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 the project file as a PNG but I would like to be able to save the layered image for later editing (including any options applied to certain layers, such as text based layers).
Anyway, I have ensured that the classes that need to be written to a file are 'Serializable' but have run into a bit of a road block caused by the fact that android.graphics.Bitmap isn't serializable. The following code essentially outputs the Bitmap as a PNG into a ByteArray and should read it back in as part of 'readObject'. However, when the code runs - I can verify that the 'imageByteArrayLength' variable that is read in is the same as that which is output - but the 'Bitmap image' is always null.
Any help would be greatly appreciated. Thanks for reading.
private String title;
private int width;
private int height;
private Bitmap sourceImage;
private Canvas sourceCanvas;
private Bitmap currentImage;
private Canvas currentCanvas;
private Paint currentPaint;
private void writeObject(ObjectOutputStream out) throws IOException{
out.writeObject(title);
out.writeInt(width);
out.writeInt(height);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
currentImage.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] imageByteArray = stream.toByteArray();
int length = imageByteArray.length;
out.writeInt(length);
out.write(imageByteArray);
}
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
this.title = (String)in.readObject();
this.width = in.readInt();
this.height = in.readInt();
int imageByteArrayLength = in.readInt();
byte[] imageByteArray = new byte[imageByteArrayLength];
in.read(imageByteArray, 0, imageByteArrayLength);
BitmapFactory.Options opt = new BitmapFactory.Options();
opt.inPreferredConfig = Bitmap.Config.ARGB_8888;
Bitmap image = BitmapFactory.decodeByteArray(imageByteArray, 0, imageByteArrayLength, opt);
sourceImage = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
currentImage = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
sourceCanvas = new Canvas(sourceImage);
currentCanvas = new Canvas(currentImage);
currentPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
if ( image != null ) {
sourceCanvas.drawBitmap(image, 0, 0, currentPaint);
}
}
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);
}
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);
}
}
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);
}
}
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