Bresenham画直线,任意斜率

  function DrawLineBresenham(x1,y1,x2,y2)

%sort by x,sure x1<x2.

if x1>x2

    tmp=x1;

    x1=x2;

    x2=tmp;

    tmp=y1;

    y1=y2;

    y2=tmp;

end

dx=x2-x1;

dy=y2-y1;

twoDy=2*dy;

twoDy_Dx=2*(dy-dx);

twoDx=2*dx;

twoDx_Dy=2*(dx-dy);

twoDxPlusDy=2*(dx+dy);

%branch 1: k>0 ?

%k>0 <=> dy>0

if dy>0  %k>0

    if dx==0   %if k==INF

        for i=y1:y2

            plot(x1,i,'*');

            hold('on');

        end

        return ;

    end

    %branch 2:k=INF

    %branch 3: k<1 <=> dy<dx

    if dy<dx   %k<1

          p=  twoDy-dx;

          plot(x1,y1,'*');

          hold('on');

          while x1<x2

               x1=x1+1;

               if(p<0)

                   p=p+twoDy;

               else

                   y1=y1+1;

                   p=p+twoDy_Dx;

               end

               plot(x1,y1,'*');

               hold('on');

          end

    elseif dy>dx  %k>1

          p =dy;

          plot(x1,y1,'*');

          hold('on');

          while y1<y2

              y1=y1+1;

              if p<0

                  p=p+twoDx;

              else

                  x1=x1+1;

                  p=p+twoDx_Dy;

              end

              plot(x1,y1,'*');

              hold('on');

          end

    else          %k==1

        for i=x1:x2

            plot(i,y1-x1+i,'*');

             hold('on');

        end

    end

elseif dy<0  %k<0

    if dx==0   %if k==INF

        for i=y2:y1

            plot(x1,i,'*');

            hold('on');

        end

        return ;

    end

    if dx+dy>0 %-1<k<0

      p=twoDy+dx;

      plot(x1,y1,'*');

      hold('on');

      while x1<x2

         x1=x1+1;

         if p<0

             y1=y1-1;

             p=p+twoDxPlusDy;

         else

             p=p+twoDy;

         end

         plot(x1,y1,'*');

         hold('on');

      end

    elseif dx+dy<0 %k>-1

        p=twoDx-dy;

        plot(x1,y1,'*');

        hold('on');

        while y1>y2

              y1=y1-1;

              if p<0

                  x=x+1;

                  p=p-twoDxPlusDy;

              else

                  p=p-twoDx;

              end

              plot(x1,y1,'*');

              hold('on');

        end

    else %k==-1

        for i=x1:x2

            plot(i,y1+x1-i,'*');

             hold('on');

        end

    end

else     %k==0

       for i=x1:x2

            plot(i,y1,'*');

            hold('on');

        end

end

% y2=flag*y2;

% y1=flag*y1;

% dx=(x2-x1);

% dy=(y2-y1);

% d=[];

% d(1)=2*dy-dx;

% DoubleDy=2*dy;

% DoubleDy_x=2*(dy-dx);

% x=[];

% y=[];

% x(1)=x1;

% y(1)=y1;

% for i=2:10

%     x(i)=x(i-1)+1;

%     if d(i-1)<0

%         d(i)=d(i-1)+DoubleDy;

%         y(i)=y(i-1);

%     else

%         d(i)=d(i-1)+DoubleDy_x;

%         y(i)=y(i-1)+1;

%     end

% end

% grid on

% plot(x,y,'*');

% grid on

% hold on

% k1=(y2-y1)/(x2-x1);

% b=y2-k1*x2;

% x_a=x1:0.1:x2;

% y_a=k1*x_a+b;

% plot(x_a,y_a);

% title('Bresenham画直线算法');

end