Wei-Jen Yang

Demosaicing of Color Filter Array Captured Images Using Gradient Edge Detection Masks and Adaptive Heterogeneity-Projection

Without demosaicing processing, this paper first proposes a new approach to extract more accurate gradient/edge information on mosaic images directly. Next, based on spectral-spatial correlation, a novel adaptive heterogeneity-projection with proper mask size for each pixel is presented. Combining the extracted gradient/edge information and the adaptive heterogeneity-projection values, a new edge-sensing demosaicing algorithm is presented. Based on 24 popular testing images, experimental results demonstrated that our proposed high-quality demosaicing algorithm has the best image quality performance when compared with several recently published algorithms.

Efficient reversible data hiding algorithm based on gradient-based edge direction prediction

Highlights? We develop a new GEDP scheme to reduce the prediction errors. ? We present an RDH algorithm based on GEDP scheme. ? We design a new systematic way to determine the appropriate thresholds. ? We propose an embedding order determination strategy to reduce distortion. ? The proposed algorithm is superior to four state-of-the-art algorithms. In this paper, we present an efficient RDH algorithm based on a new gradient-based edge direction prediction (GEDP) scheme. Since the proposed GEDP scheme can generate more accurate prediction results, the prediction errors tend to form a sharper Laplacian distribution. Therefore, the proposed algorithm can guarantee larger embedding capacity and produce better quality of marked images. The determination of appropriate thresholds is also a critical issue for a RDH algorithm, so we design a new systematic way to tackle this problem. In addition, a modified embedding order determination strategy is presented to reduce the distortion of a marked image. Based on typical test images, experimental results demonstrate the superior properties of the proposed algorithm in terms of embedding capacity and marked image quality.

Efficient reversible data hiding for color filter array images

A reversible data hiding algorithm which uses prediction errors in the color difference domain for mosaic images with the Bayer color filter array (CFA) is proposed. Furthermore, the proposed algorithm can be extended to deal with the digital time delay and integration (DTDI) mosaic images and Lukac and Plataniotis (LP) mosaic images. Experimental results on CFA, DTDI, and LP mosaic images demonstrate that the proposed algorithm can achieve high embedding capacity while maintaining good image quality.

Universal Chroma Subsampling Strategy for Compressing Mosaic Video Sequences With Arbitrary RGB Color Filter Arrays in H.264/AVC

In this paper, we propose a universal chroma subsampling strategy for compressing mosaic video sequences with arbitrary red-green-blue (RGB) color filter arrays (CFAs), which are widely used in the single sensor imaging pipeline, in H.264/AVC. We first develop a modified universal demosaicing scheme, which specifically recovers the G component in the color difference domain, to recover the missing color components in the input mosaic image frames. Then, based on the transform between the RGB and the YUV color spaces, the proposed universal subsampling strategy automatically samples, by considering the significance of the U and V components for reconstructing R and B pixels, the proper U and V chroma components according to the corresponding mosaic structure. To the best of our knowledge, this is the first universal chroma subsampling strategy designed specifically for mosaic video sequences with arbitrary RGB-CFAs. Experimental results on mosaic video sequences with seven common types of the RGB-CFAs demonstrate that the proposed universal chroma subsampling strategy is superior to the conventional strategy of H.264/AVC. Moreover, integrating the proposed universal demosaicing scheme and the chroma subsampling strategy can deliver better video sequence quality.

New joint demosaicing and zooming algorithm for color filter array

This paper presents a new joint demosaicing and zooming algorithm for digital cameras, each equipped with a single CCD/CMOS sensor and a color filter array (CFA). According to the proposed adaptive heterogeneity projection masks and Sobel- and luminance estimation-based masks, we can extract edge information of each pixel in terms of the direction of variation and the gradient from the mosaic image directly and accurately, and the extracted more accurate edge information will be utilized to assist the design of our proposed new joint demosaicing and zooming algorithm. Based on twenty-four popular testing mosaic images, our proposed new zooming algorithm has better image quality performance in terms of two objective color image quality measures, the color peak signal-to-noise ratio (CPSNR) and the S-CIELAB DeltaE* ab metric, and one subjective color image quality measure, the color artifacts, when compared with several previous zooming algorithms.

