【Python】Opencv常用函数

港控/mmm° 2022-12-22 04:38 184阅读 0赞

### 文章目录 ###

*  一、图片处理操作
 *   *  1.1 图片尺寸获取
     *  1.2 图片resize
     *  1.3 图片保存
     *  1.4 画矩形
     *  1.5 写文本
 *  二、视频处理操作
 *   *  2.1 视频信息获取
     *  2.2 视频resize及保存

# 一、图片处理操作 #

## 1.1 图片尺寸获取 ##

方法一：opencv

import cv2
    
    img = cv2.imread('my_image.jpg',0)
    height, width = img.shape[:2]

## 1.2 图片resize ##

方法一：opencv

import cv2
    
    frame = cv2.imread('./Pictures/python.png', cv2.IMREAD_UNCHANGED)
    dim = (width, height)
    resized = cv2.resize(frame, dim, interpolation=cv2.INTER_AREA)

参考：[https://www.cnblogs.com/lfri/p/10596530.html][https_www.cnblogs.com_lfri_p_10596530.html]

## 1.3 图片保存 ##

import cv2
    
    cv2.imwrite(output_path, img)

## 1.4 画矩形 ##

cv2.rectangle(img, pt1, pt2, color[, thickness[, lineType[, shift]]])

参数含义

<table> 
 <thead> 
  <tr> 
   <th>参数</th> 
   <th>含义</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>img</td> 
   <td>图片</td> 
  </tr> 
  <tr> 
   <td>pt1</td> 
   <td>矩形的左上角</td> 
  </tr> 
  <tr> 
   <td>pt2</td> 
   <td>矩形的右下角</td> 
  </tr> 
  <tr> 
   <td>color</td> 
   <td>矩形框的颜色，通常使用RGB</td> 
  </tr> 
  <tr> 
   <td>thickness</td> 
   <td>矩形框的线宽；负数或CV_FILLED表示矩形填充</td> 
  </tr> 
  <tr> 
   <td>lineType</td> 
   <td>线的类型：8，4，CV_AA；4 连通 、8 连通、使用高斯滤波器画反锯齿线</td> 
  </tr> 
  <tr> 
   <td>shift</td> 
   <td></td> 
  </tr> 
 </tbody> 
</table>

## 1.5 写文本 ##

cv2.putText(img, text, org, fontFace, fontScale, color[, thickness[, lineType[, bottomLeftOrigin]]])

<table> 
 <thead> 
  <tr> 
   <th>参数</th> 
   <th>含义</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>img</td> 
   <td>图片</td> 
  </tr> 
  <tr> 
   <td>text</td> 
   <td>文本内容</td> 
  </tr> 
  <tr> 
   <td>org</td> 
   <td>文字左下角在图片中的位置</td> 
  </tr> 
  <tr> 
   <td>font</td> 
   <td>字体样式</td> 
  </tr> 
  <tr> 
   <td>fontFace</td> 
   <td>字体格式，FONT_HERSHEY_SIMPLEX, FONT_HERSHEY_PLAIN, FONT_HERSHEY_DUPLEX, FONT_HERSHEY_COMPLEX, FONT_HERSHEY_TRIPLEX, FONT_HERSHEY_COMPLEX_SMALL, FONT_HERSHEY_SCRIPT_SIMPLEX, or FONT_HERSHEY_SCRIPT_COMPLEX</td> 
  </tr> 
  <tr> 
   <td>lineType</td> 
   <td>线的类型：8，4，CV_AA；4 连通 、8 连通、使用高斯滤波器画反锯齿线</td> 
  </tr> 
  <tr> 
   <td>fontScale</td> 
   <td></td> 
  </tr> 
  <tr> 
   <td>color</td> 
   <td>字体颜色</td> 
  </tr> 
  <tr> 
   <td>thickness</td> 
   <td>字体的线宽</td> 
  </tr> 
  <tr> 
   <td>lineType</td> 
   <td>线的类型</td> 
  </tr> 
  <tr> 
   <td>bottomLeftOrigin</td> 
   <td></td> 
  </tr> 
 </tbody> 
</table>

# 二、视频处理操作 #

## 2.1 视频信息获取 ##

import cv2
    
    vcap = cv2.VideoCapture('video.avi') 
    
    if vcap.isOpened(): 
    	# 获取宽、高
        video_width = int(vid.get(cv2.CAP_PROP_FRAME_WIDTH)) 
        video_height = int(vid.get(cv2.CAP_PROP_FRAME_HEIGHT))
        # FourCC
        video_FourCC = int(vid.get(cv2.CAP_PROP_FOURCC))
        # FPS
        video_fps = vid.get(cv2.CAP_PROP_FPS)

## 2.2 视频resize及保存 ##

def resize_video(video_path, output_path, fx=0.5, fy=0.5):
        vid = cv2.VideoCapture(video_path)
        if not vid.isOpened():
            raise IOError("Couldn't open webcam or video")
    
        video_width = int(vid.get(cv2.CAP_PROP_FRAME_WIDTH))
        video_height = int(vid.get(cv2.CAP_PROP_FRAME_HEIGHT))
        video_FourCC = int(vid.get(cv2.CAP_PROP_FOURCC))
        video_fps = vid.get(cv2.CAP_PROP_FPS)
        dim = (int(video_width * fx), int(video_height * fy))
        new_video = cv2.VideoWriter(output_path, video_FourCC, video_fps, dim)
    
        while vid.isOpened():
            is_read, frame = vid.read()
            try:
                resized = cv2.resize(frame, dim, interpolation=cv2.INTER_NEAREST)
                new_video.write(resized)  # 保存视频最后一帧时会莫名报错，所以要使用try。
            except:
                break

[https_www.cnblogs.com_lfri_p_10596530.html]: https://www.cnblogs.com/lfri/p/10596530.html