Abstracted out these fixtures.

glymur/test/fixtures.py

@@ -0,0 +1,93 @@
+import re
+import sys
+
+import numpy as np
+
+def mse(A, B):
+    """Mean Square Error"""
+    diff = A.astype(np.double) - B.astype(np.double)
+    #e = np.sqrt(np.mean(diff**2))
+    e = np.mean(diff**2)
+    return e
+
+
+def peak_tolerance(A, B):
+    """Peak Tolerance"""
+    diff = np.abs(A.astype(np.double) - B.astype(np.double))
+    p = diff.max()
+    return p
+
+
+def read_pgx(pgx_file):
+    """Helper function for reading the PGX comparison files.
+
+    Open the file in ascii mode and read the header line.
+    Will look something like
+
+    PG ML + 8 128 128
+    PG%[ \t]%c%c%[ \t+-]%d%[ \t]%d%[ \t]%d"
+    """
+    header = ''
+    with open(pgx_file, 'rb') as fp:
+        while True:
+            x = fp.read(1)
+            if x[0] == 10 or x == '\n':
+                pos = fp.tell()
+                break
+            else:
+                if sys.hexversion < 0x03000000:
+                    header += x
+                else:
+                    header += chr(x[0])
+
+    header = header.rstrip()
+    n = re.split('\s', header)
+
+    if (n[1][0] == 'M') and (sys.byteorder == 'little'):
+        swapbytes = True
+    elif (n[1][0] == 'L') and (sys.byteorder == 'big'):
+        swapbytes = True
+    else:
+        swapbytes = False
+
+    if (len(n) == 6):
+        bitdepth = int(n[3])
+        signed = bitdepth < 0
+        if signed:
+            bitdepth = -1 * bitdepth
+        nrows = int(n[5])
+        ncols = int(n[4])
+    else:
+        bitdepth = int(n[2])
+        signed = bitdepth < 0
+        if signed:
+            bitdepth = -1 * bitdepth
+        nrows = int(n[4])
+        ncols = int(n[3])
+
+    if signed:
+        if bitdepth <= 8:
+            dtype = np.int8
+        elif bitdepth <= 16:
+            dtype = np.int16
+        else:
+            raise RuntimeError("unhandled bitdepth")
+    else:
+        if bitdepth <= 8:
+            dtype = np.uint8
+        elif bitdepth <= 16:
+            dtype = np.uint16
+        else:
+            raise RuntimeError("unhandled bitdepth")
+
+    shape = [nrows, ncols]
+
+    # Reopen the file in binary mode and seek to the start of the binary
+    # data
+    with open(pgx_file, 'rb') as fp:
+        fp.seek(pos)
+        data = np.fromfile(file=fp, dtype=dtype).reshape(shape)
+
+    return(data.byteswap(swapbytes))
+
+