pksieve(1)

✨ pksieve(1) ✨

okay bestie, welcome to the pksieve corner of the manual pages 💅 this is section 1, so it's a user command, and it's literally here to clean up your raster images. let's get into it 🫶

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🌸 NAME 🌸

pksieve — a program that sieve-filters raster images. yes that's the whole name. short, sweet, iconic 👑

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🎀 SYNOPSIS 🎀

pksieve -i input [-s size] -o output [options]

that's the shape of it, babe. input goes in, output comes out, and -s is optional but very much the main character when you want it 💖

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🦋 DESCRIPTION 🦋

okay so here's the vibe. pksieve filters out the little baby objects in your raster — and by "little baby" we mean maximum size defined with the option -s — and it does this by replacing them with their largest neighbor object. so the tiny speckly bits get absorbed into the big cool object next door. periodt ✨

now, what even is an "object" here? an object is pixels of the same value that are also connected. and "connected" is a choice you get to make, bestie:

• four directions — that's N-S and W-E, and you get it by setting -c 4
• eight directions — that's N-S, W-E and the diagonals NW-SE and NE-SW, and you get it by setting -c 8

pick your fighter 🌈

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💅 OPTIONS 💅

• -i filename, --input filename — the input image file. the thing you're sieving. your raw material 🍓
• -s size, --size size — raster polygons with sizes smaller than this get merged into their largest neighbour. and listen, important: no sieve is performed if size = 0. so don't be out here passing 0 and wondering why nothing happened, bestie 😭
• -o filename, --output filename — Output image file Output image file. yes it says it twice in the source and honestly? it ate. it's the output image file 💀
• -c 4|8, --connect 4|8* — the connectedness. 4 directions or 8 directions. choose wisely ✨
• -b band, --band band — the band to be used from the input file. just the one, boo 🎀
• -m filename, --mask filename — use the first band of the specified file as a validity mask. zero is invalid, non-zero is valid. so 0 = not invited to the party, anything else = you're on the list 🫶
• -ot type, --otype type — the data type for the output image. your options are literally: {Byte / Int16 / UInt16 / UInt32 / Int32 / Float32 / Float64 / CInt16 / CInt32 / CFloat32 / CFloat64}. and if you pass an empty string, it inherits the type from the input image 🦋
• -of format, --oformat format — the output image format (see also gdal_translate(1)). empty string means inherit from the input image 🌸
• -co option, --co option — creation option for the output file. multiple options can be specified, so go off, stack them, slay 💅
• -ct filename, --ct filename — a colour table in ASCII format having 5 columns: id R G B ALFA (0: transparent, 255: solid). note it's spelled ALFA in the source and we respect the source's spelling choices ✨
• -v level, --verbose level — verbose mode if > 0. so like, talk to me when you're above zero 🔥

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👑 EXAMPLE 👑

merge all patches smaller than 5 pixels into bigger classes, using 8 connectivity (horizontal, vertical and diagonal):

pksieve -i input.tif -c 8 -c 5 -o output.shp

go off, she ate, no crumbs 🌈

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sign-off time, my love 🫶 this page is from 01 January 2025, and it lives under the name pksieve(1) in the manual. now go sieve something cute 💖✨🎀