:param p:0-based coordinate of the extrapolated pixel along one of the axes,
likely <0 or >= ``len`` .
:param len:Length of the array along the corresponding axis.
:param borderType:Border type, one of the ``BORDER_*`` , except for ``BORDER_TRANSPARENT``
and ``BORDER_ISOLATED`` . When ``borderType==BORDER_CONSTANT`` , the
function always returns -1, regardless of ``p`` and ``len`` .
The function computes and returns the coordinate of a donor pixel corresponding to the specified
extrapolated pixel when using the specified extrapolation border mode. For example, if you use
``BORDER_WRAP`` mode in the horizontal direction, ``BORDER_REFLECT_101`` in the vertical direction
and want to compute value of the "virtual" pixel ``Point(-5, 100)`` in a floating-point image
``img`` , it looks like: ::
float val = img.at<float>(borderInterpolate(100, img.rows, BORDER_REFLECT_101),
borderInterpolate(-5, img.cols, BORDER_WRAP));
Normally, the function is not called directly. It is used inside :ocv:class:`FilterEngine`
and :ocv:func:`copyMakeBorder` to compute tables for quick extrapolation.
..seealso::
:ocv:class:`FilterEngine`,
:ocv:func:`copyMakeBorder`
copyMakeBorder
--------------
Forms a border around an image.
..ocv:function:: void copyMakeBorder( InputArray src, OutputArray dst, int top, int bottom, int left, int right, int borderType, const Scalar& value=Scalar() )
:param p:0-based coordinate of the extrapolated pixel along one of the axes, likely <0 or >= ``len`` .
:param len:Length of the array along the corresponding axis.
:param borderType:Border type, one of the ``BORDER_*`` , except for ``BORDER_TRANSPARENT`` and ``BORDER_ISOLATED`` . When ``borderType==BORDER_CONSTANT`` , the function always returns -1, regardless of ``p`` and ``len`` .
The function computes and returns the coordinate of a donor pixel corresponding to the specified extrapolated pixel when using the specified extrapolation border mode. For example, if you use ``BORDER_WRAP`` mode in the horizontal direction, ``BORDER_REFLECT_101`` in the vertical direction and want to compute value of the "virtual" pixel ``Point(-5, 100)`` in a floating-point image ``img`` , it looks like: ::
float val = img.at<float>(borderInterpolate(100, img.rows, BORDER_REFLECT_101),
borderInterpolate(-5, img.cols, BORDER_WRAP));
Normally, the function is not called directly. It is used inside
:ocv:class:`FilterEngine` and
:ocv:func:`copyMakeBorder` to compute tables for quick extrapolation.
..seealso::
:ocv:class:`FilterEngine`,
:ocv:func:`copyMakeBorder`
boxFilter
---------
Blurs an image using the box filter.
@ -537,63 +506,6 @@ The function constructs a vector of images and builds the Gaussian pyramid by re
:ocv:func:`pyrDown` to the previously built pyramid layers, starting from ``dst[0]==src`` .
copyMakeBorder
--------------
Forms a border around an image.
..ocv:function:: void copyMakeBorder( InputArray src, OutputArray dst, int top, int bottom, int left, int right, int borderType, const Scalar& value=Scalar() )
:param dst:Destination image of the same type as ``src`` and the size ``Size(src.cols+left+right, src.rows+top+bottom)`` .
:param top:
:param bottom:
:param left:
:param right:Parameter specifying how many pixels in each direction from the source image rectangle to extrapolate. For example, ``top=1, bottom=1, left=1, right=1`` mean that 1 pixel-wide border needs to be built.
:param borderType:Border type. See :ocv:func:`borderInterpolate` for details.
:param value:Border value if ``borderType==BORDER_CONSTANT`` .
The function copies the source image into the middle of the destination image. The areas to the left, to the right, above and below the copied source image will be filled with extrapolated pixels. This is not what
:ocv:class:`FilterEngine` or filtering functions based on it do (they extrapolate pixels on-fly), but what other more complex functions, including your own, may do to simplify image boundary handling.
The function supports the mode when ``src`` is already in the middle of ``dst`` . In this case, the function does not copy ``src`` itself but simply constructs the border, for example: ::
// let border be the same in all directions
int border=2;
// constructs a larger image to fit both the image and the border
Mat gray_buf(rgb.rows + border*2, rgb.cols + border*2, rgb.depth());
// select the middle part of it w/o copying data
Mat gray(gray_canvas, Rect(border, border, rgb.cols, rgb.rows));
// convert image from RGB to grayscale
cvtColor(rgb, gray, CV_RGB2GRAY);
// form a border in-place
copyMakeBorder(gray, gray_buf, border, border,
border, border, BORDER_REPLICATE);
// now do some custom filtering ...
...
..note::
When the source image is a part (ROI) of a bigger image, the function will try to use the pixels outside of the ROI to form a border. To disable this feature and always do extrapolation, as if ``src`` was not a ROI, use ``borderType | BORDER_ISOLATED``.
Andrey Kamaev
12 years ago