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  • opencv-python
  • ไธ€่ˆฌๆ€ง่ฏดๆ˜Ž
  • ๅ›พๅƒ่ฏปๅ†™ๆ“ไฝœ
  • RGB ไธŽ BGR ่ฝฌๆข๏ผˆcv2 ้ป˜่ฎคไฝฟ็”จ BGR ๆ ผๅผ๏ผ‰
  • ๅœจๅ›พๅƒไธŠ็ป˜ๅˆถ
  • ๅ›พๅƒๅ˜ๆข
  • opencv ๅค„็†่ง†้ข‘
  • ๅ›พๅƒไฟฎๅค
  • OpenCV C++ API
  • ๅฎ‰่ฃ…๏ผšwindows VS2017 + OpenCV C++
  • Tricks and Discussion and Have Fun
  • ๆ‰พไธๅˆฐๅ…ณไบŽ opencv-python ็š„ๅ‡†็กฎๆŽฅๅฃๆ–‡ๆกฃ

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  1. Note
  2. CV

OpenCV

opencv-python

ไธ€่ˆฌๆ€ง่ฏดๆ˜Ž

ๅฎ‰่ฃ…

่ฏฆ็ป†ๅฏไปฅๅ‚่€ƒ opencv-python ไป“ๅบ“็š„ README ๆ–‡ๆกฃ

pip install opencv-python  # ๆ— ้œ€ๅฆๅค–็ผ–่ฏ‘ๅฎ‰่ฃ…opencv

ๆณจๆ„๏ผŒๅญ˜ๅœจๅ››็งไฝฟ็”จ pip ็š„ๆ–นๅผ่ฟ›่กŒๅฎ‰่ฃ…๏ผŒไฝ†ๅช่ƒฝ้€‰ๆ‹ฉๅ…ถไธญ็š„ไธ€็ง๏ผŒ่‹ฅๅทฒ็ปๅฎ‰่ฃ…ไบ†ๅ…ถไธญ็š„ไธ€ไธช๏ผŒๆƒณ่ฆๅฎ‰่ฃ…ๅฆไธ€ไธช๏ผŒๅˆ™ๅฟ…้กปๅฐ†ไน‹ๅ‰็š„ไฝฟ็”จ pip uninstall ๅธ่ฝฝๆŽ‰ใ€‚

pip install opencv-python  # ๅชๅŒ…ๅซไธป่ฆ็š„ๆจกๅ—
pip install opencv-contrib-python  # ๅฎŒๆ•ดๅฎ‰่ฃ…๏ผšๅŒ…ๅซไธป่ฆๆจกๅ—ๅŠcontrib/extraๆจกๅ—
pip install opencv-python-headless # ๅŒ…ๅซไธป่ฆๆจกๅ—๏ผŒไฝ†ๅŽป้™คไบ†cv2.imshow่ฟ™็ง่พ“ๅ‡บ็š„ๅŠŸ่ƒฝ๏ผŒ้€‚็”จไบŽๆ— ๅ›พๅฝข็•Œ้ข็š„ๆœๅŠกๅ™จ๏ผŒไฝ“็งฏๆฏ”opencv-python่ฆๅฐ
pip install opencv-contrib-python-headless

ๅฏผๅ…ฅ

import cv2

ๆณจๆ„็‚น

  • cv2 ๅŒ…้‡Œๅ‡ฝๆ•ฐ็š„ๅ‚ๆ•ฐ size ไธ€่ˆฌไธบ (width, height)๏ผŒ่กจ็คบๅฎฝไธŽ้ซ˜ใ€‚

  • cv2 ไฝฟ็”จไฝฟ็”จ numpy ๆ•ฐ็ป„ๆฅ่กจ็คบๅ›พๅƒ๏ผŒๆ•ฐ็ป„็š„ๆ•ฐๆฎ็ฑปๅž‹ๅฟ…้กปไธบ uint8๏ผŒๅณ dtype=np.uint8ใ€‚ๅนถไธ”ๆ•ฐ็ป„็š„ๅฝข็Šถไธบ channel_last ็š„ๆ–นๅผ๏ผŒไพ‹ๅฆ‚๏ผš

    • RGB ๅ›พๅƒ็š„่กจ็คบๅฝขๅผๆ˜ฏๅฝข็Šถไธบ (H, W, 3) ็š„ๆ•ฐ็ป„๏ผŒๅ…ถไธญ้€š้“็š„ๅญ˜ๅ‚จ้กบๅบไธบ BGR๏ผŒ่ฎธๅคšๅ‡ฝๆ•ฐไพ‹ๅฆ‚ cv2.putText ๆ‹ฅๆœ‰ๅ‚ๆ•ฐ color ่กจ็คบ้ขœ่‰ฒ๏ผŒๅ…ถๅ–ๅ€ผๅฟ…้กปไธบไธ€ไธชๆ•ดๆ•ฐ็š„ไธ‰ๅ…ƒ็ป„๏ผŒไธ”ๅ–ๅ€ผไธบ [0, 255] ๅŒบ้—ดๅ†…็š„ๆ•ดๆ•ฐ๏ผŒๅŒๆ ท้ตๅพช BGR ็š„้กบๅบ๏ผŒไพ‹ๅฆ‚๏ผšcolor=(255, 0, 0) ่กจ็คบ่“่‰ฒใ€‚

