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VIPS Reference Manual | ![]() |
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#include <vips/vips.h> #define VIPS_REGION_ADDR (R, X, Y) #define VIPS_REGION_ADDR_TOPLEFT (R) #define VIPS_REGION_LSKIP (R) #define VIPS_REGION_N_ELEMENTS (R) #define VIPS_REGION_SIZEOF_LINE (R) VipsRegion; VipsRegionClass; void vips_region_black (VipsRegion *reg
); int vips_region_buffer (VipsRegion *reg
,VipsRect *r
); void vips_region_copy (VipsRegion *reg
,VipsRegion *dest
,VipsRect *r
,int x
,int y
); int vips_region_equalsregion (VipsRegion *reg1
,VipsRegion *reg2
); int vips_region_image (VipsRegion *reg
,VipsRect *r
); VipsRegion * vips_region_new (VipsImage *image
); void vips_region_paint (VipsRegion *reg
,VipsRect *r
,int value
); void vips_region_paint_pel (VipsRegion *reg
,VipsRect *r
,VipsPel *ink
); int vips_region_position (VipsRegion *reg
,int x
,int y
); int vips_region_prepare (VipsRegion *reg
,VipsRect *r
); int vips_region_prepare_many (VipsRegion **reg
,VipsRect *r
); int vips_region_prepare_to (VipsRegion *reg
,VipsRegion *dest
,VipsRect *r
,int x
,int y
); int vips_region_region (VipsRegion *reg
,VipsRegion *dest
,VipsRect *r
,int x
,int y
);
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.
#define VIPS_REGION_ADDR( R, X, Y )
This macro returns a pointer to a pixel in a region. The (x, y) coordinates
need to be within the VipsRect (R->valid
).
If DEBUG is defined, you get a version that checks bounds for you.
|
a VipsRegion |
|
x coordinate |
|
y coordinate |
Returns : |
The address of pixel (x,y) in the region. |
#define VIPS_REGION_ADDR_TOPLEFT( R ) ((R)->data)
This macro returns a pointer to the top-left pixel in the VipsRegion, that
is, the pixel at (R->valid.left
, R->valid.top
).
|
a VipsRegion |
Returns : |
The address of the top-left pixel in the region. |
#define VIPS_REGION_LSKIP( R )
|
a VipsRegion |
Returns : |
The number of bytes to add to move down a scanline. |
#define VIPS_REGION_N_ELEMENTS( R )
|
a VipsRegion |
Returns : |
The number of band elements across a region. |
#define VIPS_REGION_SIZEOF_LINE( R )
|
a VipsRegion |
Returns : |
The number of bytes across a region. |
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()
.
void vips_region_black (VipsRegion *reg
);
Paints 0 into the valid part of reg
.
See also: vips_region_paint()
.
|
region to operate upon |
int vips_region_buffer (VipsRegion *reg
,VipsRect *r
);
The region is transformed so that at least r
pixels are available as a
memory buffer.
|
region to operate upon |
|
VipsRect of pixels you need to be able to address |
Returns : |
0 on success, or -1 for error. |
void vips_region_copy (VipsRegion *reg
,VipsRegion *dest
,VipsRect *r
,int x
,int y
);
Copy from one region to another. Copy area r
from inside reg
to dest
,
positioning the area of pixels at x
, y
. The two regions must have pixels
which are the same size.
See also: vips_region_paint()
.
|
source region |
|
destination region |
|
VipsRect of pixels you need to copy |
|
postion of r in dest
|
|
postion of r in dest
|
int vips_region_equalsregion (VipsRegion *reg1
,VipsRegion *reg2
);
Do two regions point to the same piece of image? ie.
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