如何使用Scala map reduce计算图像中的绿色像素

Question

我是 Scala 编程的新手，我正在尝试使用 Scala（尤其是绿色）计算图像中的 RGB 值。下面是仅计算绿色像素的代码。我的问题是，如何使用 Scala map reduce 算法实现相同的目标？

....
val lightGreen = new Color(0,255,0)
val darkGreen = new Color(0,100,0)

var ctrGreen = 0
var ctrTotal = 0
for (x <- 0 until w)
  for (y <- 0 until h) {
    val c = new Color(img.getRGB(x, y))
    if (isBetween(c, lightGreen,darkGreen)) {
      ctrGreen += 1
    }
    ctrTotal += 1;
  }

println("Green pixel count: " + ctrGreen)
println("Total pixel count: " + ctrTotal)

def isBetween(c: Color, c1: Color, c2: Color): Boolean = {
  c.getRed >= c1.getRed && c.getRed <= c2.getRed &&
    c.getBlue >= c1.getBlue && c.getBlue <= c2.getBlue && 
    c.getGreen <= c1.getGreen && c.getGreen >= c2.getGreen
}

如何在 Scala 中使用 map reduce 算法计算绿色像素的数量？

Answer 1

你可以改写如下：

val rangeX = (0 until w)
val rangeY = (0 until h)

val (greenPixels, allPixels) = (for ( x <- rangeX; y <- rangeY ) yield( (isGreen(x, y), 1) )).reduce( (a, b) => (a._1 + b._1, a._2 + b._2) )

或者以更实用的方式：

val (greenPixels, allPixels) = rangeX.flatMap( x => rangeY.map( y => (isGreen(x, y), 1) ) )
      .reduce( (a, b) => (a._1 + b._1, a._2 + b._2) )

格林在哪里

def isGreen(x: Int, y: Int) =
{
  val c = new Color(img.getRGB(x, y))
  val isGreenAsInt = if( isBetween(c, lightGreen,darkGreen) ) 1 else 0
  isGreenAsInt
}