    • ็ฐๅบฆๅ›พๅƒ็š„่กจ็คบๅฝขๅผๆ˜ฏๅฝข็Šถไธบ (H, W) ็š„ๆ•ฐ็ป„

  • cv2 ไธญ็š„ๅ‡ฝๆ•ฐๅฏน numpyๆ•ฐ็ป„่ฟ›่กŒๆ“ไฝœๆ—ถๅพ€ๅพ€้œ€่ฆ numpy ๆ•ฐ็ป„็š„ๅ†…้ƒจๅญ˜ๅ‚จๆ˜ฏ C ่ฟž็ปญ็š„๏ผŒnumpy ไธญๅฏนๆ•ฐ็ป„็š„ๆŸไบ›ๆ“ไฝœไผšไฝฟๅพ—ๆ•ฐ็ป„ๅ˜็š„ไธๆ˜ฏ C ่ฟž็ปญ็š„๏ผŒไพ‹ๅฆ‚๏ผš

    • np.transpose

    • ่ดŸ้—ด้š”็š„ๅˆ‡็‰‡ๆ“ไฝœ๏ผšarr = arr[::-1,:,:]

    ่ฟ™็งๆƒ…ๅ†ตไธ‹้œ€่ฆ้ฆ–ๅ…ˆไฝฟ็”จๅฆ‚ไธ‹ๆ–นๆณ•ๅฐ† numpy ๆ•ฐ็ป„่ฝฌๆข๏ผŒๅ†ๅˆฉ็”จ cv2 ็š„็›ธๅ…ณๅ‡ฝๆ•ฐๅฏน่ฝฌๆขๅŽ็š„ๆ•ฐ็ป„่ฟ›่กŒๆ“ไฝœ

    arr = np.ascontiguousarray(arr)

  • cv2 ็š„่ฎธๅคšๅ‡ฝๆ•ฐๆ˜ฏ inplace ็š„๏ผŒไพ‹ๅฆ‚ไธ€ไบ›็ป˜ๅˆถๅ›พๅƒ็š„ๅ‡ฝๆ•ฐใ€‚ไพ‹ๅฆ‚๏ผš

    import numpy as np
import cv2
image = np.zeros((224, 224, 3), dtype=np.uint8)
print(image.any())  # False
# ้€šๅธธ็š„ๅ†™ๆณ•ๆ˜ฏไธ้œ€่ฆๆŽฅๆ”ถ่ฟ”ๅ›žๅ€ผ็š„,ๆญคๅค„ๆ˜ฏไธบไบ†่ฏดๆ˜Ž้—ฎ้ข˜
x = cv2.putText(image, "mark", (100, 200), cv2.FONT_HERSHEY_COMPLEX, 5, (0, 0, 255))
print(x.any(), image.any(), x is image)  # True, True, True

    ๅฆ‚ๆžœไธๆƒณๅฏนๅŽŸๅ›พ่ฟ›่กŒไฟฎๆ”น๏ผŒ้œ€่ฆ้ฆ–ๅ…ˆ่ฐƒ็”จ numpy ๆ•ฐ็ป„็š„ copy ๆ–นๆณ•ๅ†่ฟ›่กŒๅค„็†๏ผŒไพ‹ๅฆ‚๏ผš

    image = np.zeros((224, 224, 3), dtype=np.uint8)
print(image.any())  # False
x = cv2.putText(image.copy(), "mark", (100, 200), cv2.FONT_HERSHEY_COMPLEX, 5, (0, 0, 255))
print(x.any(), image.any(), x is image)  # True, False, False

  • cv2 ้‡Œ่ฎธๅคšๅ‡ฝๆ•ฐ็š„ๅ‚ๆ•ฐ็š„ๅ–ๅ€ผไผšๆ˜ฏโ€œๆ ‡ๅฟ—ไฝโ€๏ผŒไพ‹ๅฆ‚๏ผšcv2.COLOR_BGR2RGB๏ผŒcv2.LINE_8๏ผŒๅ…ถๆฅๆบไบŽ opencv ็š„ C++ ๆบ็ ไธญๆ‰€ๅฎšไน‰็š„ๅฎ๏ผŒไธ€่ˆฌ็”จไบŽๆŽงๅˆถๅŒไธ€ๆŽฅๅฃไธ‹็š„ไธๅŒ็ฎ—ๆณ•๏ผŒ่ฟ™ไบ›ๆ ‡ๅฟ—ไฝๅฎž้™…ไธŠๆ˜ฏไธ€ไบ›ๆ•ดๆ•ฐ๏ผŒไพ‹ๅฆ‚๏ผšcv2.COLOR_BGR2RGB==4๏ผŒcv2.LINE_8==8ใ€‚้€šๅธธๆƒ…ๅ†ตไธ‹ๆŽจ่ไฝฟ็”จๅฎๅ่€Œไธ่ฆ็›ดๆŽฅไฝฟ็”จๅฎƒๆ‰€ไปฃ่กจ็š„ๆ•ดๆ•ฐใ€‚

