rank_n — Return gray values with given rank from multiple channels.
The operator rank_n returns pixel-by-pixel the result of the rank-function over all channels.
For every pixel in the input image the following is being done: The gray values of all channels at this position are sorted in ascending order. Then the pixel with index RankIndex is selected and placed in the output image at the same position. The output image has one channel.
In the special cases RankIndex = 1 and RankIndex = '(Number of channels)' the minimum and maximum are returned. RankIndex = '(Number of channels + 1) / 2' returns the median (here, / denotes integer division). Hence, for a five-channel image, 3 returns the median.
The operator rank_n should not be confused with the operator rank_image which computes the rank within a certain mask.
Multichannel gray image.
Result of the rank function.
Rank of the gray value images to return.
Default value: 2
Suggested values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20
compose5 (Image1, Image2, Image3, Image4, Image5, MultiChannelImage) rank_n (MultiChannelImage, ImageMin, 1) rank_n (MultiChannelImage, ImageMax, 5) rank_n (MultiChannelImage, ImageMedian, 3)
compose2, compose3, compose4, compose5, add_channels