CODEWITHSUNDEEP
image-processingopencv
Rella
Rella

Reputation: 66935

How to fill OpenCV image with one solid color?

How to fill OpenCV image with one solid color?

Upvotes: 91

Views: 195112

Answers (9)

Kimmo
Kimmo

Reputation: 1956

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)

Upvotes: 45

Leox
Leox

Reputation: 370

color=(200, 100, 255) # sample of a color 
img = np.full((100, 100, 3), color, np.uint8)

Upvotes: 8

KAVYA SHARMA
KAVYA SHARMA

Reputation: 104

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)

Upvotes: 0

orangepips
orangepips

Reputation: 9961

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')

Upvotes: 9

Stéphane
Stéphane

Reputation: 20340

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

Upvotes: 14

Karthik N G
Karthik N G

Reputation: 2321

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

Upvotes: 4

Adi Shavit
Adi Shavit

Reputation: 17265

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));

Upvotes: 114

AlainD
AlainD

Reputation: 6597

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

Upvotes: 6

Barney Szabolcs
Barney Szabolcs

Reputation: 12514

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.

Upvotes: 11

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