Color homography

We show the surprising result that colors across a change in viewing condition (changing light color, shading and camera) are related by a homography. Our homography color correction application delivers improved color fidelity compared with the linear least-square.Comment: Accepted by Progress in Colour Studies 201

EverFarm® - Climate adapted perennial-based farming systems for dryland agriculture in southern Australia

AbstractAustralian dryland agriculture will be affected by climate change in a number of ways. First, higher temperatures and changes to rainfall are likely to create greater variability of crop yields and livestock productivity. Second, government policies introduced to mitigate greenhouse gas emissions are likely to influence production costs and commodity prices. Third, global trade patterns are likely to alter as populations increase, and as climate change continues to affect producers and consumers worldwide. This will create both challenges and opportunities for Australian agriculture.Farmers will have to respond to the additional challenge of climate change even when it is compounded by existing long term stresses associated with declining terms of trade, climate variability and existing environmental issues. Investing in new land-use options to combat climate change, with their associated risks, is made more difficult by being set against a backdrop of declining profitability. The opportunity to create transformational change in farming enterprises was tested by combining the multiple components of the potential future perennial‐based dryland farming systems and assessing their expected contribution to climate change adaptation. This project has found that adopting perennial pastures for livestock grazing and tree crops for biomass production, when planted on appropriate soils, can improve profitability when compared to the existing land uses facing a changing climate.  In some farming systems increased cropping is likely to result in improved future farm profits.This work demonstrated that Mallees as a biomass tree crop can be cohesively integrated into existing farming systems with minimal interruption to normal operations of livestock and cropping enterprises. A woody biomass crop can be profitable and diversify revenue risk by enabling farmers to supply biomass and sequester carbon to relevant markets. This work demonstrates suitable designs of a mallee belt planting layout that minimizes costs and maximizes benefits when planted in appropriate agro‐climatic zones and where there are adequate soil conditions. Knowledge developed from this work will help build farmers capacity about climate change adaptation and assist in achieving positive social, environmental and economic outcomes.Please cite this report as:Farquharson, R, Abadi, A, Finlayson, J, Ramilan, T,  Liu, DL, Muhaddin, A, Clark, S, Robertson, S, Mendham, D, Thomas, Q,  McGrath, J 2013 EverFarm® – Climate adapted perennial-based farming systems for dryland agriculture in southern Australia, National Climate Change Adaptation Research Facility, Gold Coast, pp. 159.AbstractAustralian dryland agriculture will be affected by climate change in a number of ways. First, higher temperatures and changes to rainfall are likely to create greater variability of crop yields and livestock productivity. Second, government policies introduced to mitigate greenhouse gas emissions are likely to influence production costs and commodity prices. Third, global trade patterns are likely to alter as populations increase, and as climate change continues to affect producers and consumers worldwide. This will create both challenges and opportunities for Australian agriculture.Farmers will have to respond to the additional challenge of climate change even when it is compounded by existing long term stresses associated with declining terms of trade, climate variability and existing environmental issues. Investing in new land-use options to combat climate change, with their associated risks, is made more difficult by being set against a backdrop of declining profitability. The opportunity to create transformational change in farming enterprises was tested by combining the multiple components of the potential future perennial‐based dryland farming systems and assessing their expected contribution to climate change adaptation. This project has found that adopting perennial pastures for livestock grazing and tree crops for biomass production, when planted on appropriate soils, can improve profitability when compared to the existing land uses facing a changing climate.  In some farming systems increased cropping is likely to result in improved future farm profits.This work demonstrated that Mallees as a biomass tree crop can be cohesively integrated into existing farming systems with minimal interruption to normal operations of livestock and cropping enterprises. A woody biomass crop can be profitable and diversify revenue risk by enabling farmers to supply biomass and sequester carbon to relevant markets. This work demonstrates suitable designs of a mallee belt planting layout that minimizes costs and maximizes benefits when planted in appropriate agro‐climatic zones and where there are adequate soil conditions. Knowledge developed from this work will help build farmers capacity about climate change adaptation and assist in achieving positive social, environmental and economic outcomes

