Color Interpolation Algorithm Research Articles

An improved hibbard interpolation algorithm based on edge gradient feature detection using Sobel operator

Color interpolation algorithms have important applications in color image processing, and many interpolation algorithms have been proposed one after another. The bilinear interpolation algorithm, Cok interpolation algorithm and gradient edge interpolation are three classical interpolation algorithms, however, they may cause problems such as zipper effect and Mohr's stripe effect. In this paper, this paper optimize the gradient edge algorithm, calculate the gradient by using Sobel operator and fit the direction of the edge in a weighted way, and propose a gradient edge weighted interpolation algorithm based on Sobel operator to improve the performance of the interpolation algorithm. Through the validation of color image recovery, the results show that the subjective visual effect and objective evaluation indexes such as structural similarity index, peak signal-to-noise ratio and minimum mean square error of the improved algorithm proposed in this paper are better than the traditional algorithm, which is of great significance to the improvement of the interpolation algorithm.

Analysis and Comparison of Three Classical Color Image Interpolation Algorithms

With the development of society, the progress of science and technology, the level of computer has been improved. Digital imaging technology has also achieved unprecedented development. The most commonly used digital cameras are Charge-coupled device (CCD) and Complementary Metal Oxide Semiconductor (CMOS) image sensors. Bayer filters are often used to help sensors capture color information. However, only one component can be achieved per pixel. Full-color images must be obtained by color interpolation. Therefore, the color interpolation algorithm has attracted the attention of the academic community. In this paper, three classical color interpolation algorithms- Bilinear interpolation algorithm, COK Algorithm, Gradient Interpolation Algorithm- are compared and studied. The Optimal Algorithm is selected by comparing false color, noise and color moire fringe. After comparison, it is found that the three basic algorithms will have color moire fringes appear. But the gradient interpolation algorithm has the least moire fringe and noise. COK Algorithm, second of all. But the COK Algorithm has color overflows.

FPGA Acceleration of Color Interpolation Algorithm Based on Gradient and Color Difference

To quickly and efficiently achieve a high-quality color image on the embedded platform, designed and used FPGA to complete Bayer pattern image Color interpolation. In this paper, we proposed a color interpolation algorithm based on image gradient direction and color difference. The algorithm calculates the G component according to the gradient value and color difference at the pixel to be interpolated, and then calculates the missing R component and B component based on the G component interpolation. Finally, the pixels of the image boundary area are interpolated. Tested on the Kodak dataset, the experimental results show that the subjective visual quality and objective image quality evaluation of the algorithm is superior to the conventional algorithm. On the other hand, and reduce problems such as image aliasing and edge blurring. The proposed algorithm has been applied to the actual Xilinx’s FPGA platform, a real-time speed of 120 MHz, enabling real-time image color Interpolation.

ES-COINA: A novel energy scalable quality-aware color interpolation architecture

Energy-efficiency is the critical requirement for the battery operated portable devices exhibiting compute-intensive image/video processing applications. The color interpolation is the most energy consuming operation used within these devices to reconstruct the full resolution color image. In this paper, three approximate color interpolation architectures are proposed by exploiting the relative significance of the computations. These architectures provide high energy efficiency at the cost of small degradation in quality. Further, novel energy scalable color interpolation algorithm and its architecture (ES-COINA) are proposed that provide improved quality-energy trade-off. The efficacy of the proposed architectures is evaluated using various quality metrics by simulating them with different benchmark images from Kodak dataset. The proposed architectures are implemented on Artix-7 FPGA board and compared over the existing. Further, the proposed and existing architectures are implemented on Cadence RTL Compiler and synthesized with 180nm technology file. The simulation results show that the proposed approximate architectures provide 88%, 71.3%, and 46% reduced energy consumption over the best-known color interpolation architecture with a little degradation in quality. Further, the proposed ES-COINA reduces the energy consumption by 21% which can be extended to 92.6% when switched from high quality to high energy-efficient mode of operation.

확장된 색차 그라디언트에 기반한 컬러 보간 알고리즘

확장된 색차 그라디언트에 기반한 컬러 보간 알고리즘

Quality Evaluation of Chromatic Interpolation Algorithms for Image Acquisition System

The main goal of the Libertad 2 mission is to take images of the Earth’s surface in the visible spectrum with a multispectral sensor and send them as a Bayer array. To carry out the reconstruction in land of these images and to view them in a RGB color model, it is necessary to use a color interpolation algorithm to determine the values of the different channels of color in each pixel. This document presents an analysis of five chromatic interpolation algorithms (Nearest Neighbor, Adaptive Color Plane, Bilinear, Smooth Hue Transition and Median Based). The analysis also includes the identification of image evaluation algorithms without reference and the artifacts (False Color Measure, Blur Metric and Chromatic and Achromatic Zipper). Finally, the analysis results of the chromatic interpolation algorithms and the selection of the most suitable algorithm for the Libertad 2 satellite mission data are presented.

