Recently, many encryption algorithms based on fractional-order chaotic system have been proposed to solve the problem of image encryption. In this paper, we propose a novel color image compression-encryption algorithm based on fractional-order hyperchaotic system and DNA coding. In the data compression stage, the data of R, G, and B channels of the color image are converted to the frequency domain by two-dimensional discrete cosine transform (DCT), and then the amount of encrypted data is reduced by the quantization process. We design a data processing algorithm to ensure that the data after DCT is compatible with DNA coding data format. In the encryption stage, the processes of DNA encoding and decoding, DNA operation, and pixel scrambling are all controlled by the corresponding chaotic sequences, which are generated by the chaotic system. The original image is used to calculate the initial state of the chaotic system, which improves the performance of the algorithm against the chosen-plaintext attack significantly. Experimental results and security analysis illustrate that the proposed algorithm has excellent compression and security performance. It can not only reconstruct the original image well under the condition of low compression ratio, but also provide high security to resist various attacks. Besides, experimental results also indicate that the algorithm proposed can be applied to the fields of color image compression, encryption, and transmission. INDEX TERMS Color image encryption, DNA encoding, fractional-order hyperchaotic system, discrete cosine transform(DCT), image compression.

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Today, the quantitative evaluation of the quality of circular or cylindrical workpieces is becoming increasingly important for the relevant industrial production sectors. Although there are already some roundness deviation evaluation algorithms available to accomplish this task, these methods are always done in a holistic way. In many industrial scenarios, however, fine evaluation of the roundness variation of local segments is often more practical than the global assessment. By performing a fine evaluation of roundness variation of local segments, crucial information that can reveal intrinsic quality characteristics of both the workpiece and the production machine can be retrieved. However, this important issue has not been well studied. To deal with this problem, a roundness deviation evaluation method based on statistical analysis of local least square circles was proposed. Experimental results illustrated that the proposed method can stably and reliably evaluate the local and global roundness deviations effectively.

Aiming at the security and efficiency of image transmission, a fast image encryption algorithm based on an improved 6-D chaotic system is proposed. Firstly, we design a hyper-chaotic system with more complex chaotic behavior, analyze the Lyapunov exponential spectrum, chaotic attractor and randomness of the system, and generate random sequences through randomness enhancement operation. Secondly, image preprocessing is used to select pixels from the original image to form a thumbnail, the size of the key space can be changed by adjusting the thumbnail. Thirdly, the hash value of the original image is used as the initial values of the hyper-chaotic system to realize the uniqueness of the key. The row encryption matrix and column encryption matrix are generated according to the maximum and minimum values of row and column pixels in the thumbnail. These two encryption matrices are composed of the full arrangement of random sequences, which refers to the random combination of random sequences in a certain order. Before the encryption, the Arnold transformation is performed on the original image and then the cipher image is obtained by row encryption and column encryption respectively. The experimental results illustrate that the proposed algorithm has excellent security performance, robustness and the speed of encryption and decryption is very fast.

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