Bitmap/Histogram: Difference between revisions
Added Kotlin
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The [https://raw.githubusercontent.com/MichaeLeroy/rosetta-code/master/julia/completed/bitmap_histogram_in.jpg input] and [https://raw.githubusercontent.com/MichaeLeroy/rosetta-code/master/julia/completed/bitmap_histogram_out.png output] files.
=={{header|Kotlin}}==
Uses the image from the [[Percentage difference between images]] task as an example.
<lang scala>// version 1.2.10
import java.io.File
import java.awt.image.BufferedImage
import javax.imageio.ImageIO
const val BLACK = 0xff000000.toInt()
const val WHITE = 0xffffffff.toInt()
fun luminance(argb: Int): Int {
val red = (argb shr 16) and 0xFF
val green = (argb shr 8) and 0xFF
val blue = argb and 0xFF
return (0.2126 * red + 0.7152 * green + 0.0722 * blue).toInt()
}
val BufferedImage.histogram: IntArray
get() {
val lumCount = IntArray(256)
for (x in 0 until width) {
for (y in 0 until height) {
var argb = getRGB(x, y)
lumCount[luminance(argb)]++
}
}
return lumCount
}
fun findMedian(histogram: IntArray): Int {
var lSum = 0
var rSum = 0
var left = 0
var right = 255
do {
if (lSum < rSum) lSum += histogram[left++]
else rSum += histogram[right--]
}
while (left != right)
return left
}
fun BufferedImage.toBlackAndWhite(median: Int) {
for (x in 0 until width) {
for (y in 0 until height) {
val argb = getRGB(x, y)
val lum = luminance(argb)
if (lum < median)
setRGB(x, y, BLACK)
else
setRGB(x, y, WHITE)
}
}
}
fun main(args: Array<String>) {
val image = ImageIO.read(File("Lenna100.jpg"))
val median = findMedian(image.histogram)
image.toBlackAndWhite(median)
val bwFile = File("Lenna_bw.jpg")
ImageIO.write(image, "jpg", bwFile)
}</lang>
=={{header|Lua}}==
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