Qfyilyi

I have made this algorithm myself based on how to rotate an image.

import cv2

import math

import numpy as np



class rotation:

    angle = 60.0

    x = 100

    y = 100

    img = cv2.imread('FNAF.png',0)

    width,height = img.shape

    def showImage(name, self):

        cv2.imshow(name, self.img)

    def printWidthHeight(self):

        print(self.width)

        print(self.height)

    def rotateImage(self):

        ForwardMap = np.zeros((self.width,self.height),dtype="uint8")

        BackwardMap = np.zeros((self.width,self.height),dtype="uint8")



        for i in range(self.width):

            for j in range(self.height):

                # forward mapping

                for_x = (i - self.x) * math.cos(self.angle*(math.pi/180)) - (j - self.y) * math.sin(self.angle*(math.pi/180)) + self.x

                for_y = (i - self.x) * math.sin(self.angle*(math.pi/180)) + (j - self.y) * math.cos(self.angle*(math.pi/180)) + self.x

                for_x = int(for_x)

                for_y = int(for_y)

                # backward mapping should change the forward mapping to the original image

                back_x = (i - self.x) * math.cos(self.angle*(math.pi/180)) + (j - self.y) * math.sin(self.angle*(math.pi/180)) + self.x

                back_y = -(i - self.x) * math.sin(self.angle*(math.pi/180)) + (j - self.y) * math.cos(self.angle*(math.pi/180)) + self.x

                back_x = int(back_x)

                back_y = int(back_y)

                if for_x in range(self.width) and for_y in range(self.height):

                    ForwardMap[i, j] = self.img[for_x, for_y]

                else:

                    pass

                if back_x in range(self.width) and back_y in range(self.height):

                    BackwardMap[i, j] = self.img[back_x, back_y]

                else:

                    pass

        cv2.imshow('Forward Mapping', ForwardMap)

        cv2.imshow('Backward Mapping', BackwardMap)

def demo():

    rotation.showImage('normal', rotation)

    rotation.printWidthHeight(rotation)

    rotation.rotateImage(rotation)

    cv2.waitKey(0)

    cv2.destroyAllWindows



if __name__ == '__main__':

    demo()

My problem is now that I want to make the rotated pictures (both for forward and backwards mapping) fit JUST right so there is no unnecessary use of space. Can anybody help me with this? Much appreciated.

If you have any suggestions to optimize my code, feel free to comment on that as well.

Your original image has 4 corners, coordinates: (0,0), (w-1, 0), (0,h-1) and (w-1, h-1). Since your transformation is affine, why not transform these coordinates into destination coordinates?

• (0,0) → (x1, y1)


• (w-1, 0) → (x2, y2)


• (0, h-1) → (x3, y3)


• (w-1, h-1) → (x4, y4)

Your destination image size is then:

width  = max(x1, x2, x3, x4) - min(x1, x2, x3, x4)

height = max(y1, y2, y3, y4) - min(y1, y2, y3, y4)