Resize and Crop

Code

import cv2

img = cv2.imread("input.jpg")
h, w = img.shape[:2]

# Resize to fixed size
fixed = cv2.resize(img, (300, 200))

# Resize by scale factor, preserving aspect
scaled = cv2.resize(img, None, fx=0.5, fy=0.5,
                    interpolation=cv2.INTER_AREA)

# Crop a region of interest (y, x ordering)
roi = img[100:400, 200:600]

# Resize to a target width keeping aspect ratio
target_w = 400
ratio = target_w / w
new_size = (target_w, int(h * ratio))
resized = cv2.resize(img, new_size, interpolation=cv2.INTER_LINEAR)

cv2.imwrite("roi.jpg", roi)

Explanation

resize() accepts either an explicit (width, height) or scale factors fx and fy, with INTER_AREA best for shrinking and INTER_CUBIC for enlarging. Cropping uses NumPy slicing with row-first indexing [y1:y2, x1:x2]. Aspect ratio can be preserved by computing the new height from a target width.

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