改进的联合去马赛克与放大算法及其硬件实现
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摘要
为了从单CCD/CMOS图像探测器相机拍摄的Bayer格式图像恢复出更高分辨率全彩色图像,设计了一种改进的联合去马赛克与放大算法。首先,估计原始Bayer格式图像中丢失的绿色通道信息,根据颜色梯度的比较结果,将水平或垂直方向的绿色通道信息作为彩色图像的G分量,并根据彩色图像颜色通道之间高度相关的特性,计算颜色差R-G和B-G;然后,将去马赛克过程中的梯度方法继续用于确定丢失的绿色像素,放大绿色通道;最后,对颜色差值图像R-G和B-G进行放大,即可恢复出红色和蓝色通道信息,得到放大的全彩色图像。试验结果表明,算法恢复出的高分辨率彩色图像的峰值信噪比(PSNR)有较明显提升,且主观目视清晰、边缘锐利,特别是硬件实现方面能够做到实时处理。目前,本文算法已经在Xilinx公司的FPGA上实现,并用于工程实践。满足了项目实际需要。
In order to obtain higher resolution full color image from Bayer CFA structure image directly,this paper presents a new joint demosaicking and zooming algorithm for digital camera equipped with a single CCD/CMOS sensor.We firstly extract GHand GVcomponents of each pixel from mosaicking image through horizontal and vertical interpolations,respectively,and then we calculate and compare the horizontal chrominance gradient and the vertical one for choosing the missing G from GHand GV.By exploiting the high spectral-spatial correlations between color channels,we compute the two color difference images R-G and B-G to reduce the demosaicking and zooming errors.Next,we obtain the horizontal GzoomHand vertical GzoomVof each pixel,and also choose the missing zoomed Gzoomby calculating and comparing the chrominance gradient.Finally,the enlarged red and blue channels are obtained by adding the corresponding enlarged R-G and B-G color difference images to the enlarged green channel.Experimental results prove that the proposed algorithm outperforms some state-of-the-art demosaicking-zooming methods in both peak signal-to-noise ratio(PSNR)measure and visual quality.Furthermore,computational cost of the algorithm is low and it can be hardware processed in real time.Now,the proposed algorithm is implemented on Xilinx FPGA and used in camera system,and the perfect restoration quality and effectiveness meet the requirement of system design.
In order to obtain higher resolution full color image from Bayer CFA structure image directly,this paper presents a new joint demosaicking and zooming algorithm for digital camera equipped with a single CCD/CMOS sensor.We firstly extract GHand GVcomponents of each pixel from mosaicking image through horizontal and vertical interpolations,respectively,and then we calculate and compare the horizontal chrominance gradient and the vertical one for choosing the missing G from GHand GV.By exploiting the high spectral-spatial correlations between color channels,we compute the two color difference images R-G and B-G to reduce the demosaicking and zooming errors.Next,we obtain the horizontal GzoomHand vertical GzoomVof each pixel,and also choose the missing zoomed Gzoomby calculating and comparing the chrominance gradient.Finally,the enlarged red and blue channels are obtained by adding the corresponding enlarged R-G and B-G color difference images to the enlarged green channel.Experimental results prove that the proposed algorithm outperforms some state-of-the-art demosaicking-zooming methods in both peak signal-to-noise ratio(PSNR)measure and visual quality.Furthermore,computational cost of the algorithm is low and it can be hardware processed in real time.Now,the proposed algorithm is implemented on Xilinx FPGA and used in camera system,and the perfect restoration quality and effectiveness meet the requirement of system design.
引文
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[9]Hirakawa K,Parks T W.Adaptive homogeneity-directed demosaicing algorithm[J].IEEE Transactions on Image Processing,2005,14(3):360-369.
[10]ZHANG Lei,WU Xiao-lin.Color demosaicking via directional linear minimum mean square-error estimation[J].IEEE Transactions on Image Processing,2005,14(12):2167-2178.
[11]Daniele Menon,Stefano Andriani,Giancarlo Calvagno.Demosaicing with directional filtering and a posteriori decision[J].IEEE Transactions on Image Processing,2007,16(1):132-141.
[12]CHEN Ming,XIAO Jiang-nan,CHEN Lin,et al.The study of real-time optical OFDM transmitter based on FPGA[J].Journal of Optoelectronics·Laser,2013,24(1):63-68.陈明,肖江南,陈林,等.基于FPGA的实时光OFDM发射机的研究[J].光电子·激光,2013,24(1):63-68.
