Steganography is a method of secret communication wherein the very existence of communication is hidden. During the last few decades there have been a tremendous development in digital image steganography and a large number of papers have been published by different researchers. This review paper presents a classification of the spatial domain image steganography techniques. These classifications include, (i) LSB steganography, (ii) RGB based steganography, (iii) pixel value differencing steganography, (iv) mapping based steganography, (v) palette based steganography, (vi) collage based steganography, (vii) spread spectrum steganography, and (viii) code based steganography. In image steganography the different quality measurement parameters are, (i) capacity, (ii) security, (iii) imperceptibility, (iv) temper resistance, and (v) computational complexity. Different researchers have attempted to improve the different quality measurement parameters. At the end of the paper the current promising directions of research are also pointed out.