Image gradient, as a preprocessing step is an essential tool in image processing in many research areas such as edge detection, segmentation, smoothing, inpainting, etc. In the present paper, we develop a new gradient by integrated the quaternion framework with LPA-ICI (local polynomial approximation – the intersection of confidence intervals) based on anisotropic gradient concepts for the color image processing applications. Computer simulations on the Berkeley Segmentation Dataset show that the new quaternion anisotropic gradient exhibits fewer color artifacts compared to state-of-the-art techniques including well-knowledge gradient operators.
The research problem is to find an effective enhancement method for enhancing raw underwater color images. In underwater, as depth increases the high wavelength regions of the light spectrum are absorbed by the water and the light spectrum consists only of low wavelength regions such as green and blue and therefore, the image captured underwater looks green or greenish blue. This paper proposes an enhancement algorithm for improving the quality of raw underwater images by the method of alpha-rooting by two-side 2-D quaternion discrete Fourier transform (QDFT) with color correction done by multiscale retinex (MSR). The results of proposed enhancement are compared with the alpha-rooting method, by transforming color images to 2-D grayscale images. The enhancement are measured with reference to the metric color enhancement measure estimation.