OpenCV Color spaces

Ref: https://docs.opencv.org/master/

BGR, RGB, YUV, HSV 등은 8 bits 3 채널로 픽셀마다 24 bits 값을 갖고, Grayscale은 8 bits 1 채널로 픽셀마다 8 bits 값을 갖습니다.

알파채널이 추가된 RGBA 등은 8 bits 4 채널로 픽셀마다 32 bits 값을 갖습니다.

이미지 배열은 (가로, 세로, 채널) 3 차원 배열로 이루어져있고, 1 채널 이미지의 경우 (가로, 세로) 2 차원 배열로 표현할 수 있습니다.

BGR 3 채널이 기본으로 사용됩니다.

예를 들어 400x400 빨간색 빈 이미지를 생성하고 싶을 때, 아래와 같은 코드를 이용할 수 있습니다.

import cv2 as cv
import numpy as np

image = np.zeros((400,400,3), dtype=np.uint8)
image[:,:,2] = 255
cv.imshow('red', image)
cv.waitKey()

BGR

import cv2 as cv
import numpy as np

bgr_image = np.array([[[255,  0,  0],[  0,255,  0],[  0,  0,255]],
                      [[255,255,  0],[255,  0,255],[  0,255,255]]],
                     dtype=np.uint8)
cv.imshow('bgr', bgr_image)
cv.waitKey()

Grayscale

import cv2 as cv
import numpy as np

gray_image = np.array([[  0,127,255],
                       [255,127,  0]],
                      dtype=np.uint8)
cv.imshow('gray', gray_image)
cv.waitKey()

RGB, HSV, HSL 색 공간

• Hue(색상) : 8 bits로 볼때 R=0(0$^{\circ}$), G=60(120$^{\circ}$), B=120(240$^{\circ}$)
• Saturation(채도)
• Value(명도)
• Lightness(밝기)

색 공간(color space) 변환

dst = cv.cvtColor(src, code, dst=None, dstCn=0)

