Retrieves a pixel rectangle from an image with sub-pixel accuracy

dst = cv.getRectSubPix(src, patchSize, center)
dst = cv.getRectSubPix(..., 'OptionName',optionValue, ...)

Input

• src Source image, 8-bit integer or 32-bit floating-point, 1- or 3-channels.
• patchSize Size of the extracted patch [w,h].
• center Floating-point coordinates of the center of the extracted rectangle within the source image. The center [x,y] must be inside the image.

Output

• dst Extracted patch that has the size PatchSize, the same number of channels as src, and the specified type in PatchType.

Options

• PatchType Depth of the extracted pixels. By default (-1), they have the same depth as src. Supports either uint8 or single.

The function cv.getRectSubPix extracts pixels from src:

dst(x,y) = src(x + center(1) - (size(dst,2)-1)*0.5,
               y + center(2) - (size(dst,1)-1)*0.5)

where the values of the pixels at non-integer coordinates are retrieved using bilinear interpolation. Every channel of multi-channel images is processed independently. Also the image should be a single channel or three channel image. While the center of the rectangle must be inside the image, parts of the rectangle may be outside. In this case, the pixel values outside of the image are extrapolated.