ๅ›พๅƒ่ฏปๅ†™ๆ“ไฝœ

่ฏฆ็ป†ๅฏๅ‚่€ƒๅฎ˜ๆ–นๆ–‡ๆกฃ

imread ไธŽ imwrite

cv2.imread

cv2.imread(filename, flags=cv2.IMREAD_COLOR) -> bool
image = cv2.imread("x.jpg")

  • cv2.IMREAD_COLOR๏ผšๅพ—ๅˆฐ็š„ๅ›พๅƒไธบ BGR ๆ ผๅผ็š„ numpy ๆ•ฐ็ป„

  • cv2.IMREAD_UNCHANGED๏ผšๅŽŸๆ ท่งฃ็ ๏ผŒไพ‹ๅฆ‚๏ผš่‹ฅๅ›พๅƒๅŽŸๆœฌๅญ˜ๅ‚จไบ† RGBA ๆ ผๅผ็š„ๆ•ฐๆฎ๏ผŒๅˆ™่ฏปๅ‡บๆฅไนŸไผšๆ˜ฏๅ››้€š้“็š„ numpy ๆ•ฐ็ป„

  • cv2.IMREAD_GRAYSCALE๏ผšๅพ—ๅˆฐ็š„ๅ›พๅƒๆ˜ฏๅฝข็Šถไธบ (H, W) ็š„็ฐๅบฆๅ›พๅƒ

  • ...

ๅค‡ๆณจ๏ผš้œ€่ฆๆ ผๅค–ๆณจๆ„๏ผŒ่‹ฅ่ฏปๅ…ฅไธๆˆๅŠŸ๏ผŒๆฏ”ๅฆ‚ๆ–‡ไปถ่ทฏๅพ„ไธๅญ˜ๅœจ๏ผŒimage ๅฐ†ไผšๆ˜ฏ None๏ผŒไฝ†่ฏฅๆก่ฏปๅ…ฅ่ฏญๅฅๅนถไธไผšๆŠฅ้”™ๅผ•่ตท็จ‹ๅบไธญๆ–ญใ€‚

cv2.imwrite

cv2.imwrite(filename, img, params=()) -> bool
cv2.imwrite("x.jpg")

็ฌฌไธ‰ไธชๅ‚ๆ•ฐๅฏ้€‰๏ผŒๅซไน‰ๅฆ‚ไธ‹๏ผš

cv2.imwrite("x.jpg", img, (cv2.IMWRITE_JPEG_QUALITY๏ผŒ 95))  # jpgๆ ผๅผ้ป˜่ฎคๅ€ผ
cv2.imwrite("x.png", img, (cv2.IMWRITE_PNG_COMPRESSION, 3))  # pngๆ ผๅผ้ป˜่ฎคๅ€ผ

  • cv2.IMWRITE_JPEG_QUALITY=1๏ผšJPEG ๆ ผๅผ๏ผŒ0-100 ็š„ๆ•ดๆ•ฐ๏ผŒ่กจ็คบๅ›พๅƒ่ดจ้‡๏ผŒ้ป˜่ฎคไธบ 95ใ€‚

  • cv2.IMWRITE_PNG_COMPRESSION=16๏ผšPNG ๆ ผๅผ๏ผŒ0-9่กจ็คบๅŽ‹็ผฉ็บงๅˆซ๏ผŒ็บงๅˆซ่ถŠ้ซ˜ๅ›พๅƒ่ถŠๅฐ๏ผŒ้ป˜่ฎคๅ€ผไธบ 3ใ€‚

ๅค‡ๆณจ๏ผšJPEG ๆ ผๅผไธบๆœ‰ๆŸๅŽ‹็ผฉ๏ผ›่€Œ PNG ๆ ผๅผไธบๆ— ๆŸๅŽ‹็ผฉ๏ผŒPNG ็š„ๅŽ‹็ผฉ็บงๅˆซไผšๅฝฑๅ“็ผ–็ ่งฃ็ ๆ—ถ้—ดใ€‚

ๅค‡ๆณจ๏ผšimread ไธŽ imwrite ็š„่ฟ”ๅ›žๅ€ผ่‹ฅไธบ True๏ผŒๅˆ™่กจ็คบ่ฏปๅ…ฅๆˆ–ๅ†™ๅ…ฅๆˆๅŠŸ๏ผŒๅฆๅˆ™่กจ็คบๅคฑ่ดฅใ€‚

imencode ไธŽ imdecode

imread ไธŽ imwrite ๆ˜ฏ้ซ˜็บงๆŽฅๅฃ๏ผŒๅฝ“่ทฏๅพ„ไธญๅญ˜ๅœจไธญๆ–‡ๅญ—็ฌฆๆ—ถ๏ผŒimread ไธŽ imwrite ไผšๆ— ๆณ•่ฏปๅ†™ๆ–‡ไปถ๏ผŒ่ฟ™็งๆ—ถๅ€™ๅฏไปฅ็ป“ๅˆ numpy ่ฟ›่กŒๅค„็†๏ผš

