Image Rotation Using Matrix Transformation

About Program

This program can rotate any images by any angle using matrix transformation(matrix multiplication operation). To run the program, you need to install numpy and opencv for python.

	import numpy
	import cv2
	import math
	def img_rot(src_image, deg):
	#convert from degress to radians
	rad = math.radians(deg)
	#store value of source image height and width
	src_h, src_w = src_image.shape[0], src_image.shape[1]
	mid_x_src, mid_y_src = src_w//2, src_h//2
	#calculate value of output image height and width
	out_h = round(abs(src_w*math.sin(rad)) + abs(src_h*math.cos(rad)))
	out_w = round(abs(src_w*math.cos(rad)) + abs(src_h*math.sin(rad)))
	#calculate mid point to use as origin
	mid_x_out, mid_y_out = out_w//2, out_h//2
	out_image = numpy.uint8(numpy.zeros((out_h, out_w, src_image.shape[2])))
	for i in range(src_h):
	for j in range(src_w):
	#transformation and rotation
	x = round((j-mid_x_src) * math.cos(rad) + (i-mid_y_src) * math.sin(rad))
	y = round(-(j-mid_x_src)*math.sin(rad) + (i-mid_y_src)*math.cos(rad))
	#transform back
	x += mid_x_out
	y += mid_y_out
	#check if in bound
	if 0 <= x < out_w and 0 <=y <out_h:
	out_image[y][x] = src_image[i][j]
	#this block of code is similar to the top block. it is used to fill out the hole when there is error from converting from float to int
	for i in range(out_h):
	for j in range(out_w):
	x = round((j-mid_x_out) * math.cos(rad)-(i-mid_y_out)*math.sin(rad))
	y = round((j-mid_x_out)* math.sin(rad) + (i-mid_y_out)* math.cos(rad))
	x += mid_x_src
	y += mid_y_src
	if 0 <= x < src_w and 0 <= y < src_h:
	out_image[i][j] = src_image[y][x]
	return out_image
	#main
	#you can put any image you want
	src_image = cv2.imread("sunflower.jpg")
	#in this case 120 is the angle of rotation
	out_image = img_rot(src_image, 120)
	#output new image
	cv2.imwrite("new_sunflower2.jpg", out_image)
	print("Success!")

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Github Repo

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