blockhash 
This is a perceptual image hash calculation tool based on algorithm described in Block Mean Value Based Image Perceptual Hashing by Bian Yang, Fan Gu and Xiamu Niu. Visit the website for further information.
Program
Usage: blockhash [-q|--quick] [-b|--bits ARG] filenames
blockhash
Available options:
-h,--help Show this help text
-q,--quick Use quick hashing method
-b,--bits ARG Create hash of size N^2 bits.
Library
The example code below uses JuicyPixels to load images and prints the hash to stdout.
import qualified Codec.Picture as P
import Data.Blockhash
import qualified Data.Vector.Generic as VG
import qualified Data.Vector.Unboxed as V
printHash :: FilePath -> IO ()
printHash filename = do
res <- P.readImage filename
case res of
Left err -> putStrLn ("Fail to read: " ++ filename)
Right dynamicImage -> do
let rgbaImage = P.convertRGBA8 dynamicImage
pixels = VG.convert (P.imageData rgbaImage)
image = Image { imagePixels = pixels
, imageWidth = P.imageWidth rgbaImage
, imageHeight = P.imageHeight rgbaImage }
hash = blockhash image 16 Precise
putStrLn (show hash)