  • ๅˆฉ็”จไฝŽ็บงๆŽฅๅฃ imencode ไธŽ imdecode ๅฏนๆ•ฐๆฎ่ฟ›่กŒ็ผ–็ ไธŽ่งฃ็ 

  • ๆ–‡ไปถ IO ๆ“ไฝœไฝฟ็”จ numpy ็š„็›ธๅ…ณๆ–นๆณ•ไพ‹ๅฆ‚ fromfile๏ผŒtofile ็ญ‰ๆ–นๆณ•่ฟ›่กŒ

้ฆ–ๅ…ˆไป‹็ป imencode ไธŽ imdecode ๆ–นๆณ•

cv2.imencode

cv2.imencode(ext, img, params=()) -> (bool, np.array)
# ext่กจ็คบๆ‰ฉๅฑ•ๅ,็”จไบŽๅ†ณๅฎšๅŽ‹็ผฉๆ–นๅผ, imgไธบ(H,W[,C])ๆ•ฐ็ป„,paramsไธบๅŽ‹็ผฉๅ‚ๆ•ฐ
# flag=True่กจ็คบ็ผ–็ ๆˆๅŠŸ, encoded_imgๆ˜ฏไธ€ไธชๅฝข็Šถไธบ(K, 1)็š„uint8ๆ•ฐ็ป„
flag, encoded_img = cv2.imencode(".jpg", img, (cv2.IMWRITE_JPEG_QUALITY๏ผŒ 95))

cv2.imdecode

cv2.imdecode(buf, flags) -> np.array
# arrๅฏไปฅๆ˜ฏไธ€ไธช(K,)็š„uint8ๆ•ฐ็ป„, flags็š„ๅ–ๅ€ผไธŽimreadไธ€่‡ด
cv2.imdecode(arr, cv2.IMREAD_COLOR)

ๆณจ๏ผšๆญคๅค„ไผผไนŽๆ— ้œ€ๆŒ‡ๅฎšๆŒ‰ไป€ไนˆๆ–นๅผ่งฃ็ ๏ผŒๆœ‰ไบ›ๅฏ็–‘ใ€‚

x = np.zeros((224, 224, 3))
y = cv2.imdecode(cv2.imencode(".png", x)[1], cv2.IMREAD_UNCHANGED)
(x==y).all()  # True

ๆŽฅไธ‹ๆฅไป‹็ป numpy ็š„็›ธๅ…ณๆ–นๆณ•๏ผŒๆณจๆ„่ฟ™ไบ›ๆ–นๆณ•ๆ˜ฏไธŽ cv2 ๆ— ๅ…ณ็š„ไธ€ๅฅ— numpy ๅญ˜ๅ‚จๆ–‡ไปถ็š„ๅšๆณ•ใ€‚

np.ndarray.tofileใ€np.ndarray.tobytes

np.ndarray.tofile ็”จไบŽๅฐ†ๆ•ฐ็ป„ๅญ˜ๅ…ฅๆ–‡ไปถ

arr.tofile(path, ...) -> None
arr.tofile("x.png")

ๆ›ด็ป†่‡ด็š„ๅ†™ๅ…ฅๆ–นๅผๆ˜ฏ๏ผŒๅ…ˆๅฐ†ๆ•ฐ็ป„็”จ np.tobytes ่ฝฌๆขไธบๅญ—่Š‚๏ผŒๅ†ๅฐ†็š„ๅพ—ๅˆฐ็š„ๅญ—่Š‚ไปฅไบŒ่ฟ›ๅˆถๅฝขๅผๅ†™ๅ…ฅๆ–‡ไปถ

b = cv2.imencode(".png", image)[1].tobytes()
with open("x.png", "wb") as fw:
    fw.write(b)
(cv2.imread("x.png") == image).all()  # True

np.fromfile ็”จไบŽ่ฏปๅ–็”จ np.ndarray.tofile ๅญ˜ๅ…ฅ็š„ๆ–‡ไปถ

np.fromfile(path, dtype=np.uint8, ...) -> np.array
arr = np.fromfile("x.jpg", dtype=np.uint8)

ๆ›ด็ป†่‡ด็š„่ฏปๅ–ๆ–นๅผๆ˜ฏ๏ผŒๅ…ˆๅฐ†่ฆ่ฏปๅ–็š„ๆ–‡ไปถไปฅไบŒ่ฟ›ๅˆถๅฝขๅผ่ฏปๅ–๏ผŒๅ†ๅฐ†ๅพ—ๅˆฐ็š„ๅญ—่Š‚็”จ np.frombuffer ๅพ—ๅˆฐ

with open("x.png", "rb") as fr:
	b = fr.read()
image = cv2.imdecode(np.frombuffer(b, np.uint8), cv2.IMREAD_UNCHANGED)

