Serializing and De-Serializing android.graphics.Bitmap in Java

Question

I have started work on an my first android application and have the basis of an application that handles an image with multiple layers. I am able to export a flat version of

Answer 1

Here is an example of a serializable object that can wrap bitmaps.

public class BitmapDataObject implements Serializable {

    private Bitmap currentImage;

    public BitmapDataObject(Bitmap bitmap)
    {
        currentImage = bitmap;
    }

    private void writeObject(java.io.ObjectOutputStream out) throws IOException {

        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        currentImage.compress(Bitmap.CompressFormat.PNG, 100, stream);

        byte[] byteArray = stream.toByteArray();

        out.writeInt(byteArray.length);
        out.write(byteArray);

    }

    private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {


        int bufferLength = in.readInt();

        byte[] byteArray = new byte[bufferLength];

        int pos = 0;
        do {
            int read = in.read(byteArray, pos, bufferLength - pos);

            if (read != -1) {
                pos += read;
            } else {
                break;
            }

        } while (pos < bufferLength);

        currentImage = BitmapFactory.decodeByteArray(byteArray, 0, bufferLength);

    }
}

Answer 2

It took a while, but I have found a clean solution to this problem. I produced a custom object (BitmapDataObject) that implements Serializable and has a byte[] to store the PNG data from the original Bitmap. Using this, the data is stored correctly in the ObjectOutputStream / ObjectInputStream - which effectively allows one to Serialize and Deserialize a Bitmap object by storing it as a PNG in a byte[] in a custom object. The code below resolves my query.

private String title;
private int sourceWidth, currentWidth;
private int sourceHeight, currentHeight;
private Bitmap sourceImage;
private Canvas sourceCanvas;        
private Bitmap currentImage;
private Canvas currentCanvas;   
private Paint currentPaint; 

protected class BitmapDataObject implements Serializable {
    private static final long serialVersionUID = 111696345129311948L;
    public byte[] imageByteArray;
}

/** Included for serialization - write this layer to the output stream. */
private void writeObject(ObjectOutputStream out) throws IOException{
    out.writeObject(title);
    out.writeInt(currentWidth);
    out.writeInt(currentHeight);

    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    currentImage.compress(Bitmap.CompressFormat.PNG, 100, stream);
    BitmapDataObject bitmapDataObject = new BitmapDataObject();     
    bitmapDataObject.imageByteArray = stream.toByteArray();

    out.writeObject(bitmapDataObject);
}

/** Included for serialization - read this object from the supplied input stream. */
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
    title = (String)in.readObject();
    sourceWidth = currentWidth = in.readInt();
    sourceHeight = currentHeight = in.readInt();

    BitmapDataObject bitmapDataObject = (BitmapDataObject)in.readObject();
    Bitmap image = BitmapFactory.decodeByteArray(bitmapDataObject.imageByteArray, 0, bitmapDataObject.imageByteArray.length);

    sourceImage = Bitmap.createBitmap(sourceWidth, sourceHeight, Bitmap.Config.ARGB_8888);
    currentImage = Bitmap.createBitmap(sourceWidth, sourceHeight, Bitmap.Config.ARGB_8888);

    sourceCanvas = new Canvas(sourceImage);
    currentCanvas = new Canvas(currentImage);

    currentPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    thumbnailPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    thumbnailPaint.setARGB(255, 200, 200, 200);
    thumbnailPaint.setStyle(Paint.Style.FILL);
}

Answer 3

Simply use this code for making a class BitmapDataObject. Use getters and setters to switch between Bitmap and BitmapDataObject classes.

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.Serializable;

public class BitmapDataObject implements Serializable {

    private Bitmap currentImage;

    public Bitmap getCurrentImage() {
        return currentImage;
    }

    public void setCurrentImage(Bitmap currentImage) {
        this.currentImage = currentImage;
    }

    public BitmapDataObject(Bitmap bitmap)
    {
        currentImage = bitmap;
    }

    private void writeObject(java.io.ObjectOutputStream out) throws IOException {
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        currentImage.compress(Bitmap.CompressFormat.PNG, 100, stream);
        byte[] byteArray = stream.toByteArray();
        out.writeInt(byteArray.length);
        out.write(byteArray);
    }

    private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {
        int bufferLength = in.readInt();
        byte[] byteArray = new byte[bufferLength];
        int pos = 0;
        do {
            int read = in.read(byteArray, pos, bufferLength - pos);

            if (read != -1) {
                pos += read;
            } else {
                break;
            }
        } while (pos < bufferLength);
        currentImage = BitmapFactory.decodeByteArray(byteArray, 0, bufferLength);
    }

}