Floyd-Steinberg Algorithm

Center for Biometrics and Security Research

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The following code snippet (in floyd.m) does the dithering and displays the result in a window. You can make it happen by typing floyd(am);

function b=floyd(a)
width=size(a,2);
height=size(a,1);
err=zeros(size(a));
for x=1:width,
        for y=1:height,
                if (a(y,x)+err(y,x))<128, b(y,x)=0;
                else b(y,x)=255; 
                end;
                diff=(a(y,x)+err(y,x))-b(y,x);
                if x<width, err(y,x+1)=err(y,x+1)+diff*7/16; end;
                if y<height, 
                        err(y+1,x)=err(y+1,x)+diff*5/16;
                        if x>1, err(y+1,x-1)=err(y+1,x-1)+diff*3/16; end;
                        if x<width err(y+1,x+1)=err(y+1,x+1)+diff*1/16; end;
                end;
        end;
end;
f=figure('Position',[512,512,width,height]);
colormap(gray(256));
g=axes('Position',[0,0,1,1]); 
image(b);