Abstract: In this paper , the effects of colors in different gray scales on mortar appearance were studied by the image processing techniques , and the characterization methods of the efflorescence degree of decorative mortar were studied on this basis .The results show that the gray scales of colors in efflorescence region would affect mortar appearance when they were 15 higher than that of matrix color . The percentage of the pixel in different gray values in the mortar sample image ( pi ) was extracted, and then a formula f =Σj=255i=bi+16 ri ×pi was proposed to evaluate the extent of efflorescence , ri represent influence modulus of colors in different gray values .P20,70 ×R70,1 =F20,1 were set up by combining with numerical evaluations of the mortar efflorescence degree by volunteers , and solution of the matrix equation represents ri,respectively,then ri and gi linear fit and get fit function:ri = gi -bi100 ×(240-bi) ×(255-bi), (gi>bi).Experimental results prove that the calculated value of the formula can not only feature the efflorescence extent well but has a good conformance with the evaluation value .

Key words: decorative mortar;image gray scale;efflorescence;characterization method