Go through every pixel of an image and then dispose of it
I think your Bitmap property shouldn't have a setter. If you use it, you don't dispose the old Bitmap and you don't reset size. Both seem to be erroneous to me.



public Bitmap Bitmap
{
    get { return (source); }
    set { source = value; }
}


Why is source in parentheses?

Also, this could be an auto-property. You would then use the (possibly private) setter instead of the field in the constructor.



catch(Exception)
{
    throw;
}


This doesn't do anything, get rid of it.



public BGRA* this[int x, int y]
{
    get
    {
        return (BGRA*)(baseLine + y * width + x * sizeof(BGRA));
    }
}


If the type of baseLine was BGRA* (and you also changed width not to include the size), then the return statement could be simplified to:

return &amp;baseLine[y * width + x];


Also, I would consider returning BGRA directly, I think that's more natural (assuming doing that doesn't decrease performance noticeably).