PImage to byte array for use with Android's BitmapFactory

Android Processing

Xian

PImage to byte array for use with Android's BitmapFactory

in Android Processing • 1 month ago

Hi everyone,

I'm trying to use this code from Daniel Shiffman, translating the necessary parts to Android's graphics library (since Android doesn't include awt libraries). http://shiffman.net/2010/11/13/streaming-video-with-udp-in-processing/ I'm basically trying to stream video from an Android tablet to a Processing sketch running on a PC, both connected to the same WiFi network. Like using the tablet as a wireless webcam. NOTE: I'm using a still to test this out but I'll use the tablet's camera, that's why I can't use "file to byte array" methods.

I have to convert a PImage to a byte array that is usable with Android's BitmapFactory.decodeByteArray() . How do I do that?

I tried looping through the pixels[] and passing it to an int array but, when I translate this to bytes, the BitmapFactory can't use it.

BitmapFactory docs: http://developer.android.com/reference/android/graphics/BitmapFactory.html

Here is the image I'm using: http://3.bp.blogspot.com/-GMpXUe3kKkU/Tgn5CInbVxI/AAAAAAAAIpQ/cs0AICtd9Ao/s320/picasso_woman_b.jpg

Thanks in advance for all the help you can give me!!

Here is the code so far (Line 61 is how I know my byte array is not working, it returns null):

import java.net.*;
import java.io.*;
import java.nio.*;
import ketai.net.*;
import android.graphics.*;
PImage myimg;
int[] myPixels;
int clientPort = 9100;
DatagramSocket ds;
String myIPAddress;
String remoteAddress = "192.168.0.104";//PC Local IP address. REPLACE WITH YOUR IP ADDRESS
void setup()
{
size(192,262);
orientation(PORTRAIT);
imageMode(CENTER);
myIPAddress = KetaiNet.getIP();
myimg = loadImage("picasso_woman_b.jpg");
try
{
ds = new DatagramSocket();
}
catch (SocketException e)
{
e.printStackTrace();
}
broadcast(myimg);
}
void draw()
{
image(myimg,width/2 , height/2);
}
void broadcast(PImage img)
{
//Convertir pixels[] en int[]
myPixels = new int[img.width*img.height];
img.loadPixels();
for(int i = 0; i<img.width*img.height; i++)
{
myPixels[i]= img.pixels[i];
}
//Convert int[] to byte[]
ByteBuffer byteBuffer = ByteBuffer.allocate(img.width*img.height * 4);
IntBuffer intBuffer = byteBuffer.asIntBuffer();
intBuffer.put(myPixels);
byte[] imgByteArray = byteBuffer.array();
//Use byte[] with BitmapFactory
Bitmap bitmap = BitmapFactory.decodeByteArray(imgByteArray, 0, imgByteArray.length);
println(bitmap);//HERE IS WHERE I FOUND MY BYTE ARRAY IS NOT VALID, SINCE IT RETUNRS NULL
// Need these output streams to get image as bytes for UDP communication
ByteArrayOutputStream baStream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 50, baStream);//Compress bitmap to be able to stream it
BufferedOutputStream bos = new BufferedOutputStream(baStream);
// Get the byte array, which we will send out via UDP!
byte[] packet = baStream.toByteArray();
// Send JPEG data as a datagram
println("Sending datagram with " + packet.length + " bytes");
try
{
ds.send(new DatagramPacket(packet,packet.length, InetAddress.getByName(remoteAddress),clientPort));
}
catch (Exception e)
{
e.printStackTrace();
}
}

Replies(3)

dimkir

Re: PImage to byte array for use with Android's BitmapFactory

1 month ago

You won't be able to do this directly. The arguments of BitmapFactory.decodeByteArray() take bytes of compressed image-file (ie JPG, PNG)

Whereas PImage is at best just a "raw-pixel-data". You need to "compress" it first, before feeding to decodeByteArray(). So this is not the method you need. (As it doesn't make sense compressing it to decompress and compress it again for sending).

I found the link below, which shows how to convert pixels[] array into android bitmap. Hopefully it works for you:

http://stackoverflow.com/questions/7850185/converting-array-of-int-to-bitmap-on-android

Xian

Re: PImage to byte array for use with Android's BitmapFactory

1 month ago

Thank you so much dimkir for pointing me in the right direction. I didn't actually use the most voted answer but another one from the same post. Basically this:

Bitmap bmp = Bitmap.createBitmap(img.width, img.height, Bitmap.Config.ARGB_8888);
bmp.setPixels(myPixels, 0, img.width, 0, 0, img.width, img.height);\

Being img an instance of PImage and myPixels an int[] copy of the pixels[].

Already tested and working for video streaming using the Ketai library :)

dimkir

Re: PImage to byte array for use with Android's BitmapFactory

1 month ago

Great to know you found the answer!

Would be nice to see the end result of your sketch when it's ready. Be sure to share it on github! ;)

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