ๆ€ป็ป“๏ผˆๅคช้•ฟไธ็œ‹็š„็›ดๆŽฅ็œ‹่ฟ™้‡Œ๏ผ‰

# ๅ†™ๆ–‡ไปถ, ไธค็ง้ƒฝๅฏไปฅ
cv2.imencode(".jpg", image)[1].tofile(path)  # image: (H, W, 3) np.ndarray, uint8, BGR format

b = cv2.imencode(".png", image)[1].tobytes()
with open("x.png", "wb") as fw:
    fw.write(b)
# ่ฏปๆ–‡ไปถ, ไธค็ง้ƒฝๅฏไปฅ
image = cv2.imdecode(np.fromfile(path, dtype=np.uint8), cv2.IMREAD_COLOR)  # image: (H, W, 3) np.ndarray, uint8, BGR format

with open("a.jpg", "rb") as fr:
    b = fr.read()
image = cv2.imdecode(np.frombuffer(b, np.uint8), cv2.IMREAD_UNCHANGED)

RGB ไธŽ BGR ่ฝฌๆข๏ผˆcv2 ้ป˜่ฎคไฝฟ็”จ BGR ๆ ผๅผ๏ผ‰

# ๅฐ†srcBGR: uint8ๆ•ฐ็ป„(H, W, 3)่ฝฌๆขไธบdestRGB: uint8ๆ•ฐ็ป„(H, W, 3)
destRGB = cv2.cvtColor(srcBGR, cv2.COLOR_BGR2RGB)

ๅค‡ๆณจ๏ผšๅฏไปฅ่ฐƒๆ•ด cv2.cvtColor ๅ‡ฝๆ•ฐ็š„็ฌฌไบŒไธชๅ‚ๆ•ฐ็š„ๅ–ๅ€ผ่ฟ›่กŒ่ฎธๅคšๅ…ถไป–็š„่ฝฌๆข๏ผŒไพ‹ๅฆ‚๏ผš

  • cv2.COLOR_BGR2GRAY๏ผš่กจ็คบๅฐ† BGR ๅ›พ็‰‡่ฝฌๆขไธบ็ฐๅบฆๅ›พ็‰‡

ๅœจๅ›พๅƒไธŠ็ป˜ๅˆถ

่ฏฆ็ป†ๅฏๅ‚่€ƒๅฎ˜ๆ–นๆ–‡ๆกฃ

็”ป็‚น๏ผˆๅฎž้™…ไธŠๆ˜ฏๅœจ็”ปๅœˆ๏ผ‰

cv.circle(img, center, radius, color, thickness=1, lineType=cv2.LINE_8, shift=0)
# centerไธบๅ…ƒ็ป„(x, y), radius่กจ็คบๅŠๅพ„, colorไธบไธ‰ๅ…ƒ็ป„(B, G, R), thickness่กจ็คบ็บฟ็š„็ฒ—็ป†
cv2.circle(img, (100, 20), 2, (0, 0, 255), thickness=2)

ๅค‡ๆณจ๏ผš

  • lineType๏ผš

ๆทปๅŠ ๆ–‡ๅญ—๏ผˆ้ž่‹ฑๆ–‡ไผšไนฑ็ ๏ผ‰

ๅ…ณไบŽbottomLeftOrigin็š„ๆœ‰้”™๏ผŒๅพ…่กฅๅ……

cv2.putText(image, text, org, font, fontScale, color, thickness=1, lineType=cv2.LINE_8, bottomLeftOrigin=False)
# orgๆ˜ฏๅๆ ‡,fontๆ˜ฏๅญ—ไฝ“,fontScaleๆ˜ฏๅญ—ไฝ“
# ๅฝ“bottomLeftOriginไธบTrueๆ—ถ,่กจ็คบorgๆ˜ฏๆ–‡ๅญ—็š„ๅทฆไธ‹่ง’ๅๆ ‡,ๅ–ๅ€ผไธบFalseๆ—ถ๏ผˆ้ป˜่ฎคๅ€ผ๏ผ‰่กจ็คบorgไธบๆ–‡ๅญ—็š„ๅทฆไธŠ่ง’ๅๆ ‡,ๅ–ๅ€ผไธบTrueๆ—ถ่กจ็คบorgไธบๆ–‡ๅญ—็š„ๅทฆไธ‹่ง’ๅๆ ‡
cv2.putText(image, "mark", (100, 200), cv2.FONT_HERSHEY_COMPLEX, 5, (0, 0, 255), thickness=2, bottomLeftOrigin=True)

