Color image calibration is usually done with the aid of a color chart such as an X-Rite ColorChecker containing a set of carefully produced color patches. However, in many consumer applications, such as internet shopping, for which the correct reproduction of color can be very important, most users will not have a color chart readily available, and probably are not interested in purchasing one in any case given their relatively high cost. We propose using some readily available items that have relatively stable colors as a means of creating a simple color "chart." In particular, we explore the palette of colors created by the fleshy interior parts of oranges, lemons and limes, cooked egg white, and white sheets of paper. A sample of oranges, lemons, and limes from Canada, the United States, and Mexico has shown their color to be quite consistent, and therefore potentially suitable as a set of reference colors for color image calibration. Similarly, as sampling of typical white papers finds that although the whiteness varies, the average of several whites is quite stable. In the case of internet sales, a seller photographing color-sensitive merchandise, such as clothing, could simply include one or two of these items in each picture. This would provide an immediate point of reference for the purchaser as to whether or not the image colors are correct. Clearly, if the food colors and papers do not look right, neither will the merchandise when it is delivered.

Chocolate milk instability was monitored by time series of images. It is demonstrated how a time series of images can be summarized into a single image, named a stability barcode. The stability barcode is generated by collapsing time series frames to pixel columns and arranging the pixel columns to form the stability barcode. It is demonstrated how image filtering can be used in generation of different and more specific stability barcodes. Chocolate milk defects such as layers could be seen in barcodes generated using a median filter, curdling could be seen in barcodes generated using a standard deviation filter and marbling could be seen in barcodes made using an H-dome filter. Graphs for comparing the destabilization kinetics were deduced from the stability barcodes. The stability barcodes gave a visual summary of chocolate milk instability–the kinetic graphs a precise comparison of specific types of instability.

Industrial quality inspection using image analysis on astaxanthin coating in aquaculture feed pellets is of great importance for automatic production control. The pellets were divided into two groups: one with pellets coated using synthetic astaxanthin in fish oil and the other with pellets coated only with fish oil. In this study, multispectral image analysis of pellets captured reflection in 20 wavelengths (385–1050 nm). Linear discriminant analysis (LDA), principal component analysis, and support vector machine were used as statistical analysis. The features extracted from the multispectral images were pixel spectral values as well as using summary statistics such as the mean or median value of each pellet. Classification using LDA on pellet mean or median values showed overall good results. Multispectral imaging is a promising technique for noninvasive on-line quality food and feed products with optimal use of pigment and minimum amount of waste.

Quality control in the food industry is often performed by measuring various chemical compounds in the food involved. The authors propose an imaging concept for acquiring high-quality multispectral images to evaluate optical reflection changes in carrots and celeriac over a period of 14 days. For comparison, sensory analysis was performed on the same samples. Prior to multispectral image recording, the vegetables were prefried and frozen at –30° C for 4 months. During the 14 days of image recording, the vegetables were kept at +5° C. In this period, surface changes and thereby reflectance properties were very subtle. However, they noted statistically significant differences for some wavelengths and combinations of wavelengths. The corresponding sensory tests showed weak differences over the 14 days (significant at a 10% level of significance), which makes it the more important that the authors were able to detect minor changes using multispectral imaging. From our findings, it seems probable that oxidation caused the changes over time.

The poor performance of the MaxRGB illumination-estimation method is often used in the literature as a foil when promoting some new illumination-estimation method. However, MaxRGB has usually been tested on images of only 8-bits per channel, where clipping of high radiances is likely to have occurred. The question arises as to whether the method itself is inadequate, or rather whether it has simply been tested on data of inadequate dynamic range or with inadequate preprocessing. In particular, is MaxRGB's underlying assumption that there is a white or white-equivalent surface present in every scene too strong? This question is explored here in two ways. The first avenue of investigation is based on a new database of 105 sets of multiple-exposure images. High-dynamic range images are constructed from these sets as well. The color of the scene illumination is determined by taking an extra image of the scene containing four Gretag Macbeth mini-Colorcheckers placed at an angle to one another. MaxRGB is found to perform surprisingly well when tested on either the multiple-exposure or the high-dynamic range images. The second avenue of investigation is to add some simple preprocessing to the basic MaxRGB algorithm. By removing clipped pixels followed by median filtering, MaxRGB also performs better than previously reported when tested on test images of common color constancy test sets, specifically the Simon Fraser University 321-image indoor set. In particular, the Wilcoxon signed-rank test indicates that MaxRGB outperforms the most recent bright-pixel variant of color by correlation on the 321 set. MaxRGB is also competitive against the recent Edge-Based algorithm and significantly better than the computationally intensive Bayesian method on the Grayball set and the Colorchecker set. Overall, the results presented demonstrate that MaxRGB is far more effective than it has been reputed to be.

Print quality tests using off-the-shelf color electrophotographic printers revealed systematic tone fluctuations among the first several pages in print jobs after idle periods as short as 1 min, under certain environmental conditions. It can be shown that the tone values on the first few pages of a print job after 1 min of idle are statistically different from the tone values on the other pages of the same job. In the mid-tone ranges, the mean tone value difference between pages can differ by 4 ΔE₇₆ units under low temperature and low humidity conditions. This article presents an experimental approach to characterize this type of transient tone deviation in a print job for tone consistency control and improvement. A first-order difference model is employed to approximate the transient tone deviation. The resulting model can accurately predict the transient tone deviation over pages to within 1.3 ΔE₇₆ units, based on cross-validation.

In a single-layer organic photoreceptor, depletion charging and surface charge injection are important issues in the electrophotographic process. During the initial stages of the charging process, a finite amount of free and shallow trap generated charges are swept out of the bulk of the photoconductive layer. Also, surface charges from corona ions can be injected into the layer due to the adsorption of corona generated chemicals on the free surface. Such depletion charging and surface charge injection reduce the charge acceptance. In single-layer high gamma photoreceptors, the charge acceptance is not reduced in any degree in spite of abundant depletable carriers and excess surface charge injection. The photoinduced and dark discharge characteristics of such high gamma photoreceptors are found to be well described by a mathematical structural trap model which takes into account both carrier depletion and surface charge injection.