How to fill OpenCV image with one solid color?

问题:

How to fill OpenCV image with one solid color?

回答1:

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& 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));

回答2:

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)

回答3:

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.

回答4:

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

回答5:

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

回答6:

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

回答7:

Use numpy.full. Here's a Python example that sets the whole image to gray and ensures an unsigned 8-bit integer result type.

import cv2
import numpy as np
img = np.full((100, 100, 3), 127, np.uint8) 
cv2.imshow('single color', img)
cv2.waitKey(0)
cv2.destroyWindow('single color')