#!/usr/bin/env python

'''
GIMP plugin that generates a Gaussian pyramid.

A Gaussian pyramid is a sequence of images where each is down-sampled
(smaller dimensions in pixels, i.e. resolution) from previous image.
Loosely speaking, each is blurred from the previous,
but blur depends on the resolution of the display device and size image is displayed.

This is a brute force method.
There an elegant and much faster (but harder to program) algorithm, using the "gaussian reduce operator."
'''

from gimpfu import *


class GaussianPyramid(list):
  ''' 
  List of images which is a Gaussian pyramid.
  
  Behaves as a list.  Images generated at init.
  
  Image at subscript [0] is original image.
  Each image contains a scaled selection mask like the original.
  Hardcoded to scale by half.
  
  Boundary conditions: downsample an image to one pixel in the smallest dimension.
  '''
  
  def __init__(self, image, smallestImageDimension):
    ''' Generate '''
    assert image.width > 1 and image.height > 1 # Can't downsample smaller image
    assert smallestImageDimension >= 1 # Top result image larger than zero pixel 
    
    super(GaussianPyramid,self).append(image)
    
    prevImage = image
    # Stop when width or height of top of pyramid is smaller than desired
    while prevImage.width/2 >= smallestImageDimension and prevImage.height/2 >= smallestImageDimension:
      newImage = pdb.gimp_image_duplicate(prevImage)
      pdb.gimp_image_scale_full(newImage, prevImage.width/2, prevImage.height/2, 2) # 2=cubic filter
      super(GaussianPyramid,self).append(newImage)
      prevImage = newImage

    
    
    
def generateAndDisplayPyramid(img, drawable, smallestImageDimension ):
  
  pyramid = GaussianPyramid(img, smallestImageDimension)
  
  # open display for each image in pyramid except the original
  for image in pyramid[1:]:
    displayID = pdb.gimp_display_new(image)
  
  pdb.gimp_displays_flush() # displays become visible



register(
        "python_fu_gaussian_pyramid",
        "Generate a gaussian pyramid of images.",
        "Creates a sequence of smaller images.",
        "Lloyd Konneker",
        "Copyright 2012 Lloyd Konneker",
        "2012",
        "<Image>/Filters/Render/Gaussian pyramid...",
        "RGB*, GRAY*",
        [
           (PF_SPINNER, "smallestImageDimension", "Dimension of smallest image (pixels):", 2, (1, 100, 1) )
        ],
        [],
        generateAndDisplayPyramid)

if __name__== '__main__' :
  main()