Recoding Color Transfer as A Color Homography

Color transfer is an image editing process that adjusts the colors of a picture to match a target picture's color theme. A natural color transfer not only matches the color styles but also prevents after-transfer artifacts due to image compression, noise, and gradient smoothness change. The recently discovered color homography theorem proves that colors across a change in photometric viewing condition are related by a homography. In this paper, we propose a color-homography-based color transfer decomposition which encodes color transfer as a combination of chromaticity shift and shading adjustment. A powerful form of shading adjustment is shown to be a global shading curve by which the same shading homography can be applied elsewhere. Our experiments show that the proposed color transfer decomposition provides a very close approximation to many popular color transfer methods. The advantage of our approach is that the learned color transfer can be applied to many other images (e.g. other frames in a video), instead of a frame-to-frame basis. We demonstrate two applications for color transfer enhancement and video color grading re-application. This simple model of color transfer is also important for future color transfer algorithm design

Color Homography: theory and applications

Images of co-planar points in 3-dimensional space taken from different camera positions are a homography apart. Homographies are at the heart of geometric methods in computer vision and are used in geometric camera calibration, 3D reconstruction, stereo vision and image mosaicking among other tasks. In this paper we show the surprising result that homographies are the apposite tool for relating image colors of the same scene when the capture conditions -- illumination color, shading and device -- change. Three applications of color homographies are investigated. First, we show that color calibration is correctly formulated as a homography problem. Second, we compare the chromaticity distributions of an image of colorful objects to a database of object chromaticity distributions using homography matching. In the color transfer problem, the colors in one image are mapped so that the resulting image color style matches that of a target image. We show that natural image color transfer can be re-interpreted as a color homography mapping. Experiments demonstrate that solving the color homography problem leads to more accurate calibration, improved color-based object recognition, and we present a new direction for developing natural color transfer algorithms

Color Homography Color Correction

Homographies -- a mathematical formalism for relating image points across different camera viewpoints -- are at the foundations of geometric methods in computer vision and are used in geometric camera calibration, image registration, and stereo vision and other tasks. In this paper, we show the surprising result that colors across a change in viewing condition (changing light color, shading and camera) are also related by a homography. We propose a new color correction method based on color homography. Experiments demonstrate that solving the color homography problem leads to more accurate calibration

Rank-Based Radiometric Calibration

Raw images are more useful than JPEG images for machine vision algorithms and professional photographers because raw images preserve a linear relation between pixel values and the light measured from the scene. A camera is radiometrically calibrated if there is a computational model which can predict how the raw image is mapped to the corresponding rendered image (e.g. JPEGs) and vice versa. Our method makes use of the observation that the rank order of pixel values are mostly preserved post color correction. We show that this observation is the key for getting a compact and robust radiometric calibration model. Since our method requires fewer variables, it can be solved for using less calibration data. An additional advantage is that we can derive the camera pipeline from a single pair of raw-JPEG images. Experiments demonstrate that our method delivers state-of-the-art results (especially for the most interesting conversion from JPEG to raw)

Combined fluorescence lifetime and surface topographical imaging of biological tissue

In this work a combined fluorescence lifetime and surface topographical imaging system is demonstrated. Based around a 126 × 192 time resolved single photon avalanche diode (SPAD) array operating in time correlated single-photon counting (TCSPC) mode, both the fluorescence lifetime and time of flight (ToF) can be calculated on a pixel by pixel basis. Initial tests on fluorescent samples show it is able to provide 4 mm resolution in distance and 0.4 ns resolution in lifetime. This combined modality has potential biomedical applications such as surgical guidance, endoscopy and diagnostic imaging. The system is demonstrated on both ovine and human pulmonary tissue samples, where it offers excellent fluorescence lifetime contrast whilst also giving a measure of the distance to the sample surfac