'''MakeReductions.py
Copy a folder tree containing .JPG image files, making reduced-resolution
copies of the images found, and naming the new folders slightly differently.

SF is the scale factor for reduction. The default given is: SF = 0.1
'''

SF = 0.1    # scale factor
RF = 1.0/SF # resampling factor
import os   # operating system functions

def list_JPGs(folder):
  files = os.listdir(folder)
  return filter(lambda f: f[-4:]==".JPG", files)

def list_folders(folder):
  files = os.listdir(folder)
  return filter(\
    lambda f: os.path.isdir(os.path.join(folder,f)),
    files)

def reduce_image(source_path, destination_path): 
  print "Preparing to  reduce the image: "+\
        source_path+" to get: "+destination_path
  pmOpenImage(1, source_path)
  width = pmGetImageWidth(1)
  height = pmGetImageHeight(1)
  w1 = int(SF*width)
  h1 = int(SF*height)
  pmSetSource1(1)
  newWin = pmNewImage(2, destination_path, w1, h1, 255, 0, 0)
  pmSetDestination(newWin)
  pmSetFormula("S1("+str(RF)+"*x,"+str(RF)+"*y)")
  pmCompute()
  pmSaveImageAs(newWin, destination_path)

def reduce_all_in_folder_tree(source_path,
                              source_folder_name,
                              destination_path):
  # create destination folder.
  new_destination_path =\
    os.path.join(destination_path,
                 source_folder_name+"_reduced_by_"+str(SF))
  print "new_destination_path = "+new_destination_path
  os.makedirs(new_destination_path)
  # go into the source folder and reduce all the JPGs there.
  new_source_path = os.path.join(source_path, source_folder_name)
  print "new_source_path = "+new_source_path
  JPGs = list_JPGs(new_source_path)
  for fn in JPGs:
    new_fn = fn[:-4]+"_reduced_by_"+str(SF)+".JPG"
    reduce_image(os.path.join(new_source_path, fn),
                 os.path.join(new_destination_path, new_fn))
  # Process subdirectories recursively:
  print "Requesting list of folders in "+new_source_path
  folders = list_folders(new_source_path)
  print "Folders to be processed: "+str(folders)
  for f in folders:
    # Now here is the recursive call, made once per subfolder:
    reduce_all_in_folder_tree(new_source_path, f, new_destination_path)

# Now let's initiate the whole operation:
reduce_all_in_folder_tree('.', 'My-Images', '.')