Reduce size of Bitmap to some specified pixel in Android

Question

I would like to reduce My Bitmap image size to maximum of 640px. For example I have Bitmap image of size 1200 x 1200 px .. How can I reduce it to 640px.

Answer 1

Here is working code to reduce Bitmap image resolution (pixels) to desired value...

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;
import android.widget.Toast;

public class ImageProcessActivity extends AppCompatActivity {


    private static final String TAG = "ImageProcessActivity";
    private static final String IMAGE_PATH = "/sdcard/DCIM/my_image.jpg";

    public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {

        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            final int halfHeight = height / 2;
            final int halfWidth = width / 2;

            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) >= reqHeight && (halfWidth / inSampleSize) >= reqWidth) {

                inSampleSize *= 2;
            }
        }

        return inSampleSize;
    }

    public static Bitmap decodeSampleDrawableFromFile(String file, int reqWidth, int reqHeight) {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(file, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeFile(file, options);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_process);

        new AsyncTask() {

            @Override
            protected Bitmap doInBackground(Object... objects) {

                try {

                    return decodeSampleDrawableFromFile(IMAGE_PATH, 640, 640);

                } catch (Exception e) {

                    e.printStackTrace();

                }
                return null;
            }

            @Override
            protected void onPostExecute(Bitmap bitmap) {
                super.onPostExecute(bitmap);

                ((ImageView) findViewById(R.id.img)).setImageBitmap(bitmap);
            }
        }.execute();
    }
}

Steps:

1. Get the Bitmap.Options (image info).

2. Sample the size to desired sample size.

3. Load to Bitmap with given options (desired resolution) from the image file into a bitmap object. But do this operation in a background thread.

4. Load Bitmap image into ImageView on UI thread (onPostExecute()).