Derivation and modelling hue uniformity and development of the IPT color space

Metric color spaces have been determined to be significantly non-uniform in the hue attribute of color appearance. Several independent sources have confirmed the non-uniformity. A data set was obtained during the course of this thesis work that contains the largest sampling of color space to date which can be used to compare models of color appearance. The data set obtained was compared to existing data sets and found to correspond closely. Lookup table methods were employed to test significant differences between data sets. A simple modeling approach was taken based on commonly understood color space models and knowledge of the visual system. Several color spaces can be derived using the simple model, and one was chosen that models hue uniformity very well and has other desirable attributes. This new color space is named IPT. Many visual data sets were plotted in the IPT color space and all show improved performance over industry standard color spaces. The IPT color space has applications in color data representation, gamut mapping, and color appearance modeling

OBJECT MATCHING IN DISJOINT CAMERAS USING A COLOR TRANSFER APPROACH

Object appearance models are a consequence of illumination, viewing direction, camera intrinsics, and other conditions that are specific to a particular camera. As a result, a model acquired in one view is often inappropriate for use in other viewpoints. In this work we treat this appearance model distortion between two non-overlapping cameras as one in which some unknown color transfer function warps a known appearance model from one view to another. We demonstrate how to recover this function in the case where the distortion function is approximated as general affine and object appearance is represented as a mixture of Gaussians. Appearance models are brought into correspondence by searching for a bijection function that best minimizes an entropic metric for model dissimilarity. These correspondences lead to a solution for the transfer function that brings the parameters of the models into alignment in the UV chromaticity plane. Finally, a set of these transfer functions acquired from a collection of object pairs are generalized to a single camera-pair-specific transfer function via robust fitting. We demonstrate the method in the context of a video surveillance network and show that recognition of subjects in disjoint views can be significantly improved using the new color transfer approach

Uniform color space analysis of LACIE image products

The author has identified the following significant results. Analysis and comparison of image products generated by different algorithms show that the scaling and biasing of data channels for control of PFC primaries lead to loss of information (in a probability-of misclassification sense) by two major processes. In order of importance they are: neglecting the input of one channel of data in any one image, and failing to provide sufficient color resolution of the data. The scaling and biasing approach tends to distort distance relationships in data space and provides less than desirable resolution when the data variation is typical of a developed, nonhazy agricultural scene

A Study of Colour Rendering in the In-Camera Imaging Pipeline

Consumer cameras such as digital single-lens reflex camera (DSLR) and smartphone cameras have onboard hardware that applies a series of processing steps to transform the initial captured raw sensor image to the final output image that is provided to the user. These processing steps collectively make up the in-camera image processing pipeline. This dissertation aims to study the processing steps related to colour rendering which can be categorized into two stages. The first stage is to convert an image's sensor-specific raw colour space to a device-independent perceptual colour space. The second stage is to further process the image into a display-referred colour space and includes photo-finishing routines to make the image appear visually pleasing to a human. This dissertation makes four contributions towards the study of camera colour rendering. The first contribution is the development of a software-based research platform that closely emulates the in-camera image processing pipeline hardware. This platform allows the examination of the various image states of the captured image as it is processed from the sensor response to the final display output. Our second contribution is to demonstrate the advantage of having access to intermediate image states within the in-camera pipeline that provide more accurate colourimetric consistency among multiple cameras. Our third contribution is to analyze the current colourimetric method used by consumer cameras and to propose a modification that is able to improve its colour accuracy. Our fourth contribution is to describe how to customize a camera imaging pipeline using machine vision cameras to produce high-quality perceptual images for dermatological applications. The dissertation concludes with a summary and future directions

Calm Displays and Their Applications : Making Emissive Displays Mimic Reflective Surfaces Using Visual Psychophysics, Light Sensing and Colour Science

