Opencv 读取的图片是BGR 矩阵：




```python
import cv2 
import matplotlib.pyplot as plt
img=cv2.imread('./res.jpg')
plt.imshow(img)
plt.show()
```

plt显示方法imshow是默认矩阵是RGB的，

![在这里插入图片描述](/static/img/images/00322.png)

想要正确显示，需要：

```python
imgrgb= cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
plt.imshow(imgrgb)
plt.show()
```

![在这里插入图片描述](/static/img/images/00323.png)

Opencv Python 图片通道 BGR 转 RGB imgrgb= cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

读取




```python
import cv2
import numpy as np 
img = cv2.imdecode(np.fromfile("./人物-1.jpg", dtype=np.uint8), 1) # img是矩阵
```

写入：

```python
import cv2
cv2.imencode('.jpg', img)[1].tofile(os.path.join(self.keyword, self.keyword + str(count) + ".jpg"))
```

Python cv2.imread 无法打开中文路径的图像

![在这里插入图片描述](/static/img/images/00362.png)





1 调程序中的127可以提取多少颜色，有时候有毛边；

2 png是带透明度的图，有颜色的部分设置透明度255就是完全不透明，原来白色的部分设置透明度0就是完全透明；

```python
import cv2
import numpy as np
inputimg = 'minio.png'
thresh=180
img1 = cv2.imread(inputimg, 0)
ret, thresh1 = cv2.threshold(img1, 127, 255, cv2.THRESH_BINARY)
img = cv2.imread(inputimg)
b, g, r = cv2.split(img)
b[thresh1 > thresh] = 0
g[thresh1 > thresh] = 0
r[thresh1 > thresh] = 0
alpha_channel = np.zeros(b.shape, dtype=b.dtype)
alpha_channel[thresh1 < thresh] = 255
img = cv2.merge([b, g, r, alpha_channel])
cv2.imwrite("res.png", img)
```

opencv python jpg 转 png 提取icon 提取jpg中有颜色部分

python安装opencv：





> pip install opencv-python

提取视频帧 视频转图片：
```python
import os
mp4file = 'input.mp4'
savefile = "./output"
if not os.path.exists(savefile):
    os.mkdir(savefile)
import cv2
cap = cv2.VideoCapture(mp4file)
fourcc = cv2.VideoWriter_fourcc(*'XVID')
fps = cap.get(cv2.CAP_PROP_FPS)
size = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)), int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))
print(fps)
print(size)
i = 0
while (cap.isOpened()):
    i = i + 1
    ret, frame = cap.read()
    if ret == True:
        cv2.imwrite(savefile + '/' + str(i) + '.jpg', frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    else:
        break
print(i)
cap.release()
cv2.destroyAllWindows()
```

图片转视频：

```python
import os
mp4file = 'out.mp4'
savefile = "./output"
if not os.path.exists(savefile):
    os.mkdir(savefile)
import cv2
fourcc = cv2.VideoWriter_fourcc(*'XVID')
fps = 30
size =(720, 1280)
videoWriter = cv2.VideoWriter(mp4file, fourcc, fps, size)  # 最后一个是保存图片的尺寸
for i in range(1, 1402):
    frame = cv2.imread(savefile + '/' + str(i) + '.jpg')
    videoWriter.write(frame)
videoWriter.release()
```


合成，一定得注意尺寸的大小。

```python
# coding=utf-8
import os
import cv2
from PIL import Image
def makevideo(path, fps):
    """ 将图片合成视频. path: 视频路径，fps: 帧率 """
    fourcc = cv2.VideoWriter_fourcc(*"mp4v")
    path1 = r'D:\yifei111\PycharmProjects\python_test\jigan_res4'
    im = Image.open(r'D:\yifei111\PycharmProjects\python_test\jigan1\251.jpg')
    print(im.size)
    vw = cv2.VideoWriter(path, fourcc, fps, im.size)
    for i in os.listdir(path1):
        frame = cv2.imread(path1 + '\\' + i)
        frame = frame[200:649, :]
        frame = cv2.resize(frame, im.size)
        vw.write(frame)
if __name__ == '__main__':
    video_path = r'D:\yifei111\PycharmProjects\python_test\DST_test_new4.mp4'
    makevideo(video_path, 30)  # 图片转视频
```

python opencv 提取视频帧 视频转图片 图片转视频

[https://www.cnblogs.com/skyfsm/p/7411961.html](https://www.cnblogs.com/skyfsm/p/7411961.html)





看到个有意思的，记录一下。

![在这里插入图片描述](/static/img/images/00558.png)

![在这里插入图片描述](/static/img/images/00559.png)