# Python學習筆記 0004 (在輸出視窗畫線、圓、文字、調整顏色)
## 抓取(Cropped)

import cv2
frameWidth = 400
frameHeight = 400
img = cv2.imread("img7.jpg")
img = cv2.resize(img, (frameWidth, frameHeight))
imgCropped = img[0:270,100:380]
cv2.imshow("img", img)
cv2.imshow("Cro", imgCropped)
cv2.waitKey(0)

![Uploading file..._uvi9rj790]()

- img[0:270,100:380]
0,0是在最左上角
0:270左上往下數270pixel

- 100:380是
100是最左上往右數100pixel
380是最左上往右數380pixel

## 外框shape

import cv2
frameWidth = 300
frameHeight = 400
img = cv2.imread("img7.jpg")
img = cv2.resize(img, (300, 400))

imgCropped = img[0:270, 100:280]
imgCroResize = cv2.resize(imgCropped, (img.shape[0],img.shape[1]))

print(img.shape)
print(imgCropped.shape)
print(imgCroResize.shape)

cv2.imshow("img", img)
cv2.imshow("Cro", imgCropped)
cv2.imshow("CroRe", imgCroResize) 

![Uploading file..._j89pv7vya]()

- print out

(400, 300, 3)
(270, 180, 3)
(300, 400, 3)

imgCropped抓取img後、再被放入imgCroResize
imgCroResize的外框的資料(frameWidth, frameHeight)
抓取(400, 300, 3)
shape[0]=400
shape[1]=300
(imgCropped, (img.shape[0],img.shape[1])=(imgCropped, (400,300)

- 程式碼 跟 印出的shape的 寬高順位不同
程式碼(300, 400) 寬300 高400
印出shape(400, 300) 高400 寬300

- (400, 300, 3)的3是?
3是代表RGB的意思

### 例子1

import cv2
import numpy as np

img1 = np.zeros((2, 2, 3))
print(img1)
print(img1.shape)

cv2.imshow("img", img1)
cv2.waitKey(0)

- 輸出

[[[0. 0. 0.]
[0. 0. 0.]]

[[0. 0. 0.]
[0. 0. 0.]]]
(2, 2, 3)

- [0. 0. 0.]那個點代表浮點數

由於我們不要小數點要整數(integer)
所以用uint8
- img1 = np.zeros((2, 2, 3))
2,2表示長寬為2

### 例子2

import cv2
import numpy as np

img1 = np.zeros((2, 2, 3), np.uint8)
print(img1)
print(img1.shape)

cv2.imshow("img", img1)
cv2.waitKey(0)

- 輸出

[[[0 0 0]
[0 0 0]]

[[0 0 0]
[0 0 0]]]
(2, 2, 3)
小數點沒有了

### 例子3 藍色uint

import cv2
import numpy as np
img1 = np.zeros((200, 200, 3), np.uint8)
img1[:] = 255, 0, 0
img2 = np.zeros((200, 200, 3), np.uint8)
img2[:] = 65535, 0, 0
img3 = np.zeros((200, 200, 3), np.uint16)
img3[:] = 255, 0, 0
img4 = np.zeros((200, 200, 3), np.uint16)
img4[:] = 65535, 0, 0
print(img4)
print(img4.shape)
cv2.imshow("img1", img1)
cv2.imshow("img2", img2)
cv2.imshow("img3", img3)
cv2.imshow("img4", img4)
cv2.waitKey(0)


- 8位元與16位元

## 填滿的矩形

import cv2
import numpy as np
img1 = np.zeros((200, 200, 3), np.uint8)
img1[20:50,60:100] = 0, 0, 255
cv2.imshow("img1", img1)
cv2.waitKey(0)


- img1[] = 0, 0, 255順序表示 B G R

## 畫線

import cv2
import numpy as np
img1 = np.zeros((200, 200, 3), np.uint8)
img1[20:50,60:100] = 0, 0, 255
cv2.line (img1, (0, 0), (img1.shape[1], img1.shape[0]), (0, 255, 0), 3)
cv2.imshow("img1", img1)
cv2.waitKey(0)


- cv2.line (img1, (0, 0), (img1.shape[1], img1.shape[0]), (0, 255, 0), 3)
img1來源

(0, 0)線的開頭

(img1.shape[1], img1.shape[0])線的結尾

(0, 255, 0)顏色

3 粗細

## 畫邊的矩形(cv2.rectangle)

import cv2
import numpy as np
img1 = np.zeros((200, 200, 3), np.uint8)
img1[20:50,60:100] = 0, 0, 255
cv2.line (img1, (0, 0), (200, 200), (0, 255, 0), 3)
cv2.rectangle (img1, (80, 170), (20, 100),( 50, 10, 100),8)
cv2.imshow("img1", img1)
cv2.waitKey(0)


## 填滿(cv2.FILLED)

cv2.rectangle (img1, (150, 180), (100, 120),( 100, 200, 10),cv2.FILLED)

會覆蓋前面所輸入的線

加一段
## 圓形和文字

cv2.circle (img1, (99, 122), 90,(33, 66, 166),2)
cv2.putText (img1, "HAHAHA DODODO", (0, 270),cv2.FONT_HERSHEY_COMPLEX, 1,(23, 60, 100))


- cv2.circle 定義
def circle(img, center, radius, color, thickness=None, lineType=None, shift=None)

- cv2.putText定義
def putText(img, text, org, fontFace, fontScale, color, thickness=None, lineType=None, bottomLeftOrigin=None)

:::spoiler 一篇一個OpenCV函式(destroyWindow)
cv2.destroyWindow
原型： destroyWindow(winname)
作用：關閉一個由imshow產生的影象視窗
引數：winname，關閉的視窗名字

cv2.destroyAllWindows
原型：destroyAllWindows()
作用：關閉所有由imshow產生的視窗

https://www.itread01.com/content/1550310670.html
:::

:::spoiler 一篇一個numpy函式(partition)

np.partition(array, kth)
以 kth 為標準，排序後返回陣列。

import numpy as np
kth = 4
a = np.array([9, 1, 4, 0, 5, 9, 0, 2, 6, 0])
print("Hello kth = " + str(kth))

# Partition
print("Hello before partition a = " + str(a))
print("Hello after- partition a = " + str(np.partition(a, kth)))

- kth = 4 輸出

Hello kth = 4
Hello before partition a = [9 1 4 0 5 9 0 2 6 0]
Hello after partition a = [1 0 0 0 2 4 5 9 6 9]

- kth = 7 輸出

Hello kth = 7
Hello before partition a = [9 1 4 0 5 9 0 2 6 0]
Hello after- partition a = [0 0 4 0 1 2 5 6 9 9]

- kth = 1 輸出

Hello kth = 1
Hello before partition a = [9 1 4 0 5 9 0 2 6 0]
Hello after- partition a = [0 0 4 9 5 9 1 2 6 0]

- kth = 1,在陣列 a0、a1的值要跟1做比較，找到比1還小的值就要交換
這裡的a0是=9 ,9>=1 然後找到了a3=0，a0和a3交換了位置
這裡的a1是=1 ,1>=1 然後找到了a6=0，a0和a3交換了位置
程式執行結束

https://hackmd.io/@yillkid/rJp5h90s8/https%3A%2F%2Fhackmd.io%2F%40yillkid%2FHy5a_5A-F#array
:::
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