular arcs as edges, given a one-to-one mapping between the vertices of the graph and a set of points in the plane. If for every edge we have only two possible circular arcs, then a simple reduction to 2SAT yields an O(n) algorithm to find out if a drawing with no crossings can be realized, where n is the number of vertice...

The location of imperfections or heterogeneities in shapes and contours often correlates with points of interest in a visual scene. Investigating the detection of such heterogeneities provides clues as to the mechanisms processing simple shapes and contours. We determined set-size effects (e.g., sensitivity to single target detection as distractor number increases) for sampled contours to inves...

We study scaling limits of random permutations (“permutons”) constrained by having fixed densities of a finite number of patterns. We show that the limit shapes are determined by maximizing entropy over permutons with those constraints. In particular, we compute (exactly or numerically) the limit shapes with fixed 12 density, with fixed 12 and 123 densities, with fixed 12 density and the sum of...

Euler diagrams are an accessible and effective visualisation of data involving simple set-theoretic relationships. Efficient algorithms to quickly compute the abstract regions of an Euler diagram upon curve addition and removal have previously been developed (the single marked point approach, SMPA), but a strict set of drawing conventions (called well-formedness conditions) were enforced, meani...

Continuous Line Drawing (CLD) is a drawing style where a picture consists of a single closed non-intersecting line. This paper presents an automatic algorithm for constructing CLDs, with tone and structural information obtained from input images. The connectivity of the line is maintained through a tree generated by path finding with consideration of the key features for a given image. A branch...

In the typical population, a series of drawing strategies have been outlined, that progressively emerge during childhood. Individuals with Williams syndrome (WS), a rare genetic disorder, produce drawings that lack cohesion, yet drawing strategies in this group have hitherto not been investigated. In this study WS and TD groups drew and constructed (from pre-drawn lines and shapes) a series of ...

Given two binary phylogenetic trees covering the same n species, it is useful to compare them by drawing them with leaves arranged side-by-side. To facilitate comparison, we would like to arrange the trees to minimize the number of crossings k induced by connecting pairs of identical species. This is the NP-hard Tanglegram Layout problem. By providing a fast transformation to the Balanced Subgr...

A binary tanglegram is a pair 〈S, T 〉 of binary trees whose leaf sets are in one-to-one correspondence; matching leaves are connected by inter-tree edges. For applications, for example in phylogenetics, it is essential that both trees are drawn with no edge crossing and that the inter-tree edges have as few crossings as possible. It is known that finding a drawing with the minimum number of cro...