Abstract The authors have been attempting to digitize murals at the royal tomb of Amenophis III. When photographing the murals, two strobe lights, each of which had an umbrella, were used to provide uniform illumination. Nonetheless, the illumination was still somewhat non-uniform. This non-uniform illumination was corrected by applying an illumination model, which was evaluated using images of the simulated mural with and without white patches. The illumination model was then extended to two light sources and applied to images of the actual mural. The corrected images were observed to be more uniformly illuminated.

Abstract Some experimenters have begun to carry out image preference experiments over the web, with observers completing the task in their own time and using their own display devices. This reduces the administrative overhead, and opens the possibility to huge numbers of potential observers. However, we have to surrender some control over viewing conditions. In previous work, we evaluated an existing web-based paired comparison experiment against a lab-based counterpart and found that, generally, the two variants did not correlate to a significantly high degree. In this work we extend that study with the development of our own web-based research platform with greater control over viewing conditions and much larger quantities of observers (over 1,000, with more than 26,000 individual observations). With this, we show much more positive correlation between the web- and lab-based variants. We also show the similarity or otherwise between the two variants as a function of time, which reveals how many web-based observations are required to achieve stable results.

Abstract In this article, a local structure adaptive total variation (LSATV) method for image restoration is presented. In our method, a discontinuity indicator is first proposed based on the eigenvalues of the structure tensor, which can effectively distinguish between edges and noises. Based on the proposed discontinuity indicator, a p norm is adaptively selected to match the local structure property of a pixel. Therefore, the proposed LSATV method inherits the advantages of both the Tikhonov regularization method and the total variation regularization method. Experimental results show the robustness of the proposed method and its superiority to state-of-the-art methods.

Abstract The color of a print is affected by ink spreading and lateral light scattering in the substrate, making printed dots appear larger. Characterization of physical and optical dot gain is crucial for the graphic arts and paper industries. We propose a novel approach to separate physical from optical dot gain by use of a high-resolution camera. This approach is based on the histogram of microscale images captured by the camera. Having determined the actual physical dot shape, we estimate the modulation transfer function (MTF) of the paper substrate. The proposed method is validated by comparing the estimated MTF of 11 offset printed coated papers to the MTF obtained from the unprinted papers using measured and Monte Carlo simulated edge responses.

Abstract This article presents an approach to reduce the number of color patches printed during a calibration for electrophotography. During a calibration, primary color patches at different halftone levels are printed on a belt and are measured using on-board sensors. Regression models are used to predict primary color tone values on output media from these on-board sensor measurements. Then, the necessary adjustments using tone correction or other control variables are applied to compensate for tone deviation. Laying down and measuring color patches consumes time and toner. It is desired to reduce the number of calibration color patches while ensuring regression model accuracy. A procedure for color patch reduction is proposed in this work. In this procedure, a minimal set of color patches and their associated halftone levels are identified using variable selection algorithms. The results demonstrate that the minimal set contains 47.1% fewer calibration color patches than a full set, while the regression model accuracy of the minimal set is effectively the same as that of the full set.

Abstract The drop-on-demand inkjet is considered an important device for micro-electro-mechanical system production. Difficulties in understanding the fluid dynamic behavior of inks during drop ejection have led to the use of numerical simulations to predict drop formation. In this study, simulations were performed to predict and understand the jetting evolution of a nanocopper ink and a nanosilver ink. In order to predict the inkjettability of these inks, the Z number (the reciprocal of the Ohnesorge number) for different temperatures was determined. The results from the simulation studies were compared to experimental results obtained using a Dimatix inkjet printer.

Abstract A dual camera setup is proposed, consisting of a fixed (stationary) camera and a pan‐tilt‐zoom (PTZ) camera, employed in an automatic video surveillance system. The PTZ camera is zoomed in on a selected point in the fixed camera view and it may automatically track a moving object. For this purpose, two camera spatial calibration procedures are proposed. The PTZ camera is calibrated in relation to the fixed camera image, using interpolated look-up tables for pan and tilt values. For the calibration of the fixed camera, an extension of the Tsai algorithm is proposed, based only on measurements of distances between calibration points. This procedure reduces the time needed to obtain the calibration set and improves calibration accuracy. An algorithm for calculating PTZ values required for tracking of a moving object with the PTZ camera is also presented. The performance of the proposed algorithms is evaluated using the measured data.