when png images are uploaded from twitter mobile appp the resultant image is not png android

when i upload a PNG image on twitter from web browser and try to download the the same image i get the PNG image only but when i upload it from twitter mobile app the resultant image is a jpeg image. please help me to resolve the issue since image quality deteriorates a lot.

output = new FileOutputStream(file);
            // Compress into png format image from 0% - 100%
            newBitmap.compress(Bitmap.CompressFormat.PNG, 100, output);
            output.flush();
            output.close();