BitmapFactory.decodeStream returning null when options are set.

Question

Hi!

I'm having issues with BitmapFactory.decodeStream(inputStream). When using it without options, it will return an image. But when I use it with options as in .decodeStream(inputStream, null, options) it never returns Bitmaps.

What I'm trying to do is to downsample a Bitmap before I actually load it to save memory. I've read some good guides, but none using .decodeStream.

Here

And here

And here

WORKS JUST FINE

URL url = new URL(sUrl);
HttpURLConnection connection  = (HttpURLConnection) url.openConnection();

InputStream is = connection.getInputStream();
Bitmap img = BitmapFactory.decodeStream(is, null, options);   

DOESNT WORK

InputStream is = connection.getInputStream();
Bitmap img = BitmapFactory.decodeStream(is, null, options);  

InputStream is = connection.getInputStream();    

Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;

BitmapFactory.decodeStream(is, null, options);

Boolean scaleByHeight = Math.abs(options.outHeight - TARGET_HEIGHT) >= Math.abs(options.outWidth - TARGET_WIDTH);

if(options.outHeight * options.outWidth * 2 >= 200*100*2){
// Load, scaling to smallest power of 2 that'll get it <= desired dimensions
    double sampleSize = scaleByHeight
    ? options.outHeight / TARGET_HEIGHT
    : options.outWidth / TARGET_WIDTH;
    options.inSampleSize = 
        (int)Math.pow(2d, Math.floor(
        Math.log(sampleSize)/Math.log(2d)));
}

  // Do the actual decoding
  options.inJustDecodeBounds = false;
  Bitmap img = BitmapFactory.decodeStream(is, null, options);

Answer 1

I think the problem is with the "calculate-scale-factor" logic because rest of the code looks correct to me (assuming of course that inputstream is not null).

It would be better if you can factor out all the size calculation logic from this routine into a method(call it calculateScaleFactor() or whatever) and test that method independently first.

Something like:

// Get the stream 
InputStream is = mUrl.openStream();

// get the Image bounds
BitmapFactory.Options options=new BitmapFactory.Options(); 
options.inJustDecodeBounds = true;

bitmap = BitmapFactory.decodeStream(is,null,options);

//get actual width x height of the image and calculate the scale factor
options.inSampleSize = getScaleFactor(options.outWidth,options.outHeight,
                view.getWidth(),view.getHeight());

options.inJustDecodeBounds = false;
bitmap=BitmapFactory.decodeStream(mUrl.openStream(),null,options);

and test getScaleFactor(...) independently.

It will also help to surround the entire code with try..catch{} block, if not done already.

Answer 2

The problem was that once you've used an InputStream from a HttpUrlConnection, you can't rewind and use the same InputStream again. Therefore you have to create a new InputStream for the actual sampling of the image.

  Options options = new BitmapFactory.Options();
  options.inJustDecodeBounds = true;

  BitmapFactory.decodeStream(is, null, options);

  Boolean scaleByHeight = Math.abs(options.outHeight - TARGET_HEIGHT) >= Math.abs(options.outWidth - TARGET_WIDTH);

  if(options.outHeight * options.outWidth * 2 >= 200*200*2){
         // Load, scaling to smallest power of 2 that'll get it <= desired dimensions
        double sampleSize = scaleByHeight
              ? options.outHeight / TARGET_HEIGHT
              : options.outWidth / TARGET_WIDTH;
        options.inSampleSize = 
              (int)Math.pow(2d, Math.floor(
              Math.log(sampleSize)/Math.log(2d)));
     }

        // Do the actual decoding
        options.inJustDecodeBounds = false;

        is.close();
        is = getHTTPConnectionInputStream(sUrl);
        Bitmap img = BitmapFactory.decodeStream(is, null, options);
        is.close();