Color quantization: Difference between revisions

=={{header|Kotlin}}==

{{works with|Ubuntu 16.04}}

Rather than coding this from scratch, we invoke programatically ImageMagick's 'convert' tool which has all this stuff built in.

<lang scala>// Version 1.2.41

import java.io.BufferedReader

import java.io.InputStreamReader

fun main(args: Array<String>) {

// convert 'frog' to an image which uses only 16 colors, no dithering

val pb = ProcessBuilder(

"convert",

"Quantum_frog.png",

"-dither",

"None",

"-colors",

"16",

"Quantum_frog_16.png"

)

pb.directory(null)

val proc = pb.start()

proc.waitFor()

// now show the colors used

val pb2 = ProcessBuilder(

"convert",

"Quantum_frog_16.png",

"-format",

"%c",

"-depth",

"8",

"histogram:info:-"

)

pb2.directory(null)

pb.redirectOutput(ProcessBuilder.Redirect.PIPE)

val proc2 = pb2.start()

val br = BufferedReader(InputStreamReader(proc2.inputStream))

var clrNum = 0

while (true) {

val line = br.readLine() ?: break

System.out.printf("%2d->%s\n", clrNum++, line)

}

br.close()

}</lang>

{{output}}

The resulting image is as expected and details of the 16 colors used are as follows:

<pre>

0-> 37572: ( 9, 53, 0) #093500 srgb(9,53,0)

1-> 7068: ( 13, 26, 0) #0D1A00 srgb(13,26,0)

2-> 31: ( 15,165, 21) #0FA515 srgb(15,165,21)

3-> 19609: ( 42, 96, 1) #2A6001 srgb(42,96,1)

4-> 21753: ( 57,136, 4) #398804 srgb(57,136,4)

5-> 66865: ( 77,147, 10) #4D930A srgb(77,147,10)

6-> 12275: ( 79,111, 9) #4F6F09 srgb(79,111,9)

7-> 836: ( 94,111, 74) #5E6F4A srgb(94,111,74)

8-> 25689: (105,158, 28) #699E1C srgb(105,158,28)

9-> 5095: (113,163, 85) #71A355 srgb(113,163,85)

10-> 1788: (125,129,151) #7D8197 srgb(125,129,151)

11-> 12929: (145,172, 31) #91AC1F srgb(145,172,31)

12-> 13245: (158,200, 51) #9EC833 srgb(158,200,51)

13-> 17024: (175,210, 86) #AFD256 srgb(175,210,86)

14-> 7913: (177,192, 99) #B1C063 srgb(177,192,99)

15-> 12452: (202,217,188) #CAD9BC srgb(202,217,188)

</pre>