Reversible data hiding for depth maps using the depth no-synthesis-error model

When embedding hidden data in 3D images, conventional reversible data hiding methods, which are designed for 2D gray and color images, can be applied to color and depth maps. However, directly applying these methods to depth maps may cause synthesis errors and lead to visual artifacts in the rendered virtual views. Two novel reversible data hiding methods based on the depth no-synthesis-error (D-NOSE) model are proposed to embed hidden data in the depth maps of 3D images. The proposed methods can preserve the quality of the rendered virtual view and achieve substantially higher embedding capacity. Experimental results show that the proposed methods achieve better performance than the existing state-of-the-art methods in terms of both embedding capacity and the quality of the rendered virtual views.

New joint demosaicing and arbitrary-ratio resizing algorithm for color filter array based on DCT approach

This paper presents a new joint demosaicing and arbitrary-ratio resizing algorithm for mosaic images. By using the adaptive heterogeneity projection masks and Sobel- and luminance estimation-based (SL-based) masks, more accurate edge information is extracted first. Next, the fully populated green color plane is constructed by using the edge-sensing approach and color difference idea. Instead of interpolating the R and B color planes directly, the green-red color difference plane and green-blue color difference plane are therefore interpolated in order to reduce the estimation error. Next, based on the discrete cosine transform (DCT) technique, the above three constructed planes are resized to the arbitrary sized ones. Finally, the resized red and blue color planes are constructed by using the three resized planes, and then the arbitrary sized full color image is obtained. To the best of our knowledge, this is the first time that such a joint demosaicing and arbitrary-ratio resizing algorithm for mosaic images is presented. Based on twenty-four popular testing mosaic images, the proposed resizing algorithm has better image quality performance when compared with three native algorithms which are the combinations of three well-know demosaicing methods and one existing resizing method. Thus, the proposed algorithm can be used in consumer electronic products, such as digital cameras and digital camcorders, to provide the quality-efficient arbitrary-ratio resizing effect.

Efficient chroma subsampling strategy for compressing digital time delay integration mosaic video sequences in H.264/AVC

Digital time delay and integration (DTDI) mosaic video sequences captured by high-speed DTDI line-scan cameras are commonly used in industrial print inspection and high-speed capture applications. To reduce the memory requirement for saving these video sequences, it is necessary to compress them. In this paper, we present an efficient chroma subsampling strategy for compressing DTDI mosaic video sequences in H.264/AVC. Based on the color domain transform between the RGB domain and the YUV domain, a position-selection strategy is proposed to determine the two subsampling chroma components, U and V, according to the DTDI mosaic structure. The quality of reconstructed DTDI video sequences is better than those reconstructed by conventional methods. By experimenting on some popular test DTDI mosaic video sequences, the results turned out to be superior than conventional ones that adopt H.264/AVC as compression standard.

Novel quality-effective zooming algorithm for color filter array

Mosaic images are captured by a single charge-coupled device/complementary metal-oxide-semiconductor (CCD/CMOS) sensor with the Bayer color filter array. We present a new quality-effective zooming algorithm for mosaic images. First, based on adaptive heterogeneity projection masks and Sobel- and luminance-estimation-based masks, more accurate gradient information is extracted from the mosaic image directly. According to the extracted gradient information, the mosaic green ( G ) channel is first zoomed. To reduce color artifacts, instead of directly moving the original red ( R ) value to its right position and the blue ( B ) value to its lower position, the color difference interpolation is utilized to expand the G-R and G-B color difference values. Finally, the zoomed mosaic R and B channels can be constructed using the zoomed G channel and the two expanded color difference values; afterward, the zoomed mosaic image is obtained. Based on 24 popular test mosaic images, experimental results demonstrate that the proposed zooming algorithm has more than 1.79 dB quality improvement when compared with two previous zooming algorithms, one by Battiato et al. (2002) and the other by Lukac et al. (2005).

Quality-efficient syntax element-based de-interlacing method for H.264-coded video sequences with various resolutions

In this paper, we propose a novel quality-efficient de-interlacing method for H.264-coded video sequences with various resolutions. In the proposed method, using the syntax elements provided in H.264 bitstreams, four new and efficient strategies are delivered for inter-coded macroblocks to improve the quality of de-interlaced video sequences as well as alleviate the error propagation side effect. Based on the real and generated interlaced video sequences with various common resolutions, experimental results demonstrate the proposed de-interlacing method achieves better quality in terms of both objective and subjective measures when compared with the recently published method by Dong and Ngan.