libvips

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().

[constructor]

vips_region_buffer ()

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

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

[method]

vips_region_image ()

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

The region is transformed so that at least r pixels are available to be read 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.

[method]

vips_region_region ()

int
vips_region_region (VipsRegion *reg,
                    VipsRegion *dest,
                    const 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 moved or destroyed, 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 ).

[method]

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

VIPS_REGION_ADDR( reg1, x, y ) == VIPS_REGION_ADDR( reg2, x, y ) &&
*VIPS_REGION_ADDR( reg1, x, y ) == 
	*VIPS_REGION_ADDR( reg2, x, y ) for all x, y, reg1, reg2.

vips_region_position ()

int
vips_region_position (VipsRegion *reg,
                      int x,
                      int y);

Set the position of a region. This only affects reg->valid, ie. the way pixels are addressed, not reg->data, the pixels which are addressed. Clip against the size of the image. Do not allow negative positions, or positions outside the image.

[method]

vips_region_paint ()

void
vips_region_paint (VipsRegion *reg,
                   const VipsRect *r,
                   int value);

Paints value into reg covering rectangle r . r is clipped against reg->valid .

For int images, value is passed to memset(), so it usually needs to be 0 or 255. For float images, value is cast to a float and copied in to each band element.

r is clipped against reg->valid .

See also: vips_region_black().

[method]

vips_region_paint_pel ()

void
vips_region_paint_pel (VipsRegion *reg,
                       const VipsRect *r,
                       const VipsPel *ink);

Paints ink into reg covering rectangle r . r is clipped against reg->valid .

ink should be a byte array of the same size as an image pixel containing the binary value to write into the pixels.

See also: vips_region_paint().

[method]

vips_region_black ()

void
vips_region_black (VipsRegion *reg);

Paints 0 into the valid part of reg .

See also: vips_region_paint().

[method]

vips_region_copy ()

void
vips_region_copy (VipsRegion *reg,
                  VipsRegion *dest,
                  const 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().

vips_region_shrink_method ()

int
vips_region_shrink_method (VipsRegion *from,
                           VipsRegion *to,
                           const VipsRect *target,
                           VipsRegionShrink method);

Write the pixels target in to from the x2 larger area in from . Non-complex uncoded images and LABQ only. Images with alpha (see vips_image_hasalpha()) shrink with pixels scaled by alpha to avoid fringing.

method selects the method used to do the 2x2 shrink.

See also: vips_region_copy().

vips_region_shrink ()

int
vips_region_shrink (VipsRegion *from,
                    VipsRegion *to,
                    const VipsRect *target);

Write the pixels target in to from the x2 larger area in from . Non-complex uncoded images and LABQ only. Images with alpha (see vips_image_hasalpha()) shrink with pixels scaled by alpha to avoid fringing.

This is a compatibility stub that just calls vips_region_shrink_method().

See also: vips_region_shrink_method().

[skip]

vips_region_prepare ()

int
vips_region_prepare (VipsRegion *reg,
                     const VipsRect *r);

vips_region_prepare() fills reg with pixels. After calling, you can address at least the area r with VIPS_REGION_ADDR() and get valid pixels.

vips_region_prepare() runs in-line, that is, computation is done by the calling thread, no new threads are involved, and computation blocks until the pixels are ready.

Use vips_sink_screen() to calculate an area of pixels in the background.

See also: vips_sink_screen(), vips_region_prepare_to().

[method]

vips_region_prepare_to ()

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

Like vips_region_prepare(): fill reg with the pixels in area r . Unlike vips_region_prepare(), rather than writing the result to reg , the pixels are written into dest at offset x , y .

Also unlike vips_region_prepare(), dest is not set up for writing for you with vips_region_buffer(). You can point dest at anything, and pixels really will be written there. This makes vips_region_prepare_to() useful for making the ends of pipelines.

See also: vips_region_prepare(), vips_sink_disc().

[method]

vips_region_invalidate ()

void
vips_region_invalidate (VipsRegion *reg);

Mark a region as containing invalid pixels. Calling this function means that the next time vips_region_prepare() is called, the region will be recalculated.

This is faster than calling vips_image_invalidate_all(), but obviously only affects a single region.

See also: vips_image_invalidate_all(), vips_region_prepare().

[method]

VIPS_COUNT_PIXELS()

#define VIPS_COUNT_PIXELS( R, N ) vips__region_count_pixels( R, N )

VIPS_REGION_LSKIP()

#define             VIPS_REGION_LSKIP( R )

VIPS_REGION_N_ELEMENTS()

#define             VIPS_REGION_N_ELEMENTS( R )

VIPS_REGION_SIZEOF_LINE()

#define             VIPS_REGION_SIZEOF_LINE( R )

VIPS_REGION_ADDR()

#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.

See also: vips_region_prepare().

VIPS_REGION_ADDR_TOPLEFT()

#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 ).

See also: vips_region_prepare().

enum VipsRegionShrink

How to calculate the output pixels when shrinking a 2x2 region.