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feat(compress): SVD approximation of image

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This commit is contained in:
Mahdi Dibaiee 2016-10-08 18:14:47 +03:30
parent 547a44eacb
commit 283ff57955
3 changed files with 31 additions and 10 deletions
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3
README.md
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@ -16,6 +16,9 @@ Options:
--rotate <n> - rotate image by n degrees
--grayscale - turn the image grayscale
--invert - invert (negative) the image
--compress <n> - approximate the (width - n)-th rank of image using SVD
a number between 0 (no compression) and image width (full compression)
note: this is not size compression
--output <filename> - output name, defaults to 'output.png'
```

9
app/Main.hs
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@ -11,6 +11,7 @@ module Main where
, argContrast :: Double
, argGamma :: Int
, argBrightness :: Double
, argCompress :: Int
}
opts = Options { file = ""
@ -22,6 +23,7 @@ module Main where
, argContrast = 0
, argGamma = 1
, argBrightness = 0
, argCompress = 0
}
main :: IO ()
@ -39,6 +41,7 @@ module Main where
putStrLn " --rotate <n> - rotate image by n degrees"
putStrLn " --grayscale - turn the image grayscale"
putStrLn " --invert - invert (negative) the image"
putStrLn " --compress <n> - approximate the (width - n)-th rank of image using SVD, note: this is not size compression, a number between 0 (no compression) and image width (full compression)"
putStrLn " --output <filename> - output name, defaults to output.png"
else do
let options = parseArgs args opts
@ -54,8 +57,9 @@ module Main where
. gamma (argGamma options)
. brightness (argBrightness options)
. conditionalFn grayscale (argGrayscale options)
. conditionalFn invert (argInvert options) $ p
writePicturePng "output.png" edited
. conditionalFn invert (argInvert options)
. compress (argCompress options) $ p
writePicturePng (output options) edited
return ()
@ -72,6 +76,7 @@ module Main where
parseArgs ("--contrast":n:rest) opts = parseArgs rest (opts { argContrast = read n })
parseArgs ("--brightness":n:rest) opts = parseArgs rest (opts { argBrightness = read n })
parseArgs ("--gamma":n:rest) opts = parseArgs rest (opts { argGamma = read n })
parseArgs ("--compress":n:rest) opts = parseArgs rest (opts { argCompress = read n })
parseArgs ("--output":n:rest) opts = parseArgs rest (opts { output = n })
parseArgs (name:rest) opts = parseArgs rest (opts { file = name })

19
src/Data/Picture.hs
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@ -20,6 +20,7 @@ module Data.Picture ( Picture
, brightness
, gamma
, invert
, compress
-- * Converting between Image and Picture
, fromImage
, toImage
@ -34,6 +35,7 @@ module Data.Picture ( Picture
import qualified Data.Vector.Storable as V
import System.IO
import Data.Maybe
import Debug.Trace
-- | (R, G, B) color channels
type Picture = (Matrix Double, Matrix Double, Matrix Double)
@ -108,9 +110,8 @@ module Data.Picture ( Picture
where
f = cmap (`subtract` 255)
{- | Rotate 'Picture' for the specified degrees, around the specified origin.
- If the origin is `Nothing`, rotates around the center
-}
-- | Rotate 'Picture' for the specified degrees, around the specified origin.
-- If the origin is `Nothing`, rotates around the center
rotate :: Double -> Maybe (Int, Int) -> Picture -> Picture
rotate deg orig (r, g, b) = (f r, f g, f b)
where
@ -135,5 +136,17 @@ module Data.Picture ( Picture
f m = reshape (cols m) $ fromList $ map (\[x, y] -> if y < 0 || y >= rows r || x < 0 || x >= cols r then 255 else m `atIndex` (y, x)) movedIndices
-- | Compress the image using SVD
-- note: this is not size compression, it's just a k-rank approximation of the image
compress :: Int -> Picture -> Picture
compress rate (r, g, b) = (f r, f g, f b)
where
k = cols r - rate
f m =
let (u, s, v) = svd m
si = diagRect 0 s (rows m) (cols m)
(mu, ms, mv) = (u ?? (All, Take k), si ?? (Take k, Take k), (tr v) ?? (Take k, All))
in mu <> ms <> mv
bound (l, u) x = max l $ min u x
pixelBound = bound (0, 255)