Line-drawing Methods Research Articles

Generation of cartoon-style bas-reliefs from photographs

This paper describes a new algorithm that generates a cartoon-style bas-relief surface from photographs of general scenes. Most previous methods for bas-relief generation have focused on accurate restoration of input 3D models on a background plane. The generation of bas-reliefs with artistic effects has rarely been studied. Considering that non-photorealistic rendering (NPR) techniques are currently very popular and 3D printing technology is developing rapidly, extending NPR techniques to the generation of a bas-relief surface with artistic effects is natural and valuable. Furthermore, cartoon is a basic non-realistic and artistic style familiar to general users. From this motivation, our method focuses on generating a cartoon-style bas-relief surface. We use the lens blur function of Google Camera, which is a smartphone application, to obtain a photograph and its depth map as inputs. Using coherent line drawing and histogram-based quantization methods, we construct a depth map that contains the salient features of given input scenes in abstract form. Displacement mapping from the depth map onto a thin plane generates a cartoon-style bas-relief. Experimental results show that our method generates bas-relief surfaces that contain the characteristics of cartoons, such as coherent border lines and quantized layers.

Raisz’s physiographic method of landform mapping

Maps are powerful modes of communication between scientists and novices. Cartographer Erwin Raisz understood just how powerful maps could be for visualizing the broad landscape. His physiographic method of landscape representation merged pictorial representation with large-scale cartography to generate some of the most vivid images of the physical landscape in the early part of the 20th century. Today, despite our ability to represent the landscape with increasingly realistic representations, there is a fondness for those traditional style line drawings. Thus, it is important to take time and reflect on the impact of Raisz’s physiographic map on modern terrain representation. Here we look at Raisz’s own body of work and his influence on modern cartographers, and finally we look at non-photorealistic representation’s potential for replicating early line drawing methods like Raisz’s.

Comparison of Manufacturer‐Recommended Exposure Durations with Those Determined Using Biaxial Flexure Strength and Scraped Composite Thickness Among a Variety of Light‐Curing Units

Manufacturer-recommended exposure durations for light-curing units are often understated and might not have true clinical relevance. To compare composite depths of cure among exposure durations provided by the manufacturer and those obtained when optimizing exposure duration for biaxial flexural strength or for composite compule-scraping tests when using different light-curing units. A hybrid composite (Prodigy, A3, Kerr, Orange, CA, USA) was exposed to different light-curing units (all manufactured by Kerr Demetron) (conventional quartz-tungsten-halogen [QTH], conventional blue light-emitting diode [LED(CONV)] or a high-intensity blue LED light [LED(HIGH)]) for various amounts of time, including that recommended by the manufacturer for the given light. A test model was designed in which 0.5-mm thick composite discs were stacked between Mylar sheets to a total composite thickness of 3.0 mm. The top of each stack was exposed to the different lights for a variety of exposures at a 2-mm distance. Twenty-four hours later, the stacks were disassembled, and the individual discs from each 0.5-mm thick increment were tested for biaxial flexure strength. Ten discs were made for each exposure duration from each light. Statistical analysis (analysis of variance, Dunnett-Hsu post hoc test, alpha = 0.05) was used to identify the exposure duration needed for the flexural strength at a 2.5-mm depth (manufacturer-recommended thickness) to be similar to that at the topmost 0.5-mm thick increment. Compules of the same composite were modified to form cylinders in which their contents were forced to one end and photopolymerized (at a 2-mm distance) for a variety of exposure durations using the same light units mentioned above (N = 5). Twenty-four hours later, compule contents were extruded, and the unpolymerized residue was removed using hand scraping with a plastic spatula. The thickness of the resulting specimen was measured, and was plotted as a function of exposure duration for each light. Regression analysis was applied to generate the mathematical correlation between exposure duration and resulting composite scraped thickness. Manual line-drawing methods were used on that generated plot to determine the major inflection in the exposure-thickness relationship that changed, and the exposure time correlated to that inflection point was considered the optimal exposure duration from this method. Manufacturer-recommended exposures for a 2.5-mm thick composite increment from the lights used were: QTH 20 seconds; LED(CONV) 10 seconds; and LED(HIGH) 5 seconds. Flexural strength and scraped composite compule thickness values markedly changed with increase in exposure duration and differed among the lights. Exposure durations needed to provide similar flexural strength at 2.5 mm as that of the topmost increment were: QTH 30 seconds; LED(CONV) 15 seconds; and LED(HIGH) 20 seconds. Exposure durations derived from inflection points of the scraping plots provided optimal exposure duration values of: QTH 25 seconds; LED(CONV) 15 seconds; and LED(HIGH) 17 seconds. In all cases, use of manufacturer-recommended exposure duration provided a lower flexural strength or scraped composite thickness than did longer exposures used. Exposure durations using the simple scraping method correlated very well with those of the much more sophisticated biaxial test. No one can provide a clinician with the optimal exposure duration to use for a given light and a specific lot, shade, and brand of composite. Instead, manufacturers offer a single exposure that is meant to be used for all clinical scenarios and operating conditions. The results of this test indicate that manufacturer-recommended exposures proved inadequate to optimize the flexural strength of the recommended increment of composite, but longer exposures were required. The exposure durations determined from the much more simplified composite compule-scrape test proved to match those found to optimize biaxial flexure testing for each light used. Clinicians can thus adapt this very simple in-office scraping test to develop their own customized exposure guide, providing them with exact exposure durations that will optimize composite properties, thus eliminating the guesswork from this most important aspect of chairside dentistry.

