SYMLET AND GABOR WAVELET PREDICTION OF PRINT DEFECTS

Recent studies have been done to create models that predict the response of the human visual system (HVS) based on how the HVS processes an image. The most widely known of these models is the Gabor model, since the Gabor patterns closely resemble the receptive filters in the human eye. The work of this thesis examines the use of Symlets to represent the HVS, since Symlets provide the benefit of orthogonality. One major problem with Symlets is that the energy is not stable in respective Symlet channels when the image patterns are translated spatially. This thesis addresses this problem by up sampling Symlets instead of down sampling, and thus creating shift invariant Symlets. This thesis then compares the representation of Gabor versus Symlet approach in predicting the response of the HVS to detecting print defect patterns such as banding and graining. In summary we noticed that Symlet prediction outperforms the Gabor prediction thus Symlets would be a good choice for HVS response prediction. We also concluded that for banding defect periodicity and size are important factors that affect the response of the HVS to the patterns. For graining defects we noticed that size does not greatly affect the response of the HVS to the defect patterns. We introduced our results using two set of performance metrics, the mean and median

WAVELET AND SINE BASED ANALYSIS OF PRINT QUALITY EVALUATIONS

Recent advances in imaging technology have resulted in a proliferation of images across different media. Before it reaches the end user, these signals undergo several transformations, which may introduce defects/artifacts that affect the perceived image quality. In order to design and evaluate these imaging systems, perceived image quality must be measured. This work focuses on analysis of print image defects and characterization of printer artifacts such as banding and graininess by using a human visual system (HVS) based framework. Specifically the work addresses the prediction of visibility of print defects (banding and graininess) by representing the print defects in terms of the orthogonal wavelet and sinusoidal basis functions and combining the detection probabilities of each basis functions to predict the response of the human visual system (HVS). The detection probabilities for basis function components and the simulated print defects are obtained from separate subjective tests. The prediction performance from both the wavelet based and sine based approaches is compared with the subjective testing results .The wavelet based prediction performs better than the sinusoidal based approach and can be a useful technique in developing measures and methods for print quality evaluations based on HVS

Tent-pole spatial defect pooling for prediction of subjective quality assessment of streaks and bands in color printing

Abstract. An algorithm is described for measuring the subjective, visual impact of 1-D defects (streaks and bands

Measuring Visual Threshold of Inkjet Banding

Banding can be a major defect in inkjet printing. Knowing the visual sensitivity threshold of inkjet banding is therefore useful for understanding and pushing the technological limit of inkjet printing. There are many reports on the measurement of the human contrast sensitivity using self-luminous sinusoidal contrast targets. There are also reports on measuring the contrast sensitivity of sinusoidal banding on hardcopy targets. However, there has been no report on measuring visual threshold of banding defects that are characteristic of inkjet printing, which is usually not sinusoidal, despite the evidence that the visual threshold of a complex pattern may not be able to be predicted based on each of its harmonic components. In this paper, we report a study on measuring the human visual threshold of real-life inkjet banding defects. Inkjet banding samples were produced by simulating a type of actual inkjet print banding with a high quality proofing system. We simulated bandings at five different frequencies and various contrast levels and at a gray level corresponding to 25% pixel coverage. Fifty observers participated in a visibility and objectionability test with no restriction to view distances under normal office lighting condition and under special lighting for critical proofing viewing. The results obtained show lower threshold values in comparison to reported results on sinusoidal bandings