MACROS(3)

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. IM_IMAGE_SIZEOF_ELEMENT(3) 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_malloc(3), im_open_local(3), `VIPS Library Programmers' Guide' in accompanying documentation.

AUTHOR
J. Cupitt - 23/7/93