Errata for Programming Computer Vision with Python
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The errata list is a list of errors and their corrections that were found after the product was released. If the error was corrected in a later version or reprint the date of the correction will be displayed in the column titled "Date Corrected".
The following errata were submitted by our customers and approved as valid errors by the author or editor.
Color Key: Serious Technical Mistake Minor Technical Mistake Language or formatting error Typo Question Note Update
| Version |
Location |
Description |
Submitted By |
Date Submitted |
Date Corrected |
| Printed |
Page 21
4th line of first source code block |
and example source morphology.py :
the method 'measurements.label()' in :
m = 1*(im < 128l)
labels, numObjects = measurements.label( im )
throws exception "data type not supported" in
c:\Python27\lib\site-packages\scipy\ndimage\measurements.py, 167
im is a matrix of 0's and 1's.
When using the statement
im = ( im < 128 )
the program does work as expected. Here, im is a boolean array containing values True and False.
This same type of array is returned by the line
im = morphology.binary_opening(im, ones((9, 5)), iterations=2)
in the (original) second part of the example.
I am running Windows 7 64bit, python 2.7.3 32-bit, and scipy 0.11.0, numpy 1.6.2 (from the matching binary installer)
Note from the Author or Editor:
On my Mac with OS X 10.8.2, Python 2.7.2 I get the exact same result (45 and 48 objects) for all three versions:
im = 1*(im<128)
im = 1.0*(im<128)
im = (im<128)
Perhaps this is a platform specific problem? I will add note in future versions. |
Frans van der Klip |
Dec 19, 2012 |
|
| Printed, PDF, ePub |
Page 30
Last row of example, bottom of the page. |
The Harris response function code is missing a square of the trace in the denominator.
The line
return Wdet / Wtr
should be
return Wdet / (Wtr*Wtr)
The code online has been updated.
https://github.com/jesolem/PCV
|
Jan Erik Solem
 |
Jan 23, 2013 |
|
| Printed |
Page 40
the center of the code |
matchscores = zeros((desc1_size[0],1),'int')
should be
matchscores = zeros(desc1_size[0],'int')
Note from the Author or Editor:
Both versions work but your suggestion is better. |
aikawa |
Feb 17, 2013 |
|
| Printed |
Page 76
Fourth row from bottom |
The index "j+1" should be "4".
Replace
im1 = array(Image.open(imname[j+1]))
with
im1 = array(Image.open(imname[4]))
|
Jan Erik Solem
|
May 06, 2013 |
|
| Printed |
Page 88
10th line down |
When running code in book, program stops and I get the following error:
box_trans = homography.normalize(dot(H,box_cam1))
ValueError: setting an array element with a sequence.
Runs fine up to this point.
Note from the Author or Editor:
This is indeed a mistake. The line 8 lines down on p87 that reads:
H = homography.H_from_ransac(fp,tp,model)
should read:
H, inliers = homography.H_from_ransac(fp,tp,model)
Updated example code is available on
https://github.com/jesolem/PCV/blob/master/examples/ar_cube.py |
Doug Blanding |
Sep 27, 2012 |
|
| Printed |
Page 91
code |
aspect = (width*fy)/(height*fx)
will truncate the value if the all values are integer.
This should be:
aspect = float(width*fy)/(height*fx)
Note from the Author or Editor:
This could indeed be a problem if someone has integer focal lengths (unlikely). The suggested improvement:
aspect = float(width*fy)/(height*fx)
should be used. |
aikawa |
Feb 17, 2013 |
|
| Printed |
Page 150
code |
import vlfeat as sift
should be
import sift
Note from the Author or Editor:
Yes. The module was called vlfeat but changed name during the book review process. The suggestion
import sift
is correct. |
aikawa |
Feb 23, 2013 |
|
| Printed |
Page 154
code |
The comment says "go through all images", but the code below it loops only the first 100 images.
for i in range(nbr_images)[:100]:
should be
for i in range(nbr_images):
Note from the Author or Editor:
Yes. There is a typo there. The suggested
for i in range(nbr_images):
is correct. |
aikawa |
Mar 13, 2013 |
|
| Printed, PDF, ePub, Mobi, Safari Books Online |
Page 182
Code example at the bottom of the page |
The tiny helper function convert_labels is missing from this example.
def convert_labels(labels,transl):
""" Convert between strings and numbers. """
return [transl[l] for l in labels]
|
Jan Erik Solem
|
Feb 10, 2013 |
|
| Printed |
Page 212,213
P212: at the end of the first code; P213: at the end of the code |
Bothe codes teriminated normally when run on the MSDOS command line. However they can not terminated when run in IDLE(Python GUI) and PyScripter.
Adding the following function at the end of the code can solve this problem for most of platform.
cv2.destroyAllWindows()
Note from the Author or Editor:
Thanks. A comment should be added in future versions of the text. |
ColorRGB |
Feb 28, 2013 |
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