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Add pad_output argmument to match_template.

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Tony S Yu
2012-05-08 21:32:06 -04:00
parent 3c7ae849b9
commit cbdea0d36e
1 changed files with 23 additions and 8 deletions
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skimage/feature/template.py
+23 -8
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@@ -6,7 +6,7 @@ import _template
from skimage.util.dtype import _convert from skimage.util.dtype import _convert
def match_template(image, template, method='norm-coeff'): def match_template(image, template, method='norm-coeff', pad_output=True):
"""Finds a template in an image using normalized correlation. """Finds a template in an image using normalized correlation.
TODO: The output is currently smaller than the input image due to TODO: The output is currently smaller than the input image due to
@@ -14,11 +14,11 @@ def match_template(image, template, method='norm-coeff'):
Parameters Parameters
---------- ----------
image : array_like, dtype=float image : array_like
Image to process. Image to process.
template : array_like, dtype=float template : array_like
Template to locate. Template to locate.
method: str (default 'norm-coeff') method : str
The correlation method used in scanning. The correlation method used in scanning.
T represents the template, I the image and R the result. T represents the template, I the image and R the result.
The summation is done over X = 0..w-1 and Y = 0..h-1 of the template. The summation is done over X = 0..w-1 and Y = 0..h-1 of the template.
@@ -32,17 +32,32 @@ def match_template(image, template, method='norm-coeff'):
T'(x, y) = T(X, Y) - 1/(w * h) * Sum(X',Y')[T(X', Y')] T'(x, y) = T(X, Y) - 1/(w * h) * Sum(X',Y')[T(X', Y')]
I'(x + X, y + Y) = I(x + X, y + Y) I'(x + X, y + Y) = I(x + X, y + Y)
- 1/(w * h) * Sum(X',Y')[I(x + X', y + Y')] - 1/(w * h) * Sum(X',Y')[I(x + X', y + Y')]
pad_output : bool
If True, pad output array to be the same size as the input image.
Otherwise, the output is an array with shape `(M - m + 1, N - n + 1)`
for an `(M, N)` image and an `(m, n)` template.
Returns Returns
------- -------
output : ndarray, dtype=float output : ndarray
Correlation results between 0.0 and 1.0, maximum indicating the most Correlation results between 0.0 and 1.0, which correspond to the match
probable match. probability when the template's *origin* (i.e. its top-left corner) is
placed at that position. The bottom and right edges of `output` are
truncated (`pad_output = False`) or zero-padded (`pad_output = True`),
since otherwise the template would extend beyond the image edges.
""" """
if method not in ('norm-corr', 'norm-coeff'): if method not in ('norm-corr', 'norm-coeff'):
raise ValueError("Unknown template method: %s" % method) raise ValueError("Unknown template method: %s" % method)
image = _convert(image, np.float32) image = _convert(image, np.float32)
template = _convert(template, np.float32) template = _convert(template, np.float32)
return _template.match_template(image, template, method) result = _template.match_template(image, template, method)
if pad_output:
h, w = result.shape
full_result = np.zeros(image.shape, dtype=np.float32)
full_result[:h, :w] = result
return full_result
else:
return result