Loading only part of a bitmap file in Android

Question

I would like to load a cropped version of a bitmap image into a Bitmap object, without loading the original bitmap as well.

Is this at all possible without writing c

Answer 1

@RKN

Your method can also throw OutOfMemoryError exception - if cropped bitmap exceeds VM.

My method combines Yours and protection against this exeption: (l, t, r, b - % of image)

    Bitmap cropBitmap(ContentResolver cr, String file, float l, float t, float r, float b)
{
    try 
    {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;

        // First decode with inJustDecodeBounds=true to check dimensions
        BitmapFactory.decodeFile(file, options);
        int oWidth = options.outWidth;
        int oHeight = options.outHeight;

        InputStream istream = cr.openInputStream(Uri.fromFile(new File(file)));

        BitmapRegionDecoder decoder = BitmapRegionDecoder.newInstance(istream, false);
        if (decoder != null)
        {
            options = new BitmapFactory.Options();

            int startingSize = 1;
            if ((r - l) * oWidth * (b - t) * oHeight > 2073600)
                startingSize = (int) ((r - l) * oWidth * (b - t) * oHeight / 2073600) + 1;

            for (options.inSampleSize = startingSize; options.inSampleSize <= 32; options.inSampleSize++)
            {
                try
                {
                    return decoder.decodeRegion(new Rect((int) (l * oWidth), (int) (t * oHeight), (int) (r * oWidth), (int) (b * oHeight)), options);    
                }
                catch (OutOfMemoryError e)
                {
                    Continue with for loop if OutOfMemoryError occurs
                }
            }
        }
        else
            return null;
    }
    catch (FileNotFoundException e)
    {
        e.printStackTrace();
    }
    catch (IOException e) 
    {
        e.printStackTrace();
    }

    return null;
}

and returns max available bitmap or null