Data commit

Task/Bitmap-Read-a-PPM-file/Python/bitmap-read-a-ppm-file.py

@@ -0,0 +1,69 @@
+# With help from http://netpbm.sourceforge.net/doc/ppm.html
+
+# String masquerading as ppm file (version P3)
+import io
+
+ppmtxt = '''P3
+# feep.ppm
+4 4
+15
+ 0  0  0    0  0  0    0  0  0   15  0 15
+ 0  0  0    0 15  7    0  0  0    0  0  0
+ 0  0  0    0  0  0    0 15  7    0  0  0
+15  0 15    0  0  0    0  0  0    0  0  0
+'''
+
+
+def tokenize(f):
+    for line in f:
+        if line[0] != '#':
+            for t in line.split():
+                yield t
+
+def ppmp3tobitmap(f):
+    t = tokenize(f)
+    nexttoken = lambda : next(t)
+    assert 'P3' == nexttoken(), 'Wrong filetype'
+    width, height, maxval = (int(nexttoken()) for i in range(3))
+    bitmap = Bitmap(width, height, Colour(0, 0, 0))
+    for h in range(height-1, -1, -1):
+        for w in range(0, width):
+            bitmap.set(w, h, Colour( *(int(nexttoken()) for i in range(3))))
+
+    return bitmap
+
+print('Original Colour PPM file')
+print(ppmtxt)
+ppmfile = io.StringIO(ppmtxt)
+bitmap = ppmp3tobitmap(ppmfile)
+print('Grey PPM:')
+bitmap.togreyscale()
+ppmfileout = io.StringIO('')
+bitmap.writeppmp3(ppmfileout)
+print(ppmfileout.getvalue())
+
+
+'''
+The print statements above produce the following output:
+
+Original Colour PPM file
+P3
+# feep.ppm
+4 4
+15
+ 0  0  0    0  0  0    0  0  0   15  0 15
+ 0  0  0    0 15  7    0  0  0    0  0  0
+ 0  0  0    0  0  0    0 15  7    0  0  0
+15  0 15    0  0  0    0  0  0    0  0  0
+
+Grey PPM:
+P3
+# generated from Bitmap.writeppmp3
+4 4
+11
+    0  0  0    0  0  0    0  0  0    4  4  4
+    0  0  0   11 11 11    0  0  0    0  0  0
+    0  0  0    0  0  0   11 11 11    0  0  0
+    4  4  4    0  0  0    0  0  0    0  0  0
+
+'''