Further reliability analysis of the Harrison radiographic line-drawing methods: Crossed ICCs for lateral posterior tangents and modified Risser-Ferguson method on APViews

Objective: To determine whether the newly derived interclass and intraclass correlation coefficients (ICCs)would overstate or understate the results from 2 previously published studies, which used better known ICCs that assume nested factors, and to determine mean absolute differences of observers' measurements for 3 previous studies. Study Design: Retrospective analysis of data from 2 blind studies with repeated-measure design. Two newly derived ICCs, appropriate to situations with 3 random factors (patients, examiners, and occasions) that bear a crossed (as opposed to nested) interrelationship, were applied to data from an experiment with random crossed factors. Main Outcome Measures: Observer reliability is determined with ICCs, 95% CIs, and observer error analysis (mean absolute differences of observers' measurements) for angles and distances derived from Harrison's modified Risser-Ferguson line-drawing method on anteroposterior (AP) lumbar and AP cervical radiographic views. Observer error analysis for angles and distances derived from Harrison's posterior tangent method on lateral cervical views was also determined. Results: The majority of ICCs for reliability of line drawing on both AP cervical and AP lumbar radiographs were in the high range; 13 of 16 ICCs were greater than 0.88. The other 3 ICC values (0.61, 0.76, 0.78) concerned determining the sacral base on AP lumbar views. The new ICCs underestimated observer reliability compared with previously published results (intraclass ICCs lower by 0.01-0.02 and interclass ICCs lower by 0.03-0.10). For an error analysis on data from both AP views, the mean absolute differences of observers' measurements were 1.1° to 1.8° for angles and 1.2 mm to 2.3 mm for distances. For the lateral cervical analysis, the observer error was in the interval 0.8° to 3.2° for angles and <1 mm for distances. Conclusions: The ICCs assuming random crossed factors understate reliability compared with previously published ICC results assuming nested factors. Reliability of the Harrison modified Risser-Ferguson method of line-drawing analysis on AP views is in the high range, with the majority of ICCs >0.88. For both the Harrison modified Risser-Ferguson method on AP views and posterior tangent method on lateral cervical views, the mean absolute differences of observers' measurements are small.

AN IMPROVED STRUCTURAL APPROACH FOR AUTOMATED RECOGNITION OF HANDPRINTED CHARACTERS

This paper examines several line-drawing pattern recognition methods for handwritten character recognition. They are the picture descriptive language (PDL), Berthod and Maroy (BM), extended Freeman's chain code (EFC), error transformation (ET), tree grammar (TG), and array grammar (AG) methods. A new character recognition scheme that uses improved extended octal codes as primitives is introduced. This scheme offers the advantages of handling flexible sizes, orientations, and variations, the need for fewer learning samples, and lower degree of ambiguity. Finally, the simulation of off-line character recognition by the real-time on-line counterpart is investigated.