回転せずに画像を回転（ポイント操作）

Image Rotation Without Imrotate

回転せずに画像を回転（ポイント操作）

The imrotate function is not used to achieve image rotation, the principle of which is to use point operation transformation to achieve. In general, when we realize image rotation, we first think of translating the center of rotation of the image to the origin of the upper left corner. After rotation and translation, we can get the rotated image. However, if we directly translate, rotate, and translate the original image, the new image is problematic. There will be many points in the new image that have no value, making the image like a honeycomb. Here we need to use reverse mapping, nearest neighbor interpolation (or bilinear interpolation) method to solve. Inverse mapping, nearest neighbor interpolation (or bilinear interpolation) (reference materials, self-understand): [https://blog.csdn.net/lkj345/article/details/50555870][1] [http://www.cnblogs.com/mlv5/archive/2012/02/02/2336321.html][2] [https://blog.csdn.net/glorydream2015/article/details/44873703][3] [https://www.cnblogs.com/linkr/p/3630902.html][4]

私のコードを添付してください：

% Image rotation

1. clear
2. clc
3. src = imread('1.png')
4. theta = 30
5. angle = 30 * pi / 180
6. figure
7. imshow(src)
8. % Original picturey xcorrespondingr c, After calculating the rotation angle of the new imager_new c_new, The angle will be negative when it is obtuse, so you need to addabs
9. [r,c,k] = size(src)
10. r_new = round(abs(r*cos(angle)) + abs(c*sin(angle)))
11. c_new = round(abs(r*sin(angle)) + abs(c*cos(angle)))
12. dst = zeros(r_new,c_new)% Construct a new image
13. dst1 = zeros(r_new,c_new)% Construct a new image
14. % Reverse mapping, the image is regarded as the translation, rotation, and translation of the new image to get the original image
15. % Instead of getting a new image from the original image translation rotation translation, this can solve the problem that some points are mapped to empty
16. translation1 = [1 0 -c_new/20 1 -r_new/20 0 1]% The center point of the new image is shifted to the origin in the upper left corner
17. rotate = [cos(angle) -sin(angle) 0sin(angle) cos(angle) 00 0 1]% Spinangleangle
18. translation2 = [1 0 c/20 1 r/20 0 1]% Pan back from origin
19. % Reverse mapping Match from each pixel of the new image
20. for i = 1:r_new
21. for j = 1:c_new
22. % Is mapped from the new image to the original image. If it is not in the original image, the new image is0, If it is, assign the nearest value to the point
23. P = translation2 * (rotate * (translation1* [ji1] ))%P(1)forxValue of P(2)foryValue of
24. if(round(P(1))>0 && round(P(1))<c && round(P(2))>0 && round(P(2))<r)
25. dst(i,j,1) = src(round(P(2)),round(P(1)),1)%takesrcNearest value of
26. dst(i,j,2) = src(round(P(2)),round(P(1)),2)
27. dst(i,j,3) = src(round(P(2)),round(P(1)),3)
28. else
29. dst(i,j) = 0
30. end
31. end
32. end
33. figure
34. imshow(dst/256)
35. title('Nearest Interpolation')
36. % Bilinear interpolation algorithm
37. for i = 1:r_new
38. for j = 1:c_new
39. % Is mapped from the new image to the original image. If it is not in the original image, the new image is0, If it is, assign the nearest value to the point
40. P = translation2 * (rotate * (translation1* [ji1] ))%P(1)forxValue of P(2)foryValue of
41. x = P(1)
42. y = P(2)
43. % Four points for bilinear interpolation
44. x_top = ceil(x)
45. x_bottom = floor(x)
46. y_top = ceil(y)
47. y_bottom = floor(y)
48. % Judgment conditions change accordingly
49. if(y_top < r && y_bottom >0 && x_bottom > 0 && x_top <c)
50. %m(i,j) = K(round(P(2,1)),round(P(1,1)))%yx
51. dst1(i,j,1) = src(y_bottom,x_bottom,1)*(x_top - x)*(y_top - y) + src(y_top,x_bottom,1)*(x_top - x)*(y - y_bottom) + src(y_bottom,x_top,1)*(x - x_bottom)*(y_top - y) + src(y_top,x_top,1)*(x - x_bottom)*(y - y_bottom)
52. dst1(i,j,2) = src(y_bottom,x_bottom,2)*(x_top - x)*(y_top - y) + src(y_top,x_bottom,2)*(x_top - x)*(y - y_bottom) + src(y_bottom,x_top,2)*(x - x_bottom)*(y_top - y) + src(y_top,x_top,2)*(x - x_bottom)*(y - y_bottom)
53. dst1(i,j,3) = src(y_bottom,x_bottom,3)*(x_top - x)*(y_top - y) + src(y_top,x_bottom,3)*(x_top - x)*(y - y_bottom) + src(y_bottom,x_top,3)*(x - x_bottom)*(y_top - y) + src(y_top,x_top,3)*(x - x_bottom)*(y - y_bottom)
54. else
55. dst1(i,j) = 0
56. end
57. end
58. end
59. figure
60. imshow(dst1/256)
61. title('Bilinear interpolation')

62. |_+_|