Rotate an Image Without Using OpenCV

• Step1: The first step is to convert degree to radian as NumPy takes radian as input.
• Step2: Defined new Image(canvas) size which is dynamic. As the new image dimension will change as part of the rotation process.
• Step3: Start applying logic to rotate from the image midpoint.
  • Once, the image mid-point is identified, start applying rotation logic
  • Adjust the new rotation point with respect to the canvas image.
  • Check if the new points do not cross the defined canvas size (row and columns)
• Step4: Plot images

import numpy as np
import math
import pylab
from PIL import Image
import matplotlib.pyplot as plt

class ICV_RotateImage:
    #Rotate an Image without using OpenCV
    def __init__(self):
        pass

    def ICV_degreeToRadian(self, degree):
        '''
        Convert degree to radian
        :param degree: degree
        :return: radian
        '''
        return (degree * np.pi) / 180.0


    def ICV_getImageMidPoints(self, image):
        '''
        This method returns image midpoints
        :param image:
        :return: x_mid, y_mid
        '''
        height, width, num_channels = image.shape
        y_mid = height / 2
        x_mid = width / 2
        return x_mid, y_mid

    '''
    rotate image in python
    '''
    def ICV_rotateImageBasedOnDegree(self, image, degree):
        '''
        Rotate image based on degree
        :param image: actual image
        :param degree: degree
        :return: rotated image
        '''
        radian = self.ICV_degreeToRadian(degree)
        x_mid, y_mid = self.ICV_getImageMidPoints(image)

        newimage = self.ICV_canvasSize(image)

        newimage_x_mid, newimage_y_mid = self.ICV_getImageMidPoints(newimage)
        print("New image midpoint:newimage_x_mid",newimage_x_mid ,"newimage_y_mid" , newimage_y_mid )

        for img_x in range(image.shape[0]):
            for img_y in range(image.shape[1]):
                # This will start with midpoints in first iteration
                # and then propagates back
                y_prime = y_mid - img_y
                x_prime = x_mid - img_x

                x_new = (x_prime) * math.cos(radian) - (y_prime) * math.sin(radian) #Rotate an Image without using OpenCV
                y_new = (x_prime) * math.sin(radian) + (y_prime) * math.cos(radian)

                # Adjust each new points wrt newImage mid points
                xdist = int(newimage_x_mid - x_new)
                ydist = int(newimage_y_mid - y_new)
                if (xdist < newimage.shape[0]) and ydist < newimage.shape[0]:
                    newimage[xdist][ydist][:] = image[img_x][img_y][:]


        return newimage


    def ICV_canvasSize(self, image):
        '''
        This method generates Canvas Size based on Input Image
        :param image: image array
        :return: canvas
        '''
        height, width, num_channels = image.shape
        max_len = int(math.sqrt(width * width + width * width))
        canvas = np.zeros((max_len, max_len, 3))
        return canvas


    def ICV_plotImage(self, newImage):
        '''
        This method plots the new image
        :param newImage:
        :return: Null
        '''
        plt.gca().set_axis_off()
        plt.margins(0, 0)
        plt.gca().xaxis.set_major_locator(plt.NullLocator())
        plt.gca().yaxis.set_major_locator(plt.NullLocator())

        output_image = Image.fromarray(newImage.astype("uint8"))
        plt.imshow(output_image)
        plt.savefig("output_image_rotate.jpg",bbox_inches='tight', pad_inches=0)
        plt.show()


def main():
    image = Image.open('image1.jpg')
    image = np.asarray(image)
    print(image.shape)
    rotation = ICV_RotateImage() ## Create an Object

    newImage1 = rotation.ICV_rotateImageBasedOnDegree(image, 30)
    rotation.ICV_plotImage(newImage1)

#main method to Rotate an Image without using OpenCV
if __name__ == "__main__":
    main()

Output:

In this blog, you learned about how to rotate an image without using OpenCV, and follow the code to rotate images in python using python. Please comment below in case of any doubts.

#rotate images in python