opencv - 裁剪图片并填充为正方形

[ooolky]

python

• 参考
  • Image Resizing using OpenCV
  • How to Resize, Pad Image to Square Shape and Keep Its Aspect Ratio in Python

• 步骤

  import cv2
  import os
  
  def resize(im, size):
  
      desired_size = size
      old_size = im.shape[:2] # old_size is in (height, width) format
  
      ratio = float(desired_size)/max(old_size)
      new_size = tuple([int(x*ratio) for x in old_size])
  
      # new_size should be in (width, height) format
  
      im = cv2.resize(im, (new_size[1], new_size[0]))
  
      delta_w = desired_size - new_size[1]
      delta_h = desired_size - new_size[0]
      top, bottom = delta_h//2, delta_h-(delta_h//2)
      left, right = delta_w//2, delta_w-(delta_w//2)
  
      color = [0, 0, 0]
      new_im = cv2.copyMakeBorder(im, top, bottom, left, right, cv2.BORDER_CONSTANT,
          value=color)
  
      return new_im
  
  folder = "./"
  images = []
  size = 640
  crop = 6
  for filename in os.listdir(folder):
      img = cv2.imread(os.path.join(folder,filename))
      if img is not None:
          width = img.shape[1]
          height =img.shape[0]
  
          #crop
          img = img[0:height, int(width/crop):width - int(width/crop)]
  
          #resize
          img = resize(img, size)
  
          cv2.imwrite(folder + filename,img)

[ooolky]

c++

• 参考
  • How to crop a CvMat in OpenCV
  • Resize an image to a square but keep aspect ratio c++ opencv

• 步骤

  cv::Mat GetSquareImage(const cv::Mat& img_origin, int target_width = 640)
  {
      int width = img_origin.cols,
          height = img_origin.rows,
          crop = 6;
  
      //crop
      cv::Mat img = img_origin(cv::Rect(width / crop, 0, width - width / crop, height));
  
      //resize
      cv::Mat square = cv::Mat::zeros(target_width, target_width, img.type());
  
      int max_dim = (width >= height) ? width : height;
      float scale = ((float)target_width) / max_dim;
      cv::Rect roi;
      if (width >= height)
      {
          roi.width = target_width;
          roi.x = 0;
          roi.height = height * scale;
          roi.y = (target_width - roi.height) / 2;
      }
      else
      {
          roi.y = 0;
          roi.height = target_width;
          roi.width = width * scale;
          roi.x = (target_width - roi.width) / 2;
      }
  
      cv::resize(img, square(roi), roi.size());
  
      return square;
  }