่Žทๅ–ๅญ—ไฝ“ๅคงๅฐ

ๆทปๅŠ ็บฟใ€็Ÿฉๅฝขใ€ๅคš่พนๅฝข

็”ป็บฟๆฎต

cv2.line(img, pt1, pt2, color[, thickness, lineType[, shift]])
# pt1,pt2ๅˆ†ๅˆซไธบ่ตท็‚นๅ’Œ็ปˆ็‚น
cv2.line(img, (10, 10), (200, 10), (0, 0, 255))

็”ป็Ÿฉๅฝข

cv2.rectangle(img, pt1, pt2, color[, thickness[, lineType[, shift]]]) -> img
# pt1, pt2ไธบๅทฆไธŠไธŽๅณไธ‹่ง’็š„ๅๆ ‡
cv2.rectangle(image, (10, 10), (20, 30), (0, 0, 255))

็”ปๅคš่พนๅฝข

ๆ–นๆณ•ไธ€๏ผšไฝฟ็”จ cv2.polylines

# ๆญคๅ‡ฝๆ•ฐ็”จไบŽ็”ปๅคšไธช็›ธๅŒbๅคš่พนๅฝข
cv2.polylines(img, pts, isClosed, color[, thickness[, lineType, [shift]]])
# pts ็š„ไผ ๅ‚ๆ–นๅผๅพˆ่ฏกๅผ‚:

# ็”ปไธ€ไธชๅ››่พนๅฝข
# (1)ptsๅฏไปฅไฝฟ็”จไธ€ไธช้•ฟๅบฆไธบ1็š„ๅˆ—่กจ, ๅˆ—่กจๅ†…ไธบไธ€ไธช(4, 2)ๅฝข็Šถ็š„ๆ•ฐ็ป„: [(4, 2)]
# (2)ptsไนŸๅฏไปฅไฝฟ็”จไธ€ไธชๅฝข็Šถไธบ(1, 4, 2)็š„ๆ•ฐ็ป„: (1, 4, 2)
pts = np.array([[10, 10], [30, 30], [20, 30], [10, 20]])
cv2.polylines(img, [pts], True, (0, 0, 255))

# ็”ปKไธชๅคšๅ››่พนๅฝข
# (1)ptsๅฏไปฅไฝฟ็”จไธ€ไธช้•ฟๅบฆไธบK็š„ๅˆ—่กจ, ๅˆ—่กจๅ†…ไธบไธ€ไธช(4, 2)ๅฝข็Šถ็š„ๆ•ฐ็ป„: [(4, 2),...,(4,2)]
# (2)ptsไนŸๅฏไปฅไฝฟ็”จไธ€ไธชๅฝข็Šถไธบ(K, 4, 2)็š„ๆ•ฐ็ป„: (K, 4, 2)
pts = np.array([[[10, 10], [30, 30], [20, 30], [10, 20]],
                [[110, 110], [130, 130], [120, 130], [110, 120]]])
cv2.polylines(img, pts, True, (0, 0, 255))

# ่ฏกๅผ‚็š„ๆ˜ฏ [(4, 1, 2)], [(1, 4, 2)] ่ฟ™็งไผ ๆณ•ไนŸๆ˜ฏๅฏน็š„

ๆ–นๆณ•ไบŒ๏ผšไฝฟ็”จ cv2.drawContours

cv2.drawContours(image, contours, contourIdx, color[, thickness[, lineType[, hierarchy[, maxLevel[, offset]]]]]) -> image
# contoursไธบไธ€ไธชไบŒ็ปดๆ•ฐ็ป„็š„ๅˆ—่กจ, ไบŒ็ปดๆ•ฐ็ป„็š„ๅฝข็Šถไธบ(K, 2)
# contoursIdxไธบไธ€ไธชๆ•ดๆ•ฐ, ่กจ็คบ่ฆ็”ป้‚ฃไธช, ่‹ฅๅ–ๅ€ผไธบ-1, ๅˆ™่กจ็คบๅ…จ้ƒจ็”ปๅ‡บ
contours = np.array([[20, 20], [40, 20], [40, 40], [30, 30], [20, 40]])
cv2.drawContours(image, [contours], 0, (0, 0, 255))

ๅ›พๅƒๅ˜ๆข

import sklearn.transform as trans
tform = trans.SimilarityTransform()
src = np.array([[100, 100], [200, 50], [200, 200], [100, 150]])
dst = np.array([[60, 70], [80, 70], [80, 100], [60, 100]])
tform.estimate(src, dst)
M = tform.params  # 3*3ๆ•ฐ็ป„, ๆœ€ๅŽไธ€่กŒไธบ[0, 0, 1]

src3d = np.ones(3, src.shape[0])
src3d[:-1, :] = src.T
# M @ src3d ~= dst
# M = 
# [[a0, -b0, a1],
#  [b0,  a0,  b1],
#  [0,   0,   1]]

