ImageTools/engine/src/main/scala/com/sothr/imagetools/engine/hash/AHash.scala

package com.sothr.imagetools.engine.hash

import grizzled.slf4j.Logging

/**
  * Created by dev on 1/22/14.
  */
object AHash extends PerceptualHasher with Logging {
   def getHash(imageData: Array[Array[Int]]): Long = {
     //debug("Generating AHash")
     val width = imageData.length
     val height = imageData(0).length
     //debug(s"Image data size: ${width}x${height}")

     //calculate average pixel
     var total = 0
     for (row <- 0 until height) {
       for (col <- 0 until width) {
         total += imageData(row)(col)
       }
     }
     val mean = total / (height * width)

     //calculate ahash
     var hash = 0L
     for (row <- 0 until height by 2) {
       //process each column
       for (col <- 0 until width by 1) {
         hash <<= 1
         val pixel = imageData(row)(col)
         //If the current pixel is at or above the mean, store it as a one, else store it as a zero
         if (pixel >= mean) hash |= 1 else hash |= 0
       }

       if ((row +1) < width) {
         val nextRow = row + 1
         //process each column
         for (col <- (width - 1) to 0 by -1) {
           hash <<= 1
           val pixel = imageData(nextRow)(col)
           if (pixel >= mean) hash |= 1 else hash |= 0
         }
       }
     }
     //debug(s"Computed AHash: $hash from ${width * height} pixels")
     hash
   }
 }