Efficient Color Constancy with Local Surface Reflectance Statistics

2014 ◽  
pp. 158-173 ◽  
Author(s):  
Shaobing Gao ◽  
Wangwang Han ◽  
Kaifu Yang ◽  
Chaoyi Li ◽  
Yongjie Li
Keyword(s):  
Color Constancy ◽  
Surface Reflectance ◽  
Local Surface

Conversion of the Retinal Image Using Gray World Technique

2018 ◽  
Vol 36 ◽  
pp. 70-77 ◽  
Author(s):  
Wan Azani Mustafa ◽  
Haniza Yazid
Keyword(s):  
Retinal Image ◽  
Signal To Noise Ratio ◽  
Color Constancy ◽  
Main Idea ◽  
Retinal Images ◽  
Surface Reflectance ◽  
Contrast Variation ◽  
Region Data ◽  
Timely Treatment

Retinal images are routinely acquired and assessed to provide diagnostic for many important diseases like diabetic retinopathy. People with proliferative retinopathy can reduce their risk of blindness by 95 percent with timely treatment and appropriate follow-up care. The color constancy is used in this context to define the ability of the visual system to estimate an object color transmitting an unpredictable spectrum to the eyes. In this paper, a Gray World method was proposed by assuming the average of the surface reflectance of a typical scene is some pre-specified value. The main idea based on illumination estimated using the statistical region data. The effectiveness of the Gray Word method and normal gray technique was calculated by using Mean Square Error (MSE) and Peak Signal to Noise Ratio (PSNR). The Gray World achieved the highest PSNR and lowest MSE proved that the image quality was improved. The proposed method can be used to help the ophthalmologist to detect a lesion in the retinal image automatically. Through the contrast variation in retinal images, the disease can be recognized very well.

scholarly journals Protanopic observers show nearly normal color constancy with natural reflectance spectra

2004 ◽  
Vol 21 (3) ◽  
pp. 347-351 ◽  
Author(s):  
RIGMOR C. BARAAS ◽  
DAVID H. FOSTER ◽  
KINJIRO AMANO ◽  
SÉRGIO M.C. NASCIMENTO
Keyword(s):  
Spatial Structure ◽  
Natural Environment ◽  
Color Constancy ◽  
Reflectance Spectra ◽  
Surface Reflectance ◽  
Color Monitor ◽  
Computer Controlled

The ability of color-deficient observers to discriminate between illuminant changes and surface-reflectance changes in a scene was tested with natural and Munsell reflectance spectra. To avoid the confounding effects of spatial structure, stimuli were simulations of Mondrian-like colored patterns, presented on a computer-controlled color monitor. Protanopes performed less well than normal trichromats, regardless of the type of reflectance spectra, but they were least disadvantaged with patterns comprising reflectance spectra drawn from urban and rural scenes, more characteristic of the natural environment.

scholarly journals Master thesis: Extensions of a linear model of surface reflectance

2019 ◽  
Author(s):  
Alban Flachot
Keyword(s):  
Linear Model ◽  
Linear Transformation ◽  
Color Constancy ◽  
Three Dimensional ◽  
Linear Operators ◽  
Surface Reflectance ◽  
Geometrical Properties ◽  
Common Basis ◽  
Reflected Light ◽  
Human Color Vision

Philipona O’Regan recently proposed a linear model of surface reflectance asit is sensed by the human eyes. In their model, the three dimensional cone response to reflected light is accurately approximated by a linear transformation of the three dimensional response to illumination. The geometrical properties of this linear transformation, such as singularity, correlate with psychophysical results on focal colors and unique hues. Later, Vazquez-Corral et al. built a bridge between Philipona & O’Regan’s model and von Kries-like approaches to color constancy in computer vision by showing that the linear operators could be diagonalized in a common basis. However both of these studies required specifyinga particular dataset of illuminants. We will show in this paper that it is possible to compute adequate linear operators and a common basis for diagonalization without specifying any particular set of illuminants, thus enhancing their generalizability to illuminant changes, while maintaining correlations with features of the human color vision. Further analysis of the characteristics of singularity in reflection properties will also be presented.