ๅ˜ๆขๅ…ฌๅผไธบ๏ผˆtform.estimate ๅฎž้™…ไธŠๅฐฑๆ˜ฏๅœจไผฐ่ฎก M๏ผ‰๏ผš

ๅณ๏ผš

cv2.minAreaRect

# bbox: (k, 2) np.array
center_point, w_h, angle = cv2.minAreaRect(bbox)
# angle่กจ็คบๆ—‹ๆญฃๅŽ็š„็Ÿฉๅฝข้œ€่ฆ็ป•center_point้€†ๆ—ถ้’ˆๆ—‹่ฝฌๅคšๅฐ‘ๅบฆๆ‰่ƒฝๅ˜ๆขๅˆฐbbox,็Ÿฉๅฝข็š„ๅฎฝ้ซ˜ๅˆ†ๅˆซไธบw_h
# w_h: ๆœ€ๅฐ็Ÿฉๅฝข็š„ๅฎฝๅ’Œ้ซ˜
# center_point๏ผšbbox็š„ไธญๅฟƒ็‚น
# ๅค‡ๆณจ๏ผšbbox้‡Œ็š„็‚น็š„้กบๅบๅฏไปฅๆ˜ฏไปปๆ„็š„๏ผŒๅพ—ๅˆฐ็š„็ป“ๆžœๆ˜ฏไธ€่‡ด็š„

cv2.getRotationMatrix2D

ๆญคๅ‡ฝๆ•ฐ็”จไบŽ่Žทๅ–็ป•ๆŸไธ€ไธญๅฟƒ็‚นๆ—‹่ฝฌๅŽ็š„ๅ˜ๆข็Ÿฉ้˜ต

ๆ•…ๅ˜ๆข็Ÿฉ้˜ตไธบ๏ผš

M = cv2.getRotationMatrix2D(center, angle, scale)
# Mๆ˜ฏๅฝข็Šถไธบ(2, 3)็š„np.arrayๆ•ฐ็ป„, centerๅณไธบไธŠไพ‹็š„(x0,y0), angleๅณไธบtheta, scaleๅณไธบalpha

cv2.warpAffine

dst = cv.warpAffine(src, M, dsize[, dst[, flags[, borderMode[, borderValue]]]])
# Mๆ˜ฏไธ€ไธช2*3็š„ๆ•ฐ็ป„, srcไธบๅ›พๅƒ, dsizeไธบ็›ฎๆ ‡ๅ›พๅƒdst็š„ๅคงๅฐ(w,h), flags่กจ็คบๆ’ๅ€ผๆ–นๅผ

้€†ๅ˜ๆขๆ–นๅผๅฏไปฅๆŽจ็ฎ—ไธบ

cv2.getPespectiveTransform๏ผˆๅพ…่กฅๅ……๏ผ‰

ไธŽfindHomography, warpPerspective, perspectiveTransform็›ธๅ…ณ

ๆฑ‚่งฃๅฆ‚ไธ‹ๆ–น็จ‹

M = cv.getPerspectiveTransform(src, dst[, solveMethod])
# src, dstๅ‡ไธบ(4, 2)ๆ•ฐ็ป„, ๆฑ‚่งฃ็š„Mไธบ3*3ๆ•ฐ็ป„

opencv ๅค„็†่ง†้ข‘

import cv2
cap = cv2.VideoCapture("xx.mp4")
total_frames: float = cap.get(cv2.CAP_PROP_FRAME_COUNT)  # ๆ€ปๅธงๆ•ฐ
fps: float = cap.get(cv2.CAP_PROP_FPS)  # ๆฏ็ง’็š„ๅธงๆ•ฐ
cap.set(cv2.CAP_PROP_POS_FRAMES, 3)  # ๅ–็ฌฌไธ‰ๅธง
succeed: bool, frame: np.ndarray = cap.read()  # ๅ–็ฌฌไธ‰ๅธง, frameๅณไธบ(H, W, 3) uint8, BGR cv2ๆ ผๅผ็š„ๅ›พ็‰‡

ๅ›พๅƒไฟฎๅค

cv2.inpaint

OpenCV C++ API

ๅฎ‰่ฃ…๏ผšwindows VS2017 + OpenCV C++

https://sevenold.github.io/2019/01/opencv-setup/

Tricks and Discussion and Have Fun

ๆ‰พไธๅˆฐๅ…ณไบŽ opencv-python ็š„ๅ‡†็กฎๆŽฅๅฃๆ–‡ๆกฃ

PreviousCVNextmmlab

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๏ผˆๅฏ่ทณๅˆฐๆœ€ๅŽ็›ดๆŽฅ็œ‹ๆ€ป็ป“๏ผ‰