• @brief src 색 공간을 code에 따라 변환한 후, dst로 반환
• @param src: np.ndarray
• @param dstCn: 0 으로 설정할 경우 src와 code에 따라 자동 설정
• @param code
  • cv.COLOR_BGR2BGRA = 0
  • cv.COLOR_RGB2RGBA = COLOR_BGR2BGRA
  • cv.COLOR_BGRA2BGR = 1
  • cv.COLOR_RGBA2RGB = COLOR_BGRA2BGR
  • cv.COLOR_BGR2RGBA = 2
  • cv.COLOR_RGB2BGRA = COLOR_BGR2RGBA
  • cv.COLOR_RGBA2BGR = 3
  • cv.COLOR_BGRA2RGB = COLOR_RGBA2BGR
  • cv.COLOR_BGR2RGB = 4
  • cv.COLOR_RGB2BGR = COLOR_BGR2RGB
  • cv.COLOR_BGRA2RGBA = 5
  • cv.COLOR_RGBA2BGRA = COLOR_BGRA2RGBA
  • cv.COLOR_BGR2GRAY = 6
  • cv.COLOR_RGB2GRAY = 7
  • cv.COLOR_GRAY2BGR = 8
  • cv.COLOR_GRAY2RGB = COLOR_GRAY2BGR
  • cv.COLOR_GRAY2BGRA = 9
  • cv.COLOR_GRAY2RGBA = COLOR_GRAY2BGRA
  • cv.COLOR_BGRA2GRAY = 10
  • cv.COLOR_RGBA2GRAY = 11
  • cv.COLOR_BGR2BGR565 = 12
  • cv.COLOR_RGB2BGR565 = 13
  • cv.COLOR_BGR5652BGR = 14
  • cv.COLOR_BGR5652RGB = 15
  • cv.COLOR_BGRA2BGR565 = 16
  • cv.COLOR_RGBA2BGR565 = 17
  • cv.COLOR_BGR5652BGRA = 18
  • cv.COLOR_BGR5652RGBA = 19
  • cv.COLOR_GRAY2BGR565 = 20
  • cv.COLOR_BGR5652GRAY = 21
  • cv.COLOR_BGR2BGR555 = 22
  • cv.COLOR_RGB2BGR555 = 23
  • cv.COLOR_BGR5552BGR = 24
  • cv.COLOR_BGR5552RGB = 25
  • cv.COLOR_BGRA2BGR555 = 26
  • cv.COLOR_RGBA2BGR555 = 27
  • cv.COLOR_BGR5552BGRA = 28
  • cv.COLOR_BGR5552RGBA = 29
  • cv.COLOR_GRAY2BGR555 = 30
  • cv.COLOR_BGR5552GRAY = 31
  • cv.COLOR_BGR2XYZ = 32
  • cv.COLOR_RGB2XYZ = 33
  • cv.COLOR_XYZ2BGR = 34
  • cv.COLOR_XYZ2RGB = 35
  • cv.COLOR_BGR2YCrCb = 36
  • cv.COLOR_RGB2YCrCb = 37
  • cv.COLOR_YCrCb2BGR = 38
  • cv.COLOR_YCrCb2RGB = 39
  • cv.COLOR_BGR2HSV = 40
  • cv.COLOR_RGB2HSV = 41
  • cv.COLOR_BGR2Lab = 44
  • cv.COLOR_RGB2Lab = 45
  • cv.COLOR_BGR2Luv = 50
  • cv.COLOR_RGB2Luv = 51
  • cv.COLOR_BGR2HLS = 52
  • cv.COLOR_RGB2HLS = 53
  • cv.COLOR_HSV2BGR = 54
  • cv.COLOR_HSV2RGB = 55
  • cv.COLOR_Lab2BGR = 56
  • cv.COLOR_Lab2RGB = 57
  • cv.COLOR_Luv2BGR = 58
  • cv.COLOR_Luv2RGB = 59
  • cv.COLOR_HLS2BGR = 60
  • cv.COLOR_HLS2RGB = 61
  • cv.COLOR_BGR2HSV_FULL = 66
  • cv.COLOR_RGB2HSV_FULL = 67
  • cv.COLOR_BGR2HLS_FULL = 68
  • cv.COLOR_RGB2HLS_FULL = 69
  • cv.COLOR_HSV2BGR_FULL = 70
  • cv.COLOR_HSV2RGB_FULL = 71
  • cv.COLOR_HLS2BGR_FULL = 72
  • cv.COLOR_HLS2RGB_FULL = 73
  • cv.COLOR_LBGR2Lab = 74
  • cv.COLOR_LRGB2Lab = 75
  • cv.COLOR_LBGR2Luv = 76
  • cv.COLOR_LRGB2Luv = 77
  • cv.COLOR_Lab2LBGR = 78
  • cv.COLOR_Lab2LRGB = 79
  • cv.COLOR_Luv2LBGR = 80
  • cv.COLOR_Luv2LRGB = 81
  • cv.COLOR_BGR2YUV = 82