Erratum to: Color interpolation algorithm for an RWB color filter array including double-exposed white channel

Erratum to: Color interpolation algorithm for an RWB color filter array including double-exposed white channel

Color interpolation algorithm for an RWB color filter array including double-exposed white channel

In this paper, we propose a color interpolation algorithm for a red-white-blue (RWB) color filter array (CFA) that uses a double exposed white channel instead of a single exposed green (G) channel. The double-exposed RWB CFA pattern, which captures two white channels at different exposure times simultaneously, improves the sensitivity and provides a solution for the rapid saturation problem of W channel although spatial resolution is degraded due to the lack of a suitable color interpolation algorithm. The proposed algorithm is designed and optimized for the double-exposed RWB CFA pattern. Two white channels are interpolated by using directional color difference information. The red and blue channels are interpolated by applying a guided filter that uses the interpolated white channel as a guided value. The proposed method resolves spatial resolution degradation, particularly in the horizontal direction, which is a challenging problem in the double-exposed RWB CFA pattern. Experimental results demonstrate that the proposed algorithm outperforms other color interpolation methods in terms of both objective and subjective criteria.

VLSI Implementation of an Adaptive Edge-Enhanced Color Interpolation Processor for Real-Time Video Applications

In this paper, a low-complexity color interpolation algorithm is proposed for the very-large-scale integration (VLSI) implementation in real-time applications. The proposed novel algorithm consists of an edge detector, an anisotropic weighting model, and a filter-based compensator. The anisotropic weighting model is designed to catch more information in horizontal than vertical directions. The filter-based compensation methodology includes a Laplacian and spatial sharpening filters, which are developed to improve the edge information and reduce the blurring effect. In addition, the hardware cost was successfully reduced by hardware sharing and reconfigurable design techniques. The VLSI architecture of the proposed design achieves 200 MHz with 5.2-K gate counts, and its core area is 64 236 μm2 synthesized by a 0.18-μm CMOS process. Compared with the previous low-complexity techniques, this paper not only reduces gate counts or power consumption by more than 8% or 91.7%, respectively, but also improves the average color peak signal-to-noise ratio quality by more than 1.6 dB.

Image Quality Evaluation on Modified Bayer CFA

Almost all digital cameras adopt a color filter array to acquire images and requesting a demosaicking process of the sub-sampled color components to have the full color image. Thus, it is necessary to restore the CFA image correctly. Otherwise, perceptible color errors are presented. This paper proposes a color interpolation algorithm based on filter. The CFA we used is modified Bayer CFA. Simulation results show that the proposed method is effective and yield high performance in CPSNR and S-CIELAB.

A no-reference metric for demosaicing artifacts that fits psycho-visual experiments

The present work concerns the analysis of how demosaicing artifacts affect image quality and proposes a novel no-reference metric for their quantification. This metric that fits the psycho-visual data obtained by an experiment analyzes the perceived distortions produced by demosaicing algorithms. The demosaicing operation consists of a combination of color interpolation (CI) and anti-aliasing (AA) algorithms and converts a raw image acquired with a single sensor array, overlaid with a color filter array, into a full-color image. The most prominent artifact generated by demosaicing algorithms is called zipper. The zipper artifact is characterized by segments (zips) with an On–Off pattern. We perform psycho-visual experiments on a dataset of images that covers nine different degrees of distortions, obtained using three CI algorithms combined with two AA algorithms. We then propose our no-reference metric based on measures of blurriness, chromatic and achromatic distortions to fit the psycho-visual data. With this metric demosaicing algorithms could be evaluated and compared.

