Halftoning is a crucial part of image reproduction in print. First-order FM halftones, in which the single dots are stochastically distributed, is widely used in printing technologies, such as inkjet, that are able to stably print isolated dispersed dots. Printers, such as laser printers, that utilize electrophotographic technology are not able to stably print the isolated dots and therefore use clustered-dot halftones. Periodic clustered-dot, i.e. AM, halftones are commonly used in this type of printers but they suffer from undesired periodic interference pattern called moiré. An alternative solution is to use second-order FM halftones in which the clustered dots are stochastically distributed. The iterative halftoning techniques, that usually result in well-formed halftones, are operating on the whole input image and require extensive computations and thereby are very slow when the input image is large. In this paper, we introduce a method to generate image independent threshold matrices for first and second-order FM halftoning. The first-order threshold matrix generates well-formed halftone patterns and the second-order FM threshold matrix can be adjusted to produce clustered-dots of different size, shape and alignment. Using predetermined and image independent threshold matrices makes the proposed halftoning method a point-by-point process and thereby very fast.

This paper describes a method for 3-D surface estimation based on reflection measurements in different orientationsof the light source and the paper. To facilitate the estimation, surface facets that probably support specular reflection weremarked and isolated, so as to enable the application of sample Lambertian reflectance model over those non-specular reflectionpoints. A computer controlled imaging device was used to capture images in a large number of orientations. The image capturewas performed using several different exposures in order to present larger dynamic irradiance range. Images together with theircounterpoints under antithetical illuminations were used to deal with the possible situation that light failed illumination arrivalson some points locate behind bulges.Iteration using difference approximation as well as enforcing integrability algorithm wereused to calculate the surface height based on Shaping from Shading algorithm.

Gloss has a profound impact on the quality of printed matter. The manufacturing of the substrate and the printing process result in varying amount of gloss from the print. A glossy print with a smooth surface give a high degree of reflection in a relatively narrow specular sector. This contributes to the observed density range and is usually regarded as beneficial from a qualitative perspective. On surfaces that are less smooth, such as newsprint, the print quality is very dependent on the way gloss is angularly distributed. From the measurements it is clearly seen that gloss can be observed at different scales. The fibers themselves as well as the filler and surface material reflect with different characteristics.

This paper is based on 360 degree angular measurements with a geometry of 60 degree illumination and zero degree detector. The specimen is placed in the instrument on a moving stage. Mechanically moving the specimen relative to the light source and digitally restoring the geometry create an impression of a moving light-source. In this paper we will focus on the gloss measured on a very detailed level (micrometers) as points of high reflection.

The optical property of the substrate governs the reproduction characteristics and quality of printed paper. Paper is a very complex substrate that is designed for different application areas. In the simplest case it is a one-layer structure of fibers. In more complex structures the substrate may be build from several layers with different properties. In both situations it is vital to be able to control the manufacturing in order to achieve the desired product. This paper deals with simulation of differently composed structures that is difficult to accomplish in complex cases that goes beyond the Kubelka-Munk original theory. The paper describes qualitative results concerning the reproduction due to inhomogeneities in the layers themselves and the layer structures. More specifically we will study two simple structures, a one-layer substrate with inclusions ( for example recycled paper) and a two-layer substrate in which the coating layer thickness varies. In the second example the optical properties for the coating layer are supposed to be different from the base. The qualitative results show the degradations that can be expected due to inhomogeneities. The simulations will also allow for computation of the tone value increase in the simulated instances.

Distribution of ink jet ink in paper substrates and the consequences of ink penetration for printing color reproduction have been studied by combining microscopic image processing with spectroscopic analysis. The study focused on the effects of the composition of uncoated paper, for five laboratory papers plus two commercial products, all consisting of similar pulps but with different combinations of additives. In particular, it was observed that hydrophobizing internal size agents significantly reduced ink penetration, while their effect on paper optical properties was negligible. This observation thus made it possible to study experimentally the pure effects of ink penetration. Pairwise comparisons of prints on such laboratory papers with identical optical properties revealed remarkable impacts of ink penetration on optical density, causing color saturation reduction and color shift. These experimental observations confirmed the theoretical predictions.

A method combining microscopy with image analysis for studying ink penetration of ink-jet prints has been proposed. Prints on paper substrates of various material compositions have been microtomed, imaged with optical microscopy, and analyzed with image processing. The penetration depth and distribution of the ink-jet dye in the paper, which depend on the material compositions of the substrates and printed ink volumes, are then obtained by means of statistical analysis. The study focuses on uncoated fine papers, including five types of hand-sheets and two commercial papers. It is observed that ink penetration can be significantly reduced by adding internal sizing (hydrophobizing) chemicals in the hand-sheet making, while it is relatively less affected by addition of filler and fluorescent whitening agent (FWA). Ink volume obviously influences the depth of its penetration, with depth increasing linearly for higher ink volumes but displaying a disproportionately shallow penetration for smaller applied volumes.