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Apprendre Basic Transformations | Image Processing with OpenCV
Computer Vision Essentials

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Basic Transformations

Reading and Displaying an Image

Before performing transformations, let's first load and display an image using OpenCV. We have already imported the photo. But in your local computer for simple reading and displaying the photo you should use:

Resizing an Image

Resizing is useful for scaling images up or down while maintaining aspect ratio (fx and fy parameters), where fx and fy define the scaling factor for width and height.

You can also specify exact pixel dimensions (dsize parameter), where dsize is (new_y, new_x) output shape.

Rotating an Image

To rotate an image by a specific angle, we use cv2.getRotationMatrix2D() and cv2.warpAffine().

  • cv2.getRotationMatrix2D(center, angle, scale) defines the rotation matrix;

  • cv2.warpAffine(image, matrix, output_size) applies the transformation.

Cropping an Image

Cropping extracts a specific region from an image. It's done using NumPy slicing. The syntax image[start_y:end_y, start_x:end_x] selects a region of interest.

Tâche

Swipe to start coding

You are given an image:

  • Resize image to a (100, 100) shape and store it in resized variable;
  • Extract height and width from image;
  • Calculate center of height and width;
  • Create rotation matrix and stote it in rotation_matrix variable;
  • Rotate image 90 degrees clockwise and stote it in rotated variable;
  • Crop the X: 250-600 and Y: 100-450 region of the image and store in cropped variable.

Solution

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Section 2. Chapitre 1
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book
Basic Transformations

Reading and Displaying an Image

Before performing transformations, let's first load and display an image using OpenCV. We have already imported the photo. But in your local computer for simple reading and displaying the photo you should use:

Resizing an Image

Resizing is useful for scaling images up or down while maintaining aspect ratio (fx and fy parameters), where fx and fy define the scaling factor for width and height.

You can also specify exact pixel dimensions (dsize parameter), where dsize is (new_y, new_x) output shape.

Rotating an Image

To rotate an image by a specific angle, we use cv2.getRotationMatrix2D() and cv2.warpAffine().

  • cv2.getRotationMatrix2D(center, angle, scale) defines the rotation matrix;

  • cv2.warpAffine(image, matrix, output_size) applies the transformation.

Cropping an Image

Cropping extracts a specific region from an image. It's done using NumPy slicing. The syntax image[start_y:end_y, start_x:end_x] selects a region of interest.

Tâche

Swipe to start coding

You are given an image:

  • Resize image to a (100, 100) shape and store it in resized variable;
  • Extract height and width from image;
  • Calculate center of height and width;
  • Create rotation matrix and stote it in rotation_matrix variable;
  • Rotate image 90 degrees clockwise and stote it in rotated variable;
  • Crop the X: 250-600 and Y: 100-450 region of the image and store in cropped variable.

Solution

Switch to desktopPassez à un bureau pour une pratique réelleContinuez d'où vous êtes en utilisant l'une des options ci-dessous
Tout était clair ?

Comment pouvons-nous l'améliorer ?

Merci pour vos commentaires !

Section 2. Chapitre 1
Switch to desktopPassez à un bureau pour une pratique réelleContinuez d'où vous êtes en utilisant l'une des options ci-dessous
Nous sommes désolés de vous informer que quelque chose s'est mal passé. Qu'est-il arrivé ?
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