oliver · April 14, 2014 20:28 · Apr 14, 2014
diff --git a/dct-demo.py b/dct-demo.py
@@ -0,0 +1,43 @@
+#!/usr/bin/python
+
+import sys, os
+from PIL import Image
+import numpy
+import scipy.fftpack
+
+sourceImage = sys.argv[1]
+
+image = Image.open(sourceImage)
+image = image.resize( (128,128), 1 )
+image = image.convert("L")
+
+dctSize = image.size[0]
+
+# get raw pixel values:
+pixels = numpy.array(image.getdata(), dtype=numpy.float).reshape((dctSize, dctSize))
+
+# perform 2-dimensional DCT (discrete cosine transform):
+dct = scipy.fftpack.dct(scipy.fftpack.dct(pixels.T, norm="ortho").T, norm="ortho")
+
+# create a series of images with increasingly larger parts of the DCT values being used:
+os.mkdir("frames/")
+for i in range(0, dctSize):
+    dct2 = dct.copy()
+
+    # zero out part of the higher frequencies of the DCT values:
+    dct2[i:,:] = 0
+    dct2[:,i:] = 0
+
+    # perform 2d inverse DCT to get pixels back:
+    idct = scipy.fftpack.idct(scipy.fftpack.idct(dct2.T, norm='ortho').T, norm='ortho')
+
+    # clip/convert pixel values obtained by IDCT, and create image:
+    idct = idct.clip(0, 255)
+    idct = idct.astype("uint8")
+    img = Image.fromarray(idct)
+
+    print img
+    img.save("frames/img_%04d.png" % i)
+
+
+os.system("convert -delay 30 -comment 'example of Discrete Cosine Transform (source image: %s)' frames/img_*.png dct.gif" % sourceImage)