VipsRegion

VipsRegion — small, rectangular parts of images

Stability Level

Stable, unless otherwise indicated

Synopsis

#include <vips/vips.h>

                    VipsRegion;
                    VipsRegionClass;
VipsRegion *        vips_region_new                     (VipsImage *image);
int                 vips_region_buffer                  (VipsRegion *reg,
                                                         VipsRect *r);
int                 vips_region_image                   (VipsRegion *reg,
                                                         VipsRect *r);
int                 vips_region_region                  (VipsRegion *reg,
                                                         VipsRegion *dest,
                                                         VipsRect *r,
                                                         int x,
                                                         int y);
int                 vips_region_equalsregion            (VipsRegion *reg1,
                                                         VipsRegion *reg2);
int                 vips_region_position                (VipsRegion *reg,
                                                         int x,
                                                         int y);
void                vips_region_paint                   (VipsRegion *reg,
                                                         VipsRect *r,
                                                         int value);
void                vips_region_paint_pel               (VipsRegion *reg,
                                                         VipsRect *r,
                                                         VipsPel *ink);
void                vips_region_black                   (VipsRegion *reg);
void                vips_region_copy                    (VipsRegion *reg,
                                                         VipsRegion *dest,
                                                         VipsRect *r,
                                                         int x,
                                                         int y);
int                 vips_region_prepare                 (VipsRegion *reg,
                                                         VipsRect *r);
int                 vips_region_prepare_to              (VipsRegion *reg,
                                                         VipsRegion *dest,
                                                         VipsRect *r,
                                                         int x,
                                                         int y);
int                 vips_region_prepare_many            (VipsRegion **reg,
                                                         VipsRect *r);
#define             VIPS_REGION_LSKIP                   (R)
#define             VIPS_REGION_N_ELEMENTS              (R)
#define             VIPS_REGION_SIZEOF_LINE             (R)
#define             VIPS_REGION_ADDR                    (R,
                                                         X,
                                                         Y)
#define             VIPS_REGION_ADDR_TOPLEFT            (R)

Object Hierarchy

  GObject
   +----VipsObject
         +----VipsRegion

Description

A VipsRegion is a small part of an image and some pixels. You use regions to read pixels out of images without having to have the whole image in memory at once.

A region can be a memory buffer, part of a memory-mapped file, part of some other image, or part of some other region.

Regions must be created, used and freed all within the same thread, since they can reference private per-thread caches. VIPS sanity-checks region ownership in various places, so you are likely to see g_assert() errors if you don't follow this rule.

There is API to transfer ownership of regions between threads, but hopefully this is only needed within VIPS, so we don't expose it. Hopefully.

Details

VipsRegion

typedef struct {
	/* Users may read these two fields.
	 */
	VipsImage *im;		/* Link back to parent image */
	VipsRect valid;		/* Area of parent we can see */

	/* The rest of VipsRegion is private.
	 */
} VipsRegion;

A small part of a VipsImage. valid holds the left/top/width/height of the area of pixels that are available from the region.

See also: VIPS_REGION_ADDR(), vips_region_new(), vips_region_prepare().

VipsImage *im;

the VipsImage that this region is defined on

VipsRect valid;

the VipsRect of pixels that this region represents

VipsRegionClass

typedef struct {
	VipsObjectClass parent_class;
} VipsRegionClass;


vips_region_new ()

VipsRegion *        vips_region_new                     (VipsImage *image);

Create a region. VipsRegion s start out empty, you need to call vips_region_prepare() to fill them with pixels.

See also: vips_region_prepare().

image :

image to create this region on

vips_region_buffer ()

int                 vips_region_buffer                  (VipsRegion *reg,
                                                         VipsRect *r);

The region is transformed so that at least r pixels are available as a memory buffer.

reg :

region to operate upon

r :

VipsRect of pixels you need to be able to address

Returns :

0 on success, or -1 for error.

vips_region_image ()

int                 vips_region_image                   (VipsRegion *reg,
                                                         VipsRect *r);

The region is transformed so that at least r pixels are available directly from the image. The image needs to be a memory buffer or represent a file on disc that has been mapped or can be mapped.

reg :

region to operate upon

r :

VipsRect of pixels you need to be able to address

Returns :

0 on success, or -1 for error.

vips_region_region ()

int                 vips_region_region                  (VipsRegion *reg,
                                                         VipsRegion *dest,
                                                         VipsRect *r,
                                                         int x,
                                                         int y);

Make VIPS_REGION_ADDR() on reg go to dest instead.

r is the part of reg which you want to be able to address (this effectively becomes the valid field), (x, y) is the top LH corner of the corresponding area in dest.

Performs all clipping necessary to ensure that reg->valid is indeed valid.

If the region we attach to is modified, we can be left with dangling pointers! If the region we attach to is on another image, the two images must have the same sizeof( pel ).

reg :

region to operate upon

dest :

region to connect to

r :

VipsRect of pixels you need to be able to address

x :

postion of r in dest

y :

postion of r in dest

Returns :

0 on success, or -1 for error.

vips_region_equalsregion ()

int                 vips_region_equalsregion            (VipsRegion *reg1,
                                                         VipsRegion *reg2);

Do two regions point to the same piece of image? ie.

1
2
3
4
5
6