[13]Kim Gi-duck,Yoon Chang-han,Kye Sang-Bum,et al.A single FPGA-based portable ultrasound imaging system for point-of-care applications[J].IEEE Transactions on Ultrasonics,Ferroelectrics and Frequency Control,2012,59(7):1386-1394.
[14]Gonzalez C,Resano J,Plaza A,et al.FPGA implementation of abundance estimation for spectral unmixing of hyperspectral data using the image space reconstruction algorithm[J].IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing,2012,5(1):248-261.
[15]LI Hua.SDRAM based hardware design of Bayer-pattern demosaicking[J].Video Engineering,2013,37(5):49-51.李华.基于SDRAM的Bayer格式图像插值算法硬件设计[J].电视技术,2013,37(5):49-51.
[2]Lukac R,Plataniotis K N,Hatzinakos D.Color image zooming on the Bayer pattern[J].IEEE Transactions on Circuits and Systems for Video Technology,2005,15(11):1475-1492.
[3]Zhang L,Zhang D.A joint demosaicking-zooming scheme for single chip digital color cameras[J].Computer Vision and Image Understanding,2007,107(1-2):14-25.
[4]Chung K L,Chan Y H,Chen P Y,et al.New joint demosaicing and zooming algorithm for color filter array[J].IEEE Transactions on Consumer Electronics,2009,55(3):1477-1486.
[5]ZHANG Lei,LI Xin,David Zhang.Image denoising and zooming under the LMMSE framework[J].IEEE Transactions on Image Processing,2012,6(3):273-283.
[6]Chung K H,Chan Y H.A low-complexity joint color demosaicking and zooming algorithm for digital camera[J].IEEE Transactions on Image Processing,2007,16(7):1705-1715.
[7]ZHU Bo,WEN De-sheng,WANG Fei.Improved Bayer-pattern demosaicking and its hardware design[J].Journal of Optoelectronics·Laser,2012,24(6):1211-1218.朱波,汶德胜,王飞.改进的Bayer插值算法及其硬件实现[J].光电子·激光,2013,24(6):1211-1218.
[8]ZHU Bo,WEN De-sheng,WANG Fei,et al.Improvement of Bayer-pattern demosaicking with dictionary learning algorithm[J].Jounal of Electronics&Information Technology,2013,35(4):812-819.朱波,汶德胜,王飞,等.应用字典学习算法改善Bayer格式图像彩色恢复效果[J].电子与信息学报,2013,35(4):812-819.
[9]Hirakawa K,Parks T W.Adaptive homogeneity-directed demosaicing algorithm[J].IEEE Transactions on Image Processing,2005,14(3):360-369.
[10]ZHANG Lei,WU Xiao-lin.Color demosaicking via directional linear minimum mean square-error estimation[J].IEEE Transactions on Image Processing,2005,14(12):2167-2178.
[11]Daniele Menon,Stefano Andriani,Giancarlo Calvagno.Demosaicing with directional filtering and a posteriori decision[J].IEEE Transactions on Image Processing,2007,16(1):132-141.
[12]CHEN Ming,XIAO Jiang-nan,CHEN Lin,et al.The study of real-time optical OFDM transmitter based on FPGA[J].Journal of Optoelectronics·Laser,2013,24(1):63-68.陈明,肖江南,陈林,等.基于FPGA的实时光OFDM发射机的研究[J].光电子·激光,2013,24(1):63-68.
[13]Kim Gi-duck,Yoon Chang-han,Kye Sang-Bum,et al.A single FPGA-based portable ultrasound imaging system for point-of-care applications[J].IEEE Transactions on Ultrasonics,Ferroelectrics and Frequency Control,2012,59(7):1386-1394.
[14]Gonzalez C,Resano J,Plaza A,et al.FPGA implementation of abundance estimation for spectral unmixing of hyperspectral data using the image space reconstruction algorithm[J].IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing,2012,5(1):248-261.
[15]LI Hua.SDRAM based hardware design of Bayer-pattern demosaicking[J].Video Engineering,2013,37(5):49-51.李华.基于SDRAM的Bayer格式图像插值算法硬件设计[J].电视技术,2013,37(5):49-51.
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