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NAME

       IM_IMAGE_ADDR,       IM_IMAGE_SIZEOF_ELEMENT,      IM_IMAGE_SIZEOF_PEL,
       IM_IMAGE_SIZEOF_LINE, IM_IMAGE_N_ELEMENTS - macros for images

SYNOPSIS

       #include <vips/vips.h>

       int IM_IMAGE_SIZEOF_ELEMENT( im )
       IMAGE *im;

       int IM_IMAGE_SIZEOF_PEL( im )
       IMAGE *im;

       int IM_IMAGE_SIZEOF_LINE( im )
       IMAGE *im;

       int IM_IMAGE_N_ELEMENTS( im )
       IMAGE *im;

       char *IM_IMAGE_ADDR( im, x, y )
       IMAGE *im;
       int x;
       int y;

DESCRIPTION

       These macros help to simplify address arithmetic for images.

        returns sizeof( one band element ).

       IM_IMAGE_SIZEOF_PEL(3) returns sizeof( one pel ).

       IM_IMAGE_SIZEOF_LINE(3) returns sizeof( one horizontal line of pels  ).

       IM_IMAGE_N_ELEMENTS(3)  returns  the  number  of band elements across a
       horizontal line.

       IM_IMAGE_ADDR(3) returns a pointer to the pixel at  position  (x,y)  in
       the image. The point (x,y) should lie within the image.

       If  the  macro  DEBUG has been defined, then IM_IMAGE_ADDR(3) will also
       perform bounds checking. If you ask for the address of  a  pel  outside
       the  image,  then  IM_IMAGE_ADDR(3)  will print an error message of the
       form:

           IM_IMAGE_ADDR: point out of bounds, file "test.c", line 18
           (point x=50, y=0
            should have been within Rect left=0, top=0, width=50, height=50)

       and call abort(3).

       DEBUG needs to be defined *before* vips.h is  included.  Either  define
       DEBUG  with  -D  in your Makefile, or have a #define DEBUG right at the
       top of your file.

COPYRIGHT

       National Gallery, 1993

SEE ALSO

       IM_REGION_ADDR(3), im_malloc(3), im_open_local(3).

AUTHOR

       J. Cupitt - 23/7/93

                                 11 April 1990                       MACROS(3)