1. Calculate the screen-space AABBs of the two potentially colliding objects. Note that this needs to be done after you've applied all rotations (there are very fast ways of obtaining AABBs from OBBs if you need to). You can represent AABBs in many different ways (e.g. vector2 and two floats - center and extents or two vector2s - bottom left, top right corner). I will assume the second representation - two vector2s for bottom left and top right corner.

   struct AABB { Vector2 bottomLeft; Vector2 topRight; }

2. Do a basic AABB intersection test for an early out.

3. Translate both AABBs to the coordinate space of the first one.

   aabb2.bottomLeft -= aabb1.bottomLeft;
   aabb2.topRight -= aabb1.bottomLeft;
   aabb1.topRight -= aabb1.bottomLeft;
   aabb1.bottomLeft -= aabb1.bottomLeft;

4. As the AABBs are in screen-space they (should) correspond directly to the bitmap representation of your objects on-screen. You get something like:

Now you have to iterate through the red pixels and compare the values from the two images you have. I am assuming you would wish to compare only the alpha values so you would need to mask them out from the ints you get from getPixels(). An example in pseudo C:

int start_x = aabb2.bottomLeft.x;
int start_y = aabb2.topRight.y;
int end_x = aabb1.topRight.x;
int end_y = aabb1.bottomLeft.y;

int ALPHAMASK = 0xFF<<24; // assuming colors are represented as 0xAARRBBGG
Bitmap sprite1;
Bitmap sprite2;

for(int x = start_x; x < end_x; x++) {  
for(int y = start_y; y < end_y; y++) {  
  alpha1 = sprite1.pixels[x+y*sprite1.width] & ALPHAMASK;  
  alpha2 = sprite2.pixels[(x+aabb2.bottomLeft.x)+((y+aabb2.topRight.y)*sprite2.width)] & ALPHAMASK;
  if(alpha1 != 0 && alpha 2 != 0) {
    // pixel is colliding
    return; // you'd probably wish to return after a colliding pixel has been found
  }
}

1. Calculate the screen-space AABBs of the two potentially colliding objects. Note that this needs to be done after you've applied all rotations (there are very fast ways of obtaining AABBs from OBBs if you need to). You can represent AABBs in many different ways (e.g. vector2 and two floats - center and extents or two vector2s - bottom left, top right corner). I will assume the second representation - two vector2s for bottom left and top right corner.

   struct AABB { Vector2 bottomLeft; Vector2 topRight; }

2. Do a basic AABB intersection test for an early out.

3. Translate both AABBs to the coordinate space of the first one.

   aabb2.bottomLeft -= aabb1.bottomLeft;
   aabb2.topRight -= aabb1.bottomLeft;
   aabb1.topRight -= aabb1.bottomLeft;
   aabb1.bottomLeft -= aabb1.bottomLeft;

4. As the AABBs are in screen-space they (should) correspond directly to the bitmap representation of your objects on-screen. You get something like:

Now you have to iterate through the red pixels and compare the values from the two images you have. I am assuming you would wish to compare only the alpha values so you would need to mask them out from the ints you get from getPixels(). An example in pseudo C:

int start_x = aabb2.bottomLeft.x;
int start_y = aabb2.topRight.y;
int end_x = aabb1.topRight.x;
int end_y = aabb1.bottomLeft.y;

int ALPHAMASK = 0xFF<<24; // assuming colors are represented as 0xAARRBBGG
Bitmap sprite1;
Bitmap sprite2;

for(int x = start_x; x < end_x; x++) 
for(int y = start_y; y < end_y; y++) {  
  alpha1 = sprite1.pixels[x+y*sprite1.width] & ALPHAMASK;  
  alpha2 = sprite2.pixels[(x+aabb2.bottomLeft.x)+((y+aabb2.topRight.y)*sprite2.width)] & ALPHAMASK;
  if(alpha1 != 0 && alpha 2 != 0) {
    // pixel is colliding
    return; // you'd probably wish to return after a colliding pixel has been found
  }
}