How to fill OpenCV image with one solid color

Question

User · Answer

Create a new 640x480 image and fill it with purple (red+blue):

cv::Mat mat(480, 640, CV_8UC3, cv::Scalar(255,0,255));

Note:

height before width
type CV_8UC3 means 8-bit unsigned int, 3 channels
colour format is BGR

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For an 8-bit  CV 8U  OpenCV image  the syntax is   Mat img Mat nHeight  nWidth  CV 8U   img   cv  Scalar 50         or the desired uint8 t value from 0-255

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Using the OpenCV C API with IplImage  img     Use cvSet    cvSet img  CV RGB redVal greenVal blueVal     Using the OpenCV C   API with cv  Mat img  then use either      cv  Mat  operator  const Scalar amp  s  as in     img   cv  Scalar redVal greenVal blueVal     or the more general  mask supporting  cv  Mat  setTo       img setTo cv  Scalar redVal greenVal blueVal

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The simplest is using the OpenCV Mat class   img cv  Scalar blue value  green value  red value     where img was defined as a cv  Mat

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color  200  100  255    sample of a color  img   np full  100  100  3   color  np uint8

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Here s how to do with cv2 in Python     Create a blank 300x300 black image image   np zeros  300  300  3   np uint8    Fill image with red color set each pixel to red  image       0  0  255    Here s more complete example how to create new blank image filled with a certain RGB color  import cv2 import numpy as np  def create blank width  height  rgb color  0  0  0           Create new image numpy array  filled with certain color in RGB          Create black blank image     image   np zeros  height  width  3   np uint8         Since OpenCV uses BGR  convert the color first     color   tuple reversed rgb color         Fill image with color     image      color      return image    Create new blank 300x300 red image width  height   300  300  red    255  0  0  image   create blank width  height  rgb color red  cv2 imwrite  red jpg   image

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Use numpy full  Here s a Python that creates a gray  blue  green and red image and shows in a 2x2 grid    import cv2 import numpy as np  gray img   np full  100  100  3   127  np uint8   blue img   np full  100  100  3   0  np uint8  green img   np full  100  100  3   0  np uint8  red img   np full  100  100  3   0  np uint8   full layer   np full  100  100   255  np uint8     OpenCV goes in blue  green  red order blue img       0    full layer green img       1    full layer red img       2    full layer  cv2 imshow  2x2 grid   np vstack       np hstack  gray img  blue img         np hstack  green img  red img       cv2 waitKey 0  cv2 destroyWindow  2x2 grid

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I personally made this python code to change the color of a whole image opened or created with openCV   I am sorry if it s not good enough   I am beginner    def OpenCvImgColorChanger img blue   0 green   0 red   0   line   1 ImgColumn   int img shape 0  -2 ImgRaw    int img shape 1  -2    for j in range ImgColumn        for i in range ImgRaw            if i    ImgRaw-1              line   1          img line  i  2    int red          img line  i  1    int green          img line  i  0    int blue

User · Answer

If you are using Java for OpenCV  then you can use the following code   Mat img   src clone      Clone from the original image img setTo new Scalar 255 255 255      This sets the whole image to white  it is R G B value

[image-processing] How to fill OpenCV image with one solid color?

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