decodeByteArray和copyPixelsToBuffer无法正常工作.SkImageDecoder :: Factory返回null

Question

我有一个类TouchPoint,它实现了Serializable,因为它包含Bitmap,我为该类编写了writeObject和readObject:

private void writeObject(ObjectOutputStream oos) throws IOException {
    long t1 = System.currentTimeMillis();
    oos.defaultWriteObject();
    if(_bmp!=null){
        int bytes = _bmp.getWidth()*_bmp.getHeight()*4;

        ByteBuffer buffer = ByteBuffer.allocate(bytes); 
        _bmp.copyPixelsToBuffer(buffer);

        byte[] array = buffer.array();      

        oos.writeObject(array);

    }
    Log.v("PaintFX","Elapsed Time: "+(System.currentTimeMillis()-t1));
}

private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException{
    ois.defaultReadObject();
    byte[] data = (byte[]) ois.readObject();
    if(data != null && data.length > 0){
        _bmp = BitmapFactory.decodeByteArray(data, 0, data.length);
    }
}

问题是我得到了

SkImageDecoder :: Factory返回null

那我该怎么办呢.我知道可能的解决方案是将writeObject()更改为

ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
_bmp.compress(Bitmap.CompressFormat.PNG, 100, byteStream);
oos.writeObject(byteStream.toByteArray);

但这种方法慢了近10倍.

• copyPixelsToBuffer~14ms用于写入图像
• _bmp.compress~160ms

更新 发现实际问题是在之后

buffer.array();

所有byte []数组元素都是:0

Answer 1

最后,我找到了一种方法,使其工作,同时更快.使用此方法我遇到两个问题:

1. 我也应该传递Bitmap.Config参数,没有我无法解码字节数组
2. _bmp.compress和_bmp.copyPixelsToBuffer给出不同的数组,所以我不能使用decodeByteArray.

我这样解决了他们

private void writeObject(ObjectOutputStream oos) throws IOException {
    oos.defaultWriteObject();

    if(_bmp!=null){
        int bytes = _bmp.getWidth()*_bmp.getHeight()*4;

        ByteBuffer buffer = ByteBuffer.allocate(bytes);
        _bmp.copyPixelsToBuffer(buffer);

        byte[] array = new byte[bytes]; // looks like this is extraneous memory allocation

        if (buffer.hasArray()) {
            try{
                array = buffer.array();
            } catch (BufferUnderflowException e) {
                e.printStackTrace();
            }
        }

        String configName = _bmp.getConfig().name();

        oos.writeObject(array);
        oos.writeInt(_bmp.getWidth());
        oos.writeInt(_bmp.getHeight());
        oos.writeObject(configName);
    } else {
        oos.writeObject(null);
    }
}

private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException{
    ois.defaultReadObject();

    byte[] data = (byte[]) ois.readObject();
    if (data != null) {
        int w = ois.readInt();
        int h = ois.readInt();
        String configName = (String) ois.readObject();

        Bitmap.Config configBmp = Bitmap.Config.valueOf(configName);
        Bitmap bitmap_tmp = Bitmap.createBitmap(w, h, configBmp);
        ByteBuffer buffer = ByteBuffer.wrap(data);

        bitmap_tmp.copyPixelsFromBuffer(buffer);

        _bmp = bitmap_tmp.copy(configBmp,true);

        bitmap_tmp.recycle();
    } else {
        _bmp = null;
    }
}

这对我来说足够快 - 比bmp.compress方式快15倍.希望这可以帮助 :)