Q:

Saving JPEG files in Android with no loss of pixel information

I'm loading a jpeg-file via BitmapFactory and try to save it again (later I want to do some calculation on the pixel data before I save it again).
But if I try to save it with
FileOutputStream fos = new FileOutputStream(new File("/sdcard/test.jpg"));
originalImage.compress(Bitmap.CompressFormat.JPEG, 100, fos);

then it is not exactly the same result as in the original picture. Some pixel have got different color values and this ist not useful for my later calculation.
Is there a possibility to safe it lossless? Or is the problem already when I load the picture with 
Bitmap originalImage = BitmapFactory.decodeFile("/sdcard/input.jpg");

few lines before?

A:

Is there a possibility to safe it lossless?

No. The JPEG format uses a lossy compression. It makes no formal guarantees even if you set the quality to 100.

Or is the problem already when I load the picture with [...]

No, bitmaps are... maps of bits, i.e. they represent the exact bits of the image data.