Ph. D. Thesis.Our environment is increasingly full of obtrusive display panels, which become illuminating surfaces when on, and void black rectangles when off. Some researchers argue that emissive displays are incompatible with Weiser and Seely Brown's vision of "calm technology", due to their inability to seamlessly blend into the background. Indeed, Mankoff has shown that for any ambient technology, the ability to move into the periphery is the most relevant factor in their usability. In this thesis, a background mode for displays is proposed based on the idea that displays can look like an ordinary piece of reflective paper showing the same content. The thesis consists of three main parts. In the first part (Chapter 4), human colour matching performance between an emissive display and reflective paper under chromatic lighting conditions is measured in a psychophysical experiment. We find that threshold discrimination ellipses vary with condition (16.0×6.0 ΔEab on average), with lower sensitivity to chroma than hue changes. Match distributions are bimodal for some conditions. In the second part (Chapter 5), an algorithm enabling emissive displays to look like reflective paper is described and evaluated, giving an average error of ΔEab = 10.2 between display and paper. A field study showed that paper-like displays are more acceptable in bedrooms and that people are more likely to keep them always on than normal displays. Finally, the third part (Chapter 6) concerns the development and four-week trial of a paper-like display application. Using the autobiographical design method, a system for sharing bedtime with a remote partner was developed. We see that once unobtrusive, display systems are desired for use even in spaces like bedrooms. Paper-like displays enable both emerging and existing devices to move into the periphery and become “invisible”, and therefore provide a new building block of calm technology that is not achievable using simple emissive displays

COLOR MAPPING FOR CAMERA-BASED COLOR CALIBRATION AND COLOR TRANSFER

Ph.DDOCTOR OF PHILOSOPH

Characterisation of a multispectral digital camera System for quantitatively comparing complex animal Patterns in natural environments.

Animal coloration can be described by complex colour patterns including elements of varying size, shape and spectral profile which commonly reflect energy outside the spectral range visible for humans. Whilst spectrometry is currently employed for the quantitative study of animal coloration, it is limited on its ability to describe the spatial characteristics of spectral differences in patterns. Digital photography has recently been used as a tool for measuring spatial and spectral properties of patterns based on quantitative analysis of linear camera responses recovered after characterising the device. However current applications of digital imaging for studying animal coloration are limited to image recording within a laboratory environment considering controlled lighting conditions. Here a refined methodology for camera characterisation is developed permitting the recording of images under different illumination conditions typical of natural environments. The characterised camera system thus allows recording images from reflected ultraviolet and visible radiation resulting in a multispectral digital camera system. Furthermore a standardised imaging processing workflow was developed based on specific characteristics of the camera thus making possible an objective comparison from images. An application of the characterised camera system is exemplified in the study of animal colour patterns adapted for camouflage using as a model two Australian, endemic lizard species. The interaction between the spectral and spatial properties of the respective lizards produces complex patterns than cannot be interpreted by spectrophotometry alone. Data obtained from analysis of images recorded with the characterised camera system in the visible and near-ultraviolet region of the spectrum reveal significative differences between sex and species and a possible interaction between sex and species, suggesting microhabitat specialisation to different backgrounds

Semantik renk değişmezliği

Color constancy aims to perceive the actual color of an object, disregarding the effectof the light source. Recent works showed that utilizing the semantic information inan image enhances the performance of the computational color constancy methods.Considering the recent success of the segmentation methods and the increased numberof labeled images, we propose a color constancy method that combines individualilluminant estimations of detected objects which are computed using the classes of theobjects and their associated colors. Then we introduce a weighting system that valuesthe applicability of the object classes to the color constancy problem. Lastly, weintroduce another metric expressing the detected object and how well it fits the learnedmodel of its class. Finally, we evaluate our proposed method on a popular colorconstancy dataset, confirming that each weight addition enhances the performanceof the global illuminant estimation. Experimental results show promising results,outperforming the conventional methods while competing with the state of the artmethods.--M.S. - Master of Scienc