Question

I need to send a PNG to a server. One very simple solution would be to create a Bitmap and convert it to a byte[] with the following code:

final Bitmap bitmap = BitmapFactory.decodeResource(res, R.drawable.some_image);
final ByteArrayOutputStream os = new ByteArrayOutputStream();
bitmap.compress(CompressFormat.PNG, 100, os);
final byte[] data = os.toByteArray();

Since I want to save time and memory I would like to achieve this without the need of creating a Bitmap.

One idea would be to access the Drawable as a File but I don’t know how to get the correct path.

Any ideas?

Answer 1

harism gave me the final hint: use one of the Resoureces.openRawResource methods.

Here is my final solution:

private byte[] fetchImageData(Resources res) throws IOException {
    final AssetFileDescriptor raw = res.openRawResourceFd(R.drawable.some_image);
    final FileInputStream is = raw.createInputStream();

    // there are plenty of libraries around to achieve this with just one line...
    final ByteArrayOutputStream buffer = new ByteArrayOutputStream();

    int nRead;
    final byte[] data = new byte[16384];

    while ((nRead = is.read(data, 0, data.length)) != -1) {
        buffer.write(data, 0, nRead);
    }

    buffer.flush();

    return buffer.toByteArray();
}

In my case I had an PNG of 250×200 px and a file size of 42046 Byte. The Bitmap approach needs around 500ms and the raw approach 3ms.

Hope someone can use this solution.