Question

I wanted to write a simple processing function.

It should run like this:

• Load a Jpeg
• Convert it to Bitmap
• save bitmap as byte array
• process
• data convert back to bitmap show Image.

public class MainActivity extends Activity {

ImageView imgView;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    imgView = (ImageView) findViewById(R.id.imageView1);

    AssetFileDescriptor asf;
    String filename = Environment.getExternalStorageDirectory() + "/Test/"
            + "DSC00751.JPG";
    Bitmap map = BitmapFactory.decodeFile(filename);
    ByteArrayOutputStream bout = new ByteArrayOutputStream();

    // Convert image so it can be stored in byteArray
    map.compress(CompressFormat.JPEG, 100, bout);
    byte[] array = bout.toByteArray();

    // Process image.
    for (int i = 0; i < array.length; i++) {
        if (array[i] < 0) {
            array[i] = (byte) 200;
        }
    }

    // Convert result and display
    Bitmap bmp = BitmapFactory.decodeByteArray(array, 0, array.length);
    imgView.setImageBitmap(bmp);
    Toast.makeText(getApplicationContext(), "done", Toast.LENGTH_SHORT).show();
}

I get a whitescreen in return. No matter how my processing code looks like.
I tried using foreach(byte b : array) before, but this always returned the original image.

What am I doing wrong?

Answer 1

 // Process image.
    for (int i = 0; i < array.length; i++) {
        if (array[i] < 0) {
            array[i] = (byte) 200;
        }
    }

in this code you are changing image bytes!! so thats why it appears white!!
what else?

---

anyway, if you need to process an image you need to do it like that :

    Bitmap bitmap =...;
    int[] pixels = new int[bitmap.getWidth() * bitmap.getHeight()];

    bitmap.getPixels(pixels, 0, bitmap.getWidth(), 0, 0, bitmap.getWidth(), bitmap.getHeight());

now you have the pixels array of the image (int[])