Hi everyone,
I'm trying to create an android application that on one of its activities it uploads images from the device to a server.
I'm trying to resize the image's size and sending it to the server.
I found that post Whatsapp like Image Compression in Android with demo and than created these functions.
THese functions compresses the image without a great loss of quality. Similar to WhatsApp's image compression. It returns a string with the filename which can be used in your FileInputStream.

Code:
public String compressImage(String imageUri) {

	String filePath = getRealPathFromURI(imageUri);
	Bitmap scaledBitmap = null;

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

//      by setting this field as true, the actual bitmap pixels are not loaded in the memory. Just the bounds are loaded. If
//      you try the use the bitmap here, you will get null.
	options.inJustDecodeBounds = true;
	Bitmap bmp = BitmapFactory.decodeFile(filePath, options);

	int actualHeight = options.outHeight;
	int actualWidth = options.outWidth;

//      max Height and width values of the compressed image is taken as 816x612

	float maxHeight = 816.0f;
	float maxWidth = 612.0f;
	float imgRatio = actualWidth / actualHeight;
	float maxRatio = maxWidth / maxHeight;

//      width and height values are set maintaining the aspect ratio of the image

	if (actualHeight > maxHeight || actualWidth > maxWidth) {
		if (imgRatio < maxRatio) {
			imgRatio = maxHeight / actualHeight;
			actualWidth = (int) (imgRatio * actualWidth);
			actualHeight = (int) maxHeight;
		} else if (imgRatio > maxRatio) {
			imgRatio = maxWidth / actualWidth;
			actualHeight = (int) (imgRatio * actualHeight);
			actualWidth = (int) maxWidth;
		} else {
			actualHeight = (int) maxHeight;
			actualWidth = (int) maxWidth;

		}
	}

//      setting inSampleSize value allows to load a scaled down version of the original image

	options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);

//      inJustDecodeBounds set to false to load the actual bitmap
	options.inJustDecodeBounds = false;

//      this options allow android to claim the bitmap memory if it runs low on memory
	options.inPurgeable = true;
	options.inInputShareable = true;
	options.inTempStorage = new byte[16 * 1024];

	try {
//          load the bitmap from its path
		bmp = BitmapFactory.decodeFile(filePath, options);
	} catch (OutOfMemoryError exception) {
		exception.printStackTrace();

	}
	try {
		scaledBitmap = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.ARGB_8888);
	} catch (OutOfMemoryError exception) {
		exception.printStackTrace();
	}

	float ratioX = actualWidth / (float) options.outWidth;
	float ratioY = actualHeight / (float) options.outHeight;
	float middleX = actualWidth / 2.0f;
	float middleY = actualHeight / 2.0f;

	Matrix scaleMatrix = new Matrix();
	scaleMatrix.setScale(ratioX, ratioY, middleX, middleY);

	Canvas canvas = new Canvas(scaledBitmap);
	canvas.setMatrix(scaleMatrix);
	canvas.drawBitmap(bmp, middleX - bmp.getWidth() / 2, middleY - bmp.getHeight() / 2, new Paint(Paint.FILTER_BITMAP_FLAG));

//      check the rotation of the image and display it properly
	ExifInterface exif;
	try {
		exif = new ExifInterface(filePath);

		int orientation = exif.getAttributeInt(
				ExifInterface.TAG_ORIENTATION, 0);
		Log.d("EXIF", "Exif: " + orientation);
		Matrix matrix = new Matrix();
		if (orientation == 6) {
			matrix.postRotate(90);
			Log.d("EXIF", "Exif: " + orientation);
		} else if (orientation == 3) {
			matrix.postRotate(180);
			Log.d("EXIF", "Exif: " + orientation);
		} else if (orientation == 8) {
			matrix.postRotate(270);
			Log.d("EXIF", "Exif: " + orientation);
		}
		scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0,
				scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix,
				true);
	} catch (IOException e) {
		e.printStackTrace();
	}

	FileOutputStream out = null;
	String filename = getFilename();
	try {
		out = new FileOutputStream(filename);

//          write the compressed bitmap at the destination specified by filename.
		scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);

	} catch (FileNotFoundException e) {
		e.printStackTrace();
	}

	return filename;

}

public String getFilename() {
	File file = new File(Environment.getExternalStorageDirectory().getPath(), "MyFolder/Images");
	if (!file.exists()) {
		file.mkdirs();
	}
	String uriSting = (file.getAbsolutePath() + "/" + System.currentTimeMillis() + ".jpg");
	return uriSting;
}

private String getRealPathFromURI(String contentURI) {
	Uri contentUri = Uri.parse(contentURI);
	Cursor cursor = getContentResolver().query(contentUri, null, null, null, null);
	if (cursor == null) {
		return contentUri.getPath();
	} else {
		cursor.moveToFirst();
		int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
		return cursor.getString(index);
	}
}

public 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 heightRatio = Math.round((float) height / (float) reqHeight);
		final int widthRatio = Math.round((float) width / (float) reqWidth);
		inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
	}
	final float totalPixels = width * height;
	final float totalReqPixelsCap = reqWidth * reqHeight * 2;
	while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
		inSampleSize++;
	}

	return inSampleSize;
}
I receive an error on the row where it is written: "Cursor cursor = getContentResolver().query(contentUri, null, null, null, null);".
The compiler doesn't recognize the function getContentResolver(). I'm using android studio. How can I run the getContentResolver function?