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FLOAT_TO_EXP(3)       DragonFly Library Functions Manual       FLOAT_TO_EXP(3)


NAME

       float_to_exp - Convert floating point values into "exponential" pixels.


SYNOPSIS

       #include <rle.h>

       float_to_exp( count, floats, pixels )
       int count;
       float * floats;
       rle_pixel * pixels;


DESCRIPTION

       The function float_to_exp converts count floating point numbers
       (pointed to by floats) into count+1 bytes (pointed to by pixels) using
       an "exponential" format.  This format generates count pixels as eight
       bit "mantissa" values, and another byte containing a common exponent
       for all of the data values.  This format has a wider dynamic range of
       values with little extra overhead.  The inverse mapping is
            float expnt, flt_val;
            rle_pixel exponent, val;
            expnt = ldexp( 1/256.0, (int)exponent - 127 );
            flt_val = (float)val * expnt;

       Files containing exponential data may be converted into displayable
       images using the unexp(1) command.  Unexp should be used before using
       any tools that perform arithmetic on pixel values, or displaying the
       image.  Unexp expects files containing exponential data to have an
       "exponential_data" picture comment.


SEE ALSO

       unexp(1), rle_putcom(3), librle(3), RLE(5).


AUTHOR

       John W. Peterson, based on code by Spencer Thomas.
       University of Utah

4th Berkeley Distribution      November 10, 1987               FLOAT_TO_EXP(3)

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