Resize a large bitmap file to scaled output file on Android

Question

I have a large bitmap (say 3888x2592) in a file. Now, I want to resize that bitmap to 800x533 and save it to another file. I normally would scale the bitmap by calling

Answer 1

I don't know if my solution is best practice, but I achieved loading a bitmap with my desired scaling by using the inDensity and inTargetDensity options. inDensity is 0 initially when not loading a drawable resource, so this approach is for loading non resource images.

The variables imageUri, maxImageSideLength and context are parameters of my method. I posted only the method implementation without the wrapping AsyncTask for clarity.

            ContentResolver resolver = context.getContentResolver();
            InputStream is;
            try {
                is = resolver.openInputStream(imageUri);
            } catch (FileNotFoundException e) {
                Log.e(TAG, "Image not found.", e);
                return null;
            }
            Options opts = new Options();
            opts.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(is, null, opts);

            // scale the image
            float maxSideLength = maxImageSideLength;
            float scaleFactor = Math.min(maxSideLength / opts.outWidth, maxSideLength / opts.outHeight);
            // do not upscale!
            if (scaleFactor < 1) {
                opts.inDensity = 10000;
                opts.inTargetDensity = (int) ((float) opts.inDensity * scaleFactor);
            }
            opts.inJustDecodeBounds = false;

            try {
                is.close();
            } catch (IOException e) {
                // ignore
            }
            try {
                is = resolver.openInputStream(imageUri);
            } catch (FileNotFoundException e) {
                Log.e(TAG, "Image not found.", e);
                return null;
            }
            Bitmap bitmap = BitmapFactory.decodeStream(is, null, opts);
            try {
                is.close();
            } catch (IOException e) {
                // ignore
            }

            return bitmap;