IMAGE *im_open( const char *filename, const char *mode )
IMAGE *im_open_local( IMAGE *im, const char *filename, const char *mode )
int im_open_local_array( IMAGE *im,
IMAGE **out, int n, const char *filename, const char *mode )
r opens the named file for reading. If the file is not in the native VIPS format for your machine, im_open(3) automatically converts the file for you in memory. For some large files (eg. TIFF) this may not be what you want: you should call the appropriate converter yourself, and arrange for the conversion to take place on disc. See im_tiff2vips(3), im_jpeg2vips(3), im_png2vips(3), im_magick2vips(3), and im_ppm2vips(3).
im_open(3) can read files in most formats.
w opens the named file for writing. It looks at the file name suffix to determine the type to write -- for example:
im_open( "fred.tif", "w" )
will write in TIFF format.
You can pass parameters to the conversion functions encoded in the filename string. For example:
im_open( "fred.tif:deflate", "w" )
will write a deflate (ZIP) compressed TIFF file. See the man pages for im_vips2tiff(3), im_vips2jpeg(3), im_vips2png(3) and im_vips2ppm(3) for details on all of the options available.
t creates a temporary memory buffer image.
p creates a "glue" descriptor you can use to join two image processing operations together.
rw opens the named file for reading and writing. This will only work for VIPS files in a format native to your machine. It is only for paintbox-type applications.
im_open_local(3) is a convenience function which opens an image descriptor as im_open(3), but makes it local to im, that is, when im is closed, the descriptor created by im_open_local(3) will be closed too.
im_open_local(3) is handy for saving you from adding many im_close(3) calls to escape points. Example: find the total of an array of images.
#include <vips/vips.h>
int
total( IMAGE **in, int nin, IMAGE *out )
{
int i;
IMAGE *t1, *t2;
if( nin <= 0 ) {
im_errormsg( "total: nin should be > 0" );
return( -1 );
}
else if( nin == 1 )
return( im_copy( *in, out ) );
else
for( t1 = *in, i = 1; i < nin; i++ ) {
if( i + 1 == nin )
t2 = out;
else if( !(t2 = im_open_local( out, "t2", "p" )) )
return( -1 );
if( im_add( t1, in[i], t2 ) )
return( -1 );
t1 = t2;
}
return( 0 );
}
This function will create many intermediate images, but does not need to close them. Any which are created will be closed automatically when out is closed by our caller.
im_open_local(3) returns NULL on error, or if its first parameter is NULL.
im_open_local_array(3) will open an array of images, failing if any of the opens fail. It's handy if you need a number of images for intermediates. Example:
IMAGE *t[6];
if( im_open_local_array( out, t, 6, "mytemps", "p" ) )
return( -1 );
opens 6 temp images (t[0] to t[5]).