What you're trying to do sounds rather easy, you just need to do a few things to make it all come together. Here's just one possibility:

Scale down a duplicate of your travelling bitmap when it is first being loaded. Use a routine to check for opaque pixels or pixels of a certain range of color to determine the irregular shape within the image, then store the results as an array of points (do this only once, at load time.) Scale the coordinates of these points back up to normal resolution and transform them along with the image each frame.

Finally, draw line segments between the current location of each point and the next expected location of each point. Use the same principle to create line segments in collidable surfaces, etc. If any of the projected lines of travel intersect with a surface line segment, objects have collided.

Does that make any sense?