Java tutorial
//package com.java2s; import android.graphics.Bitmap; import java.io.ByteArrayOutputStream; public class Main { public static byte[] bmpToByteArray(Bitmap bmp) { if (bmp == null) return null; ByteArrayOutputStream output = new ByteArrayOutputStream(); bmp.compress(Bitmap.CompressFormat.PNG, 80, output); byte[] result = output.toByteArray(); try { output.close(); } catch (Exception e) { e.printStackTrace(); } return result; } }