OpenCV is an open source library for computer vision and machine learning. It contains many image processing functions, including cropping pictures. In Python, we can use OpenCV’s `cv2` module to achieve image cropping.
The following are the detailed steps to crop images using OpenCV:
1. Import the required libraries:
```python
import cv2
```
2. Read the image:
```python
image = cv2.imread('path/to/your/ image.jpg')
```
3. Get the width and height of the image:
```python
height, width, _ = image.shape
```
4. Define the cropping area:
```python
start_row, start_col = int(height * 0.25), int(width * 0.25)
end_row, end_col = int(height * 0.75), int(width * 0.75)
```
Here, we set the upper left corner and lower right corner of the image to 1/4 of the original image and 3/4. You can adjust these values as needed.
5. Crop the image:
```python
cropped_image = image[start_row:end_row, start_col:end_col]
```
6. Display the cropped image:
```python
cv2.imshow('Cropped Image', cropped_image)
cv2.waitKey(0)
cv2.destroyAllWindows()
````
7. Save the cropped image:
`` `python
cv2.imwrite('path/to/save/cropped_image.jpg', cropped_image)
```
Integrating the above codes together, you can get a complete program for cropping images:
```python
import cv2
# Read Image
image = cv2.imread('path/to/your/image.jpg')
# Get the width and height of the image
height, width, _ = image.shape
# Define the cropping area
start_row, start_col = int(height * 0.25), int(width * 0.25)
end_row, end_col = int(height * 0.75), int(width * 0.75)
# Cropped image
cropped_image = image[start_row:end_row, start_col:end_col]
# Display the cropped image
cv2.imshow('Cropped Image', cropped_image)
cv2.waitKey(0)
cv2.destroyAllWindows()
# Save the cropped image
cv2.imwrite('path/to/save/cropped_image.jpg', cropped_image)
```
This is how to crop an image using OpenCV. Hope this helps!
The following are several commonly used OpenCV codes for cropping images:
1. Crop the image in the specified area```python import cv2
# Read the image img = cv2.imread('image.jpg') # Specify the cropping area x, y, w, h = 100, 100, 200, 200 # Crop Image crop_img = img[y:y+h, x:x+w] # Display the cropped image cv2.imshow('crop_img', crop_img) cv2.waitKey(0) cv2.destroyAllWindows() ```` 2. According to Proportionally crop the image```python import cv2 # Read the image img = cv2.imread('image.jpg') # Get the image size height, width = img.shape[:2] # Specify the cropping ratio scale = 0.5 # Calculate cropping Area x, y, w, h = int(width*(1-scale)/2), int(height*(1-scale)/2), int(width*scale), int(height*scale) # Cropping Image crop_img = img[y:y+h, x:x+w]
# Display the cropped image
cv2.imshow('crop_img', crop_img)
cv2.waitKey(0)
cv2.destroyAllWindows()
````
3. Crop the image according to the target size
```python
import cv2
# Read the image
img = cv2 .imread('image.jpg')
# Specify the target size
target_width, target_height = 200, 200
# Adjust the image size
resized_img = cv2.resize(img, (target_width, target_height))
# Display the adjusted image
cv2.imshow('resized_img ', resized_img)
cv2.waitKey(0)
cv2.destroyAllWindows()
```