  • cv.COLOR_RGB2YUV = 83
  • cv.COLOR_YUV2BGR = 84
  • cv.COLOR_YUV2RGB = 85
  • cv.COLOR_YUV2RGB_NV12 = 90
  • cv.COLOR_YUV2BGR_NV12 = 91
  • cv.COLOR_YUV2RGB_NV21 = 92
  • cv.COLOR_YUV2BGR_NV21 = 93
  • cv.COLOR_YUV420sp2RGB = COLOR_YUV2RGB_NV21
  • cv.COLOR_YUV420sp2BGR = COLOR_YUV2BGR_NV21
  • cv.COLOR_YUV2RGBA_NV12 = 94
  • cv.COLOR_YUV2BGRA_NV12 = 95
  • cv.COLOR_YUV2RGBA_NV21 = 96
  • cv.COLOR_YUV2BGRA_NV21 = 97
  • cv.COLOR_YUV420sp2RGBA = COLOR_YUV2RGBA_NV21
  • cv.COLOR_YUV420sp2BGRA = COLOR_YUV2BGRA_NV21
  • cv.COLOR_YUV2RGB_YV12 = 98
  • cv.COLOR_YUV2BGR_YV12 = 99
  • cv.COLOR_YUV2RGB_IYUV = 100
  • cv.COLOR_YUV2BGR_IYUV = 101
  • cv.COLOR_YUV2RGB_I420 = COLOR_YUV2RGB_IYUV
  • cv.COLOR_YUV2BGR_I420 = COLOR_YUV2BGR_IYUV
  • cv.COLOR_YUV420p2RGB = COLOR_YUV2RGB_YV12
  • cv.COLOR_YUV420p2BGR = COLOR_YUV2BGR_YV12
  • cv.COLOR_YUV2RGBA_YV12 = 102
  • cv.COLOR_YUV2BGRA_YV12 = 103
  • cv.COLOR_YUV2RGBA_IYUV = 104
  • cv.COLOR_YUV2BGRA_IYUV = 105
  • cv.COLOR_YUV2RGBA_I420 = COLOR_YUV2RGBA_IYUV
  • cv.COLOR_YUV2BGRA_I420 = COLOR_YUV2BGRA_IYUV
  • cv.COLOR_YUV420p2RGBA = COLOR_YUV2RGBA_YV12
  • cv.COLOR_YUV420p2BGRA = COLOR_YUV2BGRA_YV12
  • cv.COLOR_YUV2GRAY_420 = 106
  • cv.COLOR_YUV2GRAY_NV21 = COLOR_YUV2GRAY_420
  • cv.COLOR_YUV2GRAY_NV12 = COLOR_YUV2GRAY_420
  • cv.COLOR_YUV2GRAY_YV12 = COLOR_YUV2GRAY_420
  • cv.COLOR_YUV2GRAY_IYUV = COLOR_YUV2GRAY_420
  • cv.COLOR_YUV2GRAY_I420 = COLOR_YUV2GRAY_420
  • cv.COLOR_YUV420sp2GRAY = COLOR_YUV2GRAY_420
  • cv.COLOR_YUV420p2GRAY = COLOR_YUV2GRAY_420
  • cv.COLOR_YUV2RGB_UYVY = 107
  • cv.COLOR_YUV2BGR_UYVY = 108
  • cv.COLOR_YUV2RGB_Y422 = COLOR_YUV2RGB_UYVY
  • cv.COLOR_YUV2BGR_Y422 = COLOR_YUV2BGR_UYVY
  • cv.COLOR_YUV2RGB_UYNV = COLOR_YUV2RGB_UYVY
  • cv.COLOR_YUV2BGR_UYNV = COLOR_YUV2BGR_UYVY
  • cv.COLOR_YUV2RGBA_UYVY = 111
  • cv.COLOR_YUV2BGRA_UYVY = 112
  • cv.COLOR_YUV2RGBA_Y422 = COLOR_YUV2RGBA_UYVY
  • cv.COLOR_YUV2BGRA_Y422 = COLOR_YUV2BGRA_UYVY
  • cv.COLOR_YUV2RGBA_UYNV = COLOR_YUV2RGBA_UYVY
  • cv.COLOR_YUV2BGRA_UYNV = COLOR_YUV2BGRA_UYVY
  • cv.COLOR_YUV2RGB_YUY2 = 115
  • cv.COLOR_YUV2BGR_YUY2 = 116
  • cv.COLOR_YUV2RGB_YVYU = 117
  • cv.COLOR_YUV2BGR_YVYU = 118
  • cv.COLOR_YUV2RGB_YUYV = COLOR_YUV2RGB_YUY2
  • cv.COLOR_YUV2BGR_YUYV = COLOR_YUV2BGR_YUY2
  • cv.COLOR_YUV2RGB_YUNV = COLOR_YUV2RGB_YUY2
  • cv.COLOR_YUV2BGR_YUNV = COLOR_YUV2BGR_YUY2
  • cv.COLOR_YUV2RGBA_YUY2 = 119
  • cv.COLOR_YUV2BGRA_YUY2 = 120
  • cv.COLOR_YUV2RGBA_YVYU = 121
  • cv.COLOR_YUV2BGRA_YVYU = 122