dstx=a0โˆ—srcxโˆ’b0โˆ—srcy+a1=sโˆ—[srcxโˆ—cos(ฮธ)โˆ’srcyโˆ—sin(ฮธ)]+a1dsty=b0โˆ—srcx+a0โˆ—srcy+b1=sโˆ—[srcxโˆ—sin(ฮธ)+srcyโˆ—cos(ฮธ)]+b1\begin{align} dst_x &= a_0*src_x-b_0*src_y+a_1\\ &=s*[src_x*cos(\theta)-src_y*sin(\theta)]+a_1\\ dst_y &= b_0*src_x+a_0*src_y+b_1\\ &=s*[src_x*sin(\theta)+src_y*cos(\theta)]+b_1 \end{align}dstxโ€‹dstyโ€‹โ€‹=a0โ€‹โˆ—srcxโ€‹โˆ’b0โ€‹โˆ—srcyโ€‹+a1โ€‹=sโˆ—[srcxโ€‹โˆ—cos(ฮธ)โˆ’srcyโ€‹โˆ—sin(ฮธ)]+a1โ€‹=b0โ€‹โˆ—srcxโ€‹+a0โ€‹โˆ—srcyโ€‹+b1โ€‹=sโˆ—[srcxโ€‹โˆ—sin(ฮธ)+srcyโ€‹โˆ—cos(ฮธ)]+b1โ€‹โ€‹โ€‹
[dstxdsty0]=[a0โˆ’b0a1b0a0b1001][srcxsrcy0]\begin{bmatrix} dst_x\\dst_y\\0 \end{bmatrix} = \begin{bmatrix} a_0&-b_0&a_1\\ b_0&a_0&b_1\\ 0&0&1 \end{bmatrix} \begin{bmatrix} src_x\\src_y\\0 \end{bmatrix}โ€‹dstxโ€‹dstyโ€‹0โ€‹โ€‹=โ€‹a0โ€‹b0โ€‹0โ€‹โˆ’b0โ€‹a0โ€‹0โ€‹a1โ€‹b1โ€‹1โ€‹โ€‹โ€‹srcxโ€‹srcyโ€‹0โ€‹โ€‹
[dstx1dsty1]=โ‹ฏ=ฮฑ[cosฮธsinฮธโˆ’sinฮธcosฮธ][x1โˆ’x0y1โˆ’y0]+[x0y0]\begin{bmatrix} dstx_1\\dsty_1 \end{bmatrix}=\cdots=\alpha \begin{bmatrix} cos\theta&sin\theta\\ -sin\theta&cos\theta \end{bmatrix} \begin{bmatrix} x_1-x_0\\ y_1-y_0 \end{bmatrix}+ \begin{bmatrix} x_0\\ y_0 \end{bmatrix}[dstx1โ€‹dsty1โ€‹โ€‹]=โ‹ฏ=ฮฑ[cosฮธโˆ’sinฮธโ€‹sinฮธcosฮธโ€‹][x1โ€‹โˆ’x0โ€‹y1โ€‹โˆ’y0โ€‹โ€‹]+[x0โ€‹y0โ€‹โ€‹]
M=[ฮฑM0,(Iโˆ’ฮฑM0)[x0y0]]โˆˆR2ร—3M=[\alpha M_0,(I-\alpha M_0)\begin{bmatrix}x_0\\y_0\end{bmatrix}]\in\mathbb{R}^{2\times3}M=[ฮฑM0โ€‹,(Iโˆ’ฮฑM0โ€‹)[x0โ€‹y0โ€‹โ€‹]]โˆˆR2ร—3
[dstx,dsty]T=M[:,:โˆ’1][x,y]T+M[:,:โˆ’1][dst_x,dst_y]^T=M[:,:-1][x,y]^T+M[:,:-1][dstxโ€‹,dstyโ€‹]T=M[:,:โˆ’1][x,y]T+M[:,:โˆ’1]
(x,y)=M[:,:โˆ’1]โˆ’1(dstx,dsty)โˆ’M[:,:โˆ’1]โˆ’1M[:,โˆ’1](x,y)=M[:,:-1]^{-1}(dst_x,dst_y)-M[:,:-1]^{-1}M[:,-1](x,y)=M[:,:โˆ’1]โˆ’1(dstxโ€‹,dstyโ€‹)โˆ’M[:,:โˆ’1]โˆ’1M[:,โˆ’1]
[tixiโ€ฒtiyiโ€ฒti]=M[xiyi1]i=0,1,2,3\begin{bmatrix} t_ix_i'\\t_iy_i'\\t_i \end{bmatrix}=M \begin{bmatrix} x_i\\y_i\\1 \end{bmatrix} \quad i=0,1,2,3โ€‹tiโ€‹xiโ€ฒโ€‹tiโ€‹yiโ€ฒโ€‹tiโ€‹โ€‹โ€‹=Mโ€‹xiโ€‹yiโ€‹1โ€‹โ€‹i=0,1,2,3

ไผผไนŽ็š„็กฎๆ˜ฏๆฒกๆœ‰๏ผŒ็›ฎๅ‰่ƒฝๆ‰พๅˆฐ็š„ๅชๆ˜ฏๅฎ˜ๆ–น็š„python-tutorial๏ผŒไปฅๅŠ C++ ๆŽฅๅฃๆ–‡ๆกฃ้‡Œ้™„ไธŠ็š„ๅ…ณไบŽpythonๆŽฅๅฃ็š„็ฎ€่ฆ่ฏดๆ˜Žใ€‚

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