1. A method for image processing, said method comprising: computing, by an image-processing device, an average bin value of a histogram for a first color channel of an image, wherein said histogram includes a plurality of bins with a determined bin size based on pixel values of a plurality of pixels in said first color channel; determining, by said image-processing device, an adaptive threshold step size for each bin of said plurality of bins in said histogram, based on a ratio of a bin value of each bin of said plurality of bins and said computed average bin value of said histogram; computing, by said image-processing device, a set of Boolean maps that correspond to a set of threshold values determined based on said determined adaptive threshold step size for each bin; generating, by said image-processing device, a saliency map of said image based on at least said computed set of Boolean maps; and adjusting, by said image-processing device, at least one auto-focus setting of an image-capturing device based on said generated saliency map of said image, said image-capturing device associated with said image-processing device.