java - How can I make this ImageBrightener method function properly? -

this imagebrightener method supposed brighten image increasing color values. each value should increase half distance between , 255. thus, 155 go 205 while 205 go 230 , on. can figure out issue imagebrightener! thanks

import squint.simage; public class imagebrightener implements imagetransformer {      @override     public simage transform(simage picture) {         return brightenimage(picture);     }      private static simage brightenimage(simage si) {         int[][] newreds = brightenimagesinglechannel(si.getredpixelarray());         int[][] newgreens = brightenimagesinglechannel(si.getgreenpixelarray());         int[][] newblues = brightenimagesinglechannel(si.getbluepixelarray());          return new simage(newreds, newgreens, newblues);     }      // here code brighten image , not functioning     private static int[][] brightenimagesinglechannel(int[][] pixelarray) {         private static int[][] brightenimagesinglechannel(int[][] pixelarray) {             int columns = pixelarray.length;             int rows = pixelarray[0].length;             int[][] answer = new int[columns][rows];             (int x = 0; x < columns; x++) {                 (int y = 0; y < rows; y++) {                     answer[x][y] = 255 - pixelarray[x][y] ;                     answer[x][y] = answer[x][y] + pixelarray[x][y] ;                 }             }             return answer;         }     }      // here functioning code darkening image.     private static int[][] darkenimagesinglechannel(int[][] pixelarray) {         int columns = pixelarray.length;         int rows = pixelarray[0].length;         int[][] answer = new int[columns][rows];         (int x = 0; x < columns; x++) {             (int y = 0; y < rows; y++) {                 answer[x][y] = (255 * 2) / 3 - pixelarray[x][y];             }         }         return answer;     } } 

the problem here

answer[x][y] = 255 - pixelarray[x][y] ; answer[x][y] = answer[x][y] + pixelarray[x][y] ; 

answer[x][y] 255.

try this

answer[x][y] = (pixelarray[x][y] + 255) / 2;