  • cv.COLOR_YUV2RGBA_YUYV = COLOR_YUV2RGBA_YUY2
  • cv.COLOR_YUV2BGRA_YUYV = COLOR_YUV2BGRA_YUY2
  • cv.COLOR_YUV2RGBA_YUNV = COLOR_YUV2RGBA_YUY2
  • cv.COLOR_YUV2BGRA_YUNV = COLOR_YUV2BGRA_YUY2
  • cv.COLOR_YUV2GRAY_UYVY = 123
  • cv.COLOR_YUV2GRAY_YUY2 = 124
  • cv.COLOR_YUV2GRAY_Y422 = COLOR_YUV2GRAY_UYVY
  • cv.COLOR_YUV2GRAY_UYNV = COLOR_YUV2GRAY_UYVY
  • cv.COLOR_YUV2GRAY_YVYU = COLOR_YUV2GRAY_YUY2
  • cv.COLOR_YUV2GRAY_YUYV = COLOR_YUV2GRAY_YUY2
  • cv.COLOR_YUV2GRAY_YUNV = COLOR_YUV2GRAY_YUY2
  • cv.COLOR_RGBA2mRGBA = 125
  • cv.COLOR_mRGBA2RGBA = 126
  • cv.COLOR_RGB2YUV_I420 = 127
  • cv.COLOR_BGR2YUV_I420 = 128
  • cv.COLOR_RGB2YUV_IYUV = COLOR_RGB2YUV_I420
  • cv.COLOR_BGR2YUV_IYUV = COLOR_BGR2YUV_I420
  • cv.COLOR_RGBA2YUV_I420 = 129
  • cv.COLOR_BGRA2YUV_I420 = 130
  • cv.COLOR_RGBA2YUV_IYUV = COLOR_RGBA2YUV_I420
  • cv.COLOR_BGRA2YUV_IYUV = COLOR_BGRA2YUV_I420
  • cv.COLOR_RGB2YUV_YV12 = 131
  • cv.COLOR_BGR2YUV_YV12 = 132
  • cv.COLOR_RGBA2YUV_YV12 = 133
  • cv.COLOR_BGRA2YUV_YV12 = 134
  • cv.COLOR_BayerBG2BGR = 46
  • cv.COLOR_BayerGB2BGR = 47
  • cv.COLOR_BayerRG2BGR = 48
  • cv.COLOR_BayerGR2BGR = 49
  • cv.COLOR_BayerBG2RGB = COLOR_BayerRG2BGR
  • cv.COLOR_BayerGB2RGB = COLOR_BayerGR2BGR
  • cv.COLOR_BayerRG2RGB = COLOR_BayerBG2BGR
  • cv.COLOR_BayerGR2RGB = COLOR_BayerGB2BGR
  • cv.COLOR_BayerBG2GRAY = 86
  • cv.COLOR_BayerGB2GRAY = 87
  • cv.COLOR_BayerRG2GRAY = 88
  • cv.COLOR_BayerGR2GRAY = 89
  • cv.COLOR_BayerBG2BGR_VNG = 62
  • cv.COLOR_BayerGB2BGR_VNG = 63
  • cv.COLOR_BayerRG2BGR_VNG = 64
  • cv.COLOR_BayerGR2BGR_VNG = 65
  • cv.COLOR_BayerBG2RGB_VNG = COLOR_BayerRG2BGR_VNG
  • cv.COLOR_BayerGB2RGB_VNG = COLOR_BayerGR2BGR_VNG
  • cv.COLOR_BayerRG2RGB_VNG = COLOR_BayerBG2BGR_VNG
  • cv.COLOR_BayerGR2RGB_VNG = COLOR_BayerGB2BGR_VNG
  • cv.COLOR_BayerBG2BGR_EA = 135
  • cv.COLOR_BayerGB2BGR_EA = 136
  • cv.COLOR_BayerRG2BGR_EA = 137
  • cv.COLOR_BayerGR2BGR_EA = 138
  • cv.COLOR_BayerBG2RGB_EA = COLOR_BayerRG2BGR_EA
  • cv.COLOR_BayerGB2RGB_EA = COLOR_BayerGR2BGR_EA
  • cv.COLOR_BayerRG2RGB_EA = COLOR_BayerBG2BGR_EA
  • cv.COLOR_BayerGR2RGB_EA = COLOR_BayerGB2BGR_EA
  • cv.COLOR_BayerBG2BGRA = 139
  • cv.COLOR_BayerGB2BGRA = 140
  • cv.COLOR_BayerRG2BGRA = 141
  • cv.COLOR_BayerGR2BGRA = 142
  • cv.COLOR_BayerBG2RGBA = COLOR_BayerRG2BGRA
  • cv.COLOR_BayerGB2RGBA = COLOR_BayerGR2BGRA
  • cv.COLOR_BayerRG2RGBA = COLOR_BayerBG2BGRA
  • cv.COLOR_BayerGR2RGBA = COLOR_BayerGB2BGRA
  • cv.COLOR_COLORCVT_MAX = 143