Pictorial Reliefs as Organized Local Surface Shapes

2013 ◽  
Author(s):  
Johan Wagemans ◽  
Andrea Van Doorn ◽  
Jan Koenderink
Keyword(s):  
Local Surface

BOREAS RSS-01 PARABOLA SSA SURFACE REFLECTANCE AND TRANSMITTANCE DATA

1999 ◽  
Author(s):  
S. P. AHMAD ◽  
D. W. DEERING ◽  
T. F. ECK ◽  
E. M. MIDDLETON
Keyword(s):  
Surface Reflectance

A Flying Gray Ball Multi-illuminant Image Dataset for Color Research

2020 ◽  
Vol 64 (5) ◽  
pp. 50411-1-50411-8
Author(s):  
Hoda Aghaei ◽  
Brian Funt
Keyword(s):  
Machine Vision ◽  
Spectral Reflectance ◽  
Color Constancy ◽  
Ground Truth ◽  
Practical Approach ◽  
Post Processing ◽  
Illumination Estimation ◽  
Processing Step ◽  
Image Dataset

Abstract For research in the field of illumination estimation and color constancy, there is a need for ground-truth measurement of the illumination color at many locations within multi-illuminant scenes. A practical approach to obtaining such ground-truth illumination data is presented here. The proposed method involves using a drone to carry a gray ball of known percent surface spectral reflectance throughout a scene while photographing it frequently during the flight using a calibrated camera. The captured images are then post-processed. In the post-processing step, machine vision techniques are used to detect the gray ball within each frame. The camera RGB of light reflected from the gray ball provides a measure of the illumination color at that location. In total, the dataset contains 30 scenes with 100 illumination measurements on average per scene. The dataset is available for download free of charge.

PEMETAAN SEBARAN PADANG LAMUN MENGGUNAKAN CITRA SATELIT LANDSAT 8 DI KEPULAUAN TANIMBAR KABUPATEN MALUKU TENGGARA BARAT PROVINSI MALUKU

2019 ◽  
Vol 3 ◽  
pp. 871
Author(s):  
Desita Anggraeni ◽  
M. Nurkholis Fauzi ◽  
Christian Novia Ngesti H.
Keyword(s):  
Landsat 8 ◽  
Surface Reflectance ◽  
Halophila Ovalis ◽  
Halodule Uninervis ◽  
Gap Data

Padang lamun merupakan habitat penting pesisir yang memiliki peran kunci dalam ekosistem pesisir. Kawasan ini merupakan area asuhan bagi ikan-ikan kecil, udang, persembunyian biota dari predatornya, pendaur zat hara, serta penyerap nutrien dari limpasan air laut yang dapat membantu menstabilkan sedimen dan kejernihan air. Kepulauan Tanimbar merupakan salah satu lokasi di Provinsi Maluku dengan potensi sebaran lamun yang cukup luas, namun informasi mengenai sebaran lamun di kawasan ini tidak terdata dengan baik. Teknologi penginderaan jauh merupakan salah satu alternatif untuk mengisi gap data di area yang luas dan sulit dijangkau, termasuk untuk memetakan sebaran lamun di Kepulauan Tanimbar. Penelitian ini bertujuan untuk menyediakan data dasar sebaran dan luas habitat lamun di pesisir Kepulauan Tanimbar. Metode yang digunakan adalah analisis citra penginderaan jauh Landsat 8, menerapkan penajaman citra untuk perairan dangkal menggunakan algoritma Lyzenga. Citra Landsat yang digunakan Landsat Surface Reflectance liputan path/row 106/65 dan 106/66 tahun perekaman 2017. Pengambilan data lapangan dilakukan pada tanggal 1-10 November 2017. Metode pengambilan data lamun dilakukan menggunakan metode seagrass watch . Hasil pengolahan citra menunjukkan lamun terdistribusi merata di seluruh pesisir Kepulauan Tanimbar dengan luas total 5.615,63 hektar dengan tutupan terpadat di sekitar Pulau Seira. Hasil survei lapangan menunjukkan tutupan lamun terpadat dijumpai di Formusan dengan tutupan lamun rata-rata 95%. Kondisi lamun paling baik berada di daerah Sabal, didukung kondisi air yang sangat jernih dengan substrat utama pasir. Berdasarkan hasil pengamatan lapangan, jenis lamun yang ditemukan antara lain: E n h alu s a c o r oid e s , T h ala s sia h e m p ric hii, C y m o d o c e a s e r r ula t a , C y m o d o c e a rotundata, Syringodi um isoetifolium, Halodule uninervis, Halophila ovalis, dan Halophila minor .

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