방향성 필터를 이용하여 대각선 에지를 고려한 Demosaicing 알고리즘 및 하드웨어 구현

대부분의 디지털 촬영 장치는 비용 및 속도 상의 이점을 위해 Color Filter Array(CFA)를 포함하고 있는 단일 이미지 센서를 사용한다. 따라서 완전한 컬러 영상으로 복원하기 위하여 다양한 컬러 보간 방법이 개발되고 있다. 본 논문은 이러한 컬러 보간 방법 중, 방향성 필터를 이용하여 수직, 수평, 대각선 방향의 에지를 고려한 컬러 보간 방법에 관한 것이다. 하드웨어 구현을 위해 하드웨어 자원의 효율성을 고려하였다. Kodak 테스트 영상 24장으로 실험하여 기존 방법과 비교함으로써 제안한 방법의 성능을 확인하였다. Verilog HDL로 구현하였으며, Virtex4 FPGA 보드와 CMOS 이미지 센서를 이용하여 검증하였다. Most digital cameras use a single image sensor with Color Filter Array(CFA) for the advantage of costs and speed. The various color interpolation(demosaicing) algorithms are researched to reconstruct a full representation of the image. In this paper, we proposed a method of demosaicing about using weighted directional filter for vertical, horizontal, and diagonal direction edge. The method considered the efficiency of hardware resources for hardware implementation. The performance of proposed method was confirmed by comparing the conventional method in experiments using 24 Kodak test images. The proposed method was designed by Verilog HDL and was verified by using Virtex4 FPGA boards and CMOS Image Sensor.

集成数字图像处理的低功耗1/8英寸CMOS视觉传感器

A digital still camera image processing system on a chip, different from the video camera system, is presented for mobile phone to reduce the power consumption and size. A new color interpolation algorithm is proposed to enhance the image quality. The system can also process fixed patten noise (FPN) reduction, color correction, gamma correction, RGB/YUV space transfer, etc. The chip is controlled by sensor registers by inter-integrated circuit (I2C) interface. The voltage for both the front-end analog and the pad circuits is 2.8 V, and the volatge for the image signal processing is 1.8 V. The chip running under the external 13.5-MHz clock has a video data rate of 30 frames/s and the measured power dissipation is about 75 mW.

Color interpolation with variable color ratio considering cross-channel correlation

A color interpolation algorithm is necessary to acquire color images of good quality with a digital still camera in which a single CCD image sensor is equiped. Since a color filter array is adopted, we must interpolate missing color values in the red, green, and blue channels at each pixel location. Inappropriate color interpolation causes color arti- facts, resulting in degraded color resolution. A color interpolation algo- rithm with a variable color ratio is proposed by incorporating cross- channel correlation. The color ratio of weighted sums in the color channels is utilized instead of the weighted sum of color ratios, and the color ratio varies with respect to the cross-channel correlation at each pixel. The proposed algorithm is composed of initial color interpolation step and the updating step of the green channel, where the updating step is carried out iteratively. Furthermore, a minus weighted sum based on the external divide, a modified edge indicator function, and a 5 35 support region for the red and blue channels are also adopted to improve the performance. With the proposed algorithm, we have achieved im- provements in the image quality especially along the edges and in the detail of the image by removing color artifacts. The superiority of the proposed algorithm is demonstrated in the experimental results. © 2004

Color interpolation algorithms in visualizing results of numerical simulations.

The paper addresses the application of graphical replenishment (GR) color interpolation algorithms for visualizing numerical simulation of physical processes in order to enhance the information density of the graphic interpretation of these processes. The GR algorithms presented here may be successfully applied to two- and three-dimensional grids, and grids of various structures.

CMOS sensor cross-talk compensation for digital cameras

This paper presents two algorithms for removing the crosstalk effect in CMOS sensor based color-imaging systems. The algorithms work on the Bayer raw data and have low computational complexity. Experimental results on Macbeth color chart and real images demonstrates that both algorithms can effectively eliminate the crosstalk effect and produce better quality images with conventional color interpolation and correction algorithms designed for CCD image sensors. Complexity of the algorithms is also analyzed.

Edge-adaptive color interpolation algorithm for progressive scan charge-coupled device image sensors

Yonsei UniversityDepartment of Electrical & ElectronicEngineering134 Shinchon, Seodaemun-KuSeoul, KoreaE-mail: mkang@yonsei.ac.krAbstract. The color interpolation scheme can play an important role inovercoming the physical limitation of CCD image sensors and in increas-ing the resolution of color signals, while most conventional approachesresult in blurred edges and false color artifacts. We propose an improvededge-adaptive color interpolation scheme for a progressive scan CCDimage sensor with an RGB color filter array. The proposed edge indicatorfunction utilizes not only the within-channel correlation, but also thecross-channel correlation, and reflects the edge characteristics of an im-age adaptively. The color components unavailable at each channel areinterpolated along the edge direction, not across the edges, so that alias-ing artifacts are suppressed. Furthermore, we eliminate false color arti-facts resulting from the color image formation model in the edge-adaptive color interpolation scheme by adopting the switching algorithmbased on the color edge detection. Simulation results of the proposedalgorithm indicate that the improved edge-adaptive color interpolationscheme produces results that are quantitatively better and visually morepleasing than those achieved by conventional approaches.