SYNOPSIS

#include <vips/vips.h>

int im_wrapone( IMAGE *in, IMAGE *out,
    im_wrapone_fn fn, void *a, void *b )
int im_wrapmany( IMAGE **in, IMAGE *out,
    im_wrapmany_fn fn, void *a, void *b )

where

typedef void (*im_wrapone_fn)( void *in, void *out, int n,
    void *a, void *b )
typedef void (*im_wrapmany_fn)( void **in, void *out, int n,
    void *a, void *b )

DESCRIPTION

These functions provide a simple way to use the VIPS partial image IO system, provided that your image processing function involves no coordinate transformations, that is, that each output PEL depends only upon the corresponding PEL(s) in the input image(s).

You should write your operation as a buffer processing function --- for example:

    static void
    invert_buffer( unsigned char *in, unsigned char *out, 
        int width )
    {
        int x;

        for( x = 0; x < width; x++ )
            *out++ = 255 - *in++;
    }

This can now be turned into a full PIO image processing function by:

    int
    invert( IMAGE *in, IMAGE *out )
    {
        if( in->BandFmt != FMTUCHAR || 
            in->Coding != NOCODING ||
            in->Bands != 1 ) {
            im_errormsg( "invert: bad input" );
            return( -1 );
        }
        if( im_cp_desc( out, in ) )
            return( -1 );
        if( im_wrapone( in, out,
            (im_wrapone_fn) invert_buffer, NULL, NULL ) )
        return( 0 );
    }

im_wrapmany(3) works as im_wrapone(3), but allows many input images. All the inputs should be same Xsize and Ysize, but may vary in type. The array of input images should be NULL-terminated, as for im_start_many(3).

RETURN VALUE

All int-valued functions return zero on success and non-zero on error.

COPYRIGHT

National Gallery, 1995

AUTHOR

J. Cupitt - 9/2/95