感觉很有用...保存......

 

第一个是使用了乘法的版本

u32 approx_distance( s32 dx, s32 dy )

{

 u32 min, max, approx; if ( dx < 0 ) dx = -dx;

 if ( dy < 0 ) dy = -dy; if ( dx < dy )

 {

 min = dx;

 max = dy;

 } else {

 min = dy;

 max = dx;

 } approx = ( max * 1007 ) + ( min * 441 );

 if ( max < ( min << 4 ))

 approx -= ( max * 40 ); // add 512 for proper rounding

 return (( approx + 512 ) >> 10 );

}

 

 

 

 

 

int approx_distance2D( int dx, int dy )

{

int min, max;

if ( dx < 0 ) dx = -dx;

if ( dy < 0 ) dy = -dy;

if ( dx < dy )

{

min = dx;

max = dy;

} else {

min = dy;

max = dx;

}

// coefficients equivalent to ( 123/128 * max ) and ( 51/128 * min )

return ((( max << 8 ) + ( max << 3 ) - ( max << 4 ) - ( max << 1 ) +

( min << 7 ) - ( min << 5 ) + ( min << 3 ) - ( min << 1 )) >> 8 );

}