Fills a connected component with the given color

dst = cv.floodFill(src, seed, newVal)
[dst, rect, area] = cv.floodFill(src, seed, newVal)
[dst, rect, area, mask] = cv.floodFill(..., 'Mask',mask, 'MaskOnly',true)
[...] = cv.floodFill(..., 'OptionName',optionValue, ...)

Input

• src Input 1- or 3-channel, 8-bit, or floating-point image.
• seed Starting seed point [x,y].
• newVal New value of the repainted domain pixels. It should match the range and dimensions of the input image: 1-element vector (brightness) for grayscale images, and 3-element vector (color) for RGB images.

Output

• dst Destination image of the same size and the same type as src. Contains the modified input unless the MaskOnly flag is set in the second variant of the function, in which case dst is the same as the input src unmodified. See the details below.
• rect Optional output parameter set by the function to the minimum bounding rectangle of the repainted domain [x,y,w,h].
• area Optional output parameter set by the function to the number of filled pixels.
• mask Optional output containing the updated input Mask. Populated in the second variant of the function with the Mask option. On output, pixels in the mask corresponding to filled pixels in the image are set to 1 or to the value specified in MaskFillValue option as described below.

Options

• LoDiff Maximal lower brightness/color difference between the currently observed pixel and one of its neighbors belonging to the component, or a seed pixel being added to the component. default zeros
• UpDiff Maximal upper brightness/color difference between the currently observed pixel and one of its neighbors belonging to the component, or a seed pixel being added to the component. default zeros
• Connectivity Connectivity value, 4 or 8. The default value of 4 means that only the four nearest neighbor pixels (those that share an edge are considered. A connectivity value of 8 means that the eight nearest neighbor pixels (those that share a corner) will be considered. default 4
• FixedRange If set, the difference between the current pixel and seed pixel is considered. Otherwise, the difference between neighbor pixels is considered (that is, the range is floating). default false
• Mask Operation mask that should be a single-channel 8-bit image, 2 pixels wider and 2 pixels taller than image. Flood-filling cannot go across non-zero pixels in the input mask. For example, an edge detector output can be used as a mask to stop filling at edges. It is possible to use the same mask in multiple calls to the function to make sure the filled areas do not overlap. Not set by default.
• MaskOnly If set, the function does not change the image in the output (newVal is ignored), and only fills the output mask with the value specified in MaskFillValue as described. This option only make sense in function variants that have the mask parameter. default false
• MaskFillValue Value between 1 and 255 with which to fill the output Mask. This option only make sense in function variants that have the mask parameter. default 0 (which effectively flood-fills the mask by the default filling value of 1)

The function cv.floodFill fills a connected component starting from the seed point with the specified color. The connectivity is determined by the color/brightness closeness of the neighbor pixels. The pixel at (x,y) is considered to belong to the repainted domain if:

• in case of a grayscale image and floating range:

  src(x',y') - loDiff <= src(x,y) <= src(x',y') + upDiff

• in case of a grayscale image and fixed range:

  src(seedPoint.x,seedPoint.y) - loDiff <= src(x,y) <= src(seedPoint.x,seedPoint.y) + upDiff

• in case of a color image and floating range:

  src(x',y')r - loDiffr <= src(x,y)r <= src(x',y')_r + upDiffr, src(x',y')g - loDiffg <= src(x,y)g <= src(x',y')_g + upDiffg src(x',y')b - loDiffb <= src(x,y)b <= src(x',y')_b + upDiffb

• in case of a color image and fixed range:

  src(seedPoint.x,seedPoint.y)r - loDiffr <= src(x,y)r <= src(seedPoint.x,seedPoint.y)_r + upDiffr, src(seedPoint.x,seedPoint.y)g - loDiffg <= src(x,y)g <= src(seedPoint.x,seedPoint.y)_g + upDiffg src(seedPoint.x,seedPoint.y)b - loDiffb <= src(x,y)b <= src(seedPoint.x,seedPoint.y)_b + upDiffb

where src(x',y') is the value of one of pixel neighbors that is already known to belong to the component. That is, to be added to the connected component, a color/brightness of the pixel should be close enough to:

• Color/brightness of one of its neighbors that already belong to the connected component in case of a floating range.
• Color/brightness of the seed point in case of a fixed range.

Use this function to either mark a connected component with the specified color, or build a mask and then extract the contour, or copy the region to another image, and so on.

Note: Since the mask is larger than the filled image, a pixel (x,y) in image corresponds to the pixel (x+1,y+1) in the mask.