| .TH MACROS 3 "11 April 1990" |
| .SH NAME |
| IM_REGION_ADDR, |
| IM_REGION_LSKIP, |
| IM_REGION_N_ELEMENTS, IM_REGION_SIZEOF_LINE \- |
| macros for regions |
| .SH SYNOPSIS |
| .B #include <vips/vips.h> |
| |
| int IM_REGION_LSKIP( reg ) |
| .br |
| REGION *reg; |
| |
| int IM_REGION_N_ELEMENTS( reg ) |
| .br |
| REGION *reg; |
| |
| int IM_REGION_SIZEOF_LINE( reg ) |
| .br |
| REGION *reg; |
| |
| char *IM_REGION_ADDR( reg, x, y ) |
| .br |
| REGION *reg; |
| .br |
| int x, y; |
| |
| .SH DESCRIPTION |
| These macros help to simplify address arithmetic for regions. |
| |
| IM_REGION_LSKIP(3) returns the number of *bytes* you should add to move |
| down a scan line. Remember that if your pointer has been cast to the type |
| of the image pels, this will not be the correct amount to add! The value |
| lskip returns can be changed by a call to im_prepare(3). |
| |
| IM_REGION_N_ELEMENTS(3) returns the number of band elements across the region. |
| |
| IM_REGION_SIZEOF_LINE(3) returns sizeof( horizontal line across region ). |
| |
| IM_REGION_ADDR(3) returns a pointer to the pixel at position (x,y) in the |
| image on which reg has been defined. The point (x,y) should lie within the |
| valid area for this region. |
| |
| If the macro DEBUG has been defined, then IM_REGION_ADDR(3) will also |
| perform bounds checking. If you ask for the address of a pel outside the rect |
| reg->valid, then IM_REGION_ADDR(3) will print an error message of the form: |
| |
| IM_REGION_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* region.h is included. Either define DEBUG |
| with -D in your Makefile, or have a #define DEBUG right at the top of your |
| file. |
| |
| .SH COPYRIGHT |
| National Gallery, 1993 |
| .SH SEE ALSO |
| IM_IMAGE_ADDR(3), im_malloc(3), im_open_local(3). |
| .SH AUTHOR |
| J. Cupitt \- 23/7/93 |
