Question

I’m trying to download a jpg image from the web saving it into a byte array in order to have the compressed image on the ram until I have to show it, but I’m getting a black picture.

What I’m doing is:

URL myFileUrl =null; 

myFileUrl= new URL(fileUrl);

HttpURLConnection conn= (HttpURLConnection)myFileUrl.openConnection();
conn.setDoInput(true);
conn.connect();
conn.setUseCaches(false);

InputStream is = conn.getInputStream();

byte[] ba = new byte[is.available()];

After that I’m keeping the array in the RAM until I have to use it.

To place it, I do:

Bitmap bitmapFromByteArray = BitmapFactory.decodeByteArray(ba,0,ba.length);

imageView1.setImageBitmap(bitmapFromByteArray);

bitmapFromByteArray.recycle();

I solved the problem by doing

URL myFileUrl =null; 

myFileUrl= new URL(fileUrl);

HttpURLConnection conn= (HttpURLConnection)myFileUrl.openConnection();
conn.setDoInput(true);
conn.connect();

InputStream is = conn.getInputStream();

Bitmap bm = BitmapFactory.decodeStream(is);

int size = bm.getWidth() * bm.getHeight();

ByteArrayOutputStream out = new ByteArrayOutputStream(size);
bm.compress(Bitmap.CompressFormat.JPEG, 100, out);

byte[] ba2 = out.toByteArray();
bm.recycle()

Buut by doing this I’m decoding the JPEG and then re-encoding the image multiple times lowering the quality of the picture and using the phone resources longer than necessary. Also, the bitmap I get after re-encoding is bigger than the original jpg image.

Is there any way to get the first method to work?

Thank you.

Answer 1

Are you trying to simply copy the content of an InputStream into a byte array?

You can do this directly with a loop that calls InputStream#read into a byte array, or you can leave the implementation up to others by using IOUtils.toByteArray from Apache commons.

Edit – You don’t need to deal with array initialization if you use the Apache commons method:

byte[] bytes = null;
try {
    bytes = IOUtils.toByteArray(conn.getInputStream());
} catch (IOException e) {
    // handle the exception
}

toByteArray uses a ByteArrayOutputStream to avoid allocating an array up-front, but you wouldn’t need to worry about this.