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Display images on readme #28

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Display images on readme #28

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Display images on readme
farizrahman4u Apr 30, 2017
554bce9
Update README.md
farizrahman4u Apr 30, 2017
9e47e64
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farizrahman4u Apr 30, 2017
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29 changes: 19 additions & 10 deletions README.md
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Expand Up @@ -46,7 +46,8 @@ Instead of manually constructing the translation matrix *M* and calling `cv2.war
translated = imutils.translate(workspace, 25, -75)</pre>

#### Output:
<img src="docs/images/translation.png?raw=true" alt="Translation example"/ style="max-width: 500px;">

<img src="docs/images/translation.png?raw=true" alt="Translation example" style="max-width: 500px;">

## Rotation
Rotating an image in OpenCV is accomplished by making a call to `cv2.getRotationMatrix2D` and `cv2.warpAffine`. Further care has to be taken to supply the *(x, y)*-coordinate of the point the image is to be rotated about. These calculation calls can quickly add up and make your code bulky and less readable. The `rotate` function in `imutils` helps resolve this problem.
Expand All @@ -59,7 +60,8 @@ for angle in xrange(0, 360, 90):
cv2.imshow("Angle=%d" % (angle), rotated)</pre>

#### Output:
<img src="docs/images/rotation.png?raw=true" alt="Rotation example"/ style="max-width: 500px;">

<img src="docs/images/rotation.png?raw=true" alt="Rotation example" style="max-width: 500px;">

## Resizing
Resizing an image in OpenCV is accomplished by calling the `cv2.resize` function. However, special care needs to be taken to ensure that the aspect ratio is maintained. This `resize` function of `imutils` maintains the aspect ratio and provides the keyword arguments `width` and `height` so the image can be resized to the intended width/height while (1) maintaining aspect ratio and (2) ensuring the dimensions of the image do not have to be explicitly computed by the developer.
Expand All @@ -74,7 +76,8 @@ for width in (400, 300, 200, 100):
cv2.imshow("Width=%dpx" % (width), resized)</pre>

#### Output:
<img src="docs/images/resizing.png?raw=true" alt="Resizing example"/ style="max-width: 500px;">

<img src="docs/images/resizing.png?raw=true" alt="Resizing example" style="max-width: 500px;">

## Skeletonization
Skeletonization is the process of constructing the "topological skeleton" of an object in an image, where the object is presumed to be white on a black background. OpenCV does not provide a function to explicitly construct the skeleton, but does provide the morphological and binary functions to do so.
Expand All @@ -90,7 +93,8 @@ skeleton = imutils.skeletonize(gray, size=(3, 3))
cv2.imshow("Skeleton", skeleton)</pre>

#### Output:
<img src="docs/images/skeletonization.png?raw=true" alt="Skeletonization example"/ style="max-width: 500px;">

<img src="docs/images/skeletonization.png?raw=true" alt="Skeletonization example" style="max-width: 500px;">

## Displaying with Matplotlib
In the Python bindings of OpenCV, images are represented as NumPy arrays in BGR order. This works fine when using the `cv2.imshow` function. However, if you intend on using Matplotlib, the `plt.imshow` function assumes the image is in RGB order. A simple call to `cv2.cvtColor` will resolve this problem, or you can use the `opencv2matplotlib` convenience function.
Expand All @@ -106,7 +110,8 @@ plt.imshow(imutils.opencv2matplotlib(cactus))
plt.show()</pre>

#### Output:
<img src="docs/images/matplotlib.png?raw=true" alt="Matplotlib example"/ style="max-width: 500px;">

<img src="docs/images/matplotlib.png?raw=true" alt="Matplotlib example" style="max-width: 500px;">

## URL to Image
This the `url_to_image` function accepts a single parameter: the `url` of the image we want to download and convert to a NumPy array in OpenCV format. This function performs the download in-memory. The `url_to_image` function has been detailed [here](http://www.pyimagesearch.com/2015/03/02/convert-url-to-image-with-python-and-opencv/) on the PyImageSearch blog.
Expand All @@ -118,7 +123,8 @@ cv2.imshow("URL to Image", logo)
cv2.waitKey(0)</pre>

#### Output:
<img src="docs/images/url_to_image.png?raw=true" alt="Matplotlib example"/ style="max-width: 500px;">

<img src="docs/images/url_to_image.png?raw=true" alt="Matplotlib example" style="max-width: 500px;">

## Checking OpenCV Versions
OpenCV 3 has finally been released! But with the major release becomes backward compatibility issues (such as with the `cv2.findContours` and `cv2.normalize` functions). If you want your OpenCV 3 code to be backwards compatible with OpenCV 2.4.X, you'll need to take special care to check which version of OpenCV is currently being used and then take appropriate action. The `is_cv2()` and `is_cv3()` are simple functions that can be used to automatically determine the OpenCV version of the current environment.
Expand All @@ -143,7 +149,8 @@ cv2.imshow("Original", logo)
cv2.imshow("Automatic Edge Map", edgeMap)</pre>

#### Output:
<img src="docs/images/auto_canny.png?raw=true" alt="Matplotlib example"/ style="max-width: 500px;">

<img src="docs/images/auto_canny.png?raw=true" alt="Matplotlib example" style="max-width: 500px;">

## 4-point Perspective Transform
A common task in computer vision and image processing is to perform a 4-point perspective transform of a ROI in an image and obtain a top-down, "birds eye view" of the ROI. The `perspective` module takes care of this for you. A real-world example of applying a 4-point perspective transform can be bound in this blog on on [building a kick-ass mobile document scanner](http://www.pyimagesearch.com/2014/09/01/build-kick-ass-mobile-document-scanner-just-5-minutes/).
Expand All @@ -152,7 +159,8 @@ A common task in computer vision and image processing is to perform a 4-point pe
See the contents of `demos/perspective_transform.py`

#### Output:
<img src="docs/images/perspective_transform.png?raw=true" alt="Matplotlib example"/ style="max-width: 500px;">

<img src="docs/images/perspective_transform.png?raw=true" alt="Matplotlib example" style="max-width: 500px;">

## Sorting Contours
The contours returned from `cv2.findContours` are unsorted. By using the `contours` module the the `sort_contours` function we can sort a list of contours from left-to-right, right-to-left, top-to-bottom, and bottom-to-top, respectively.
Expand All @@ -161,7 +169,8 @@ The contours returned from `cv2.findContours` are unsorted. By using the `contou
See the contents of `demos/sorting_contours.py`

#### Output:
<img src="docs/images/sorting_contours.png?raw=true" alt="Matplotlib example"/ style="max-width: 500px;">

<img src="docs/images/sorting_contours.png?raw=true" alt="Matplotlib example" style="max-width: 500px;">

## (Recursively) Listing Paths to Images
The `paths` sub-module of `imutils` includes a function to recursively find images based on a root directory.
Expand All @@ -179,4 +188,4 @@ for imagePath in paths.list_images("../demo_images"):
../demo_images/notecard.png
../demo_images/pyimagesearch_logo.jpg
../demo_images/shapes.png
../demo_images/workspace.jpg</pre>
../demo_images/workspace.jpg</pre>