i1=round(i*cos(a) - j*sin(a)+ n * sin(a))+1
j1=round(i*sin(a) + j*cos(a))
这两个时会出现零值,那么,在MATLAB中索引F矩阵就是错误的了,你可以设置断点,然后单步运行一下看看在哪一步出现的零值,你根据旋转矩阵的计算应该是没有问题的,关键是灰度映射时可能出现零位置,最好在其中加入判断的语句,j1计算会出现0值。
你这样写,是沿坐标轴原点旋转,你说的我原来写的那个是沿固定点旋转,实现都是使用旋转矩阵,沿固定点只是先平移到原点,然后再平移回去,你可以看看,具体的我已经记不太清楚了,呵呵,已袜判尘经不做图像了。
我写的那个的程序:
function im_final = imrotate_my(im_path,theta,options)
%IM_ROTATE两维图像旋转以及双线性灰度插值算法的实现
%im_path 图像存储路径
%theta旋转角度告禅,正数表示顺时针旋转
%options 可以为circular(超出范围部分,按照周期形式扩展)
% crop(超出部分置零,即全黑)
%Ref. 章毓晋. 图像工程(上册)——图像处理. 清华大学出版社
%Author: lskypDate: 2009.08.12
%Version: V1.2 Original Version: V1.0 im_bilinear.mim_rotate.m
% with the parameter options added
error(nargchk(2,3,nargin,'string'))
if nargin == 2
options = 'circular'
else
if ~ (strcmp(options,'circular') || strcmp(options,'crop'))
error('错误的输出方法')
end
end
im_init = imread(im_path)
im_init = double(im_init)
im_height = size(im_init,1)
im_width = size(im_init,2)
% 分别处理灰度图像和RGB图像
if ndims(im_init) == 3
im_final = zeros(im_height,im_width,3)
R = im_init(:,:,1)
G = im_init(:,:,2)
B = im_init(:,:,3)
R_final = im_final(:,:,1)
G_final = im_final(:,:,2)
B_final = im_final(:,:,3)
else
im_final = zeros(im_height,im_width)
end
rot_matrix = [cos(theta) -sin(theta)sin(theta) cos(theta)]
orig_h = (im_height + 1)/2
orig_w = (im_width + 1)/2
for h = 1:im_height
for w = 1:im_width
% 平移至原点,冲岁旋转,然后再平移回去
new_position = rot_matrix*[h - orig_hw - orig_w] + [orig_horig_w]
% 超出范围按周期扩展控制,options参数控制
if strcmp(options,'circular')
new_position(1) = mod(new_position(1),im_height)
new_position(2) = mod(new_position(2),im_width)
if new_position(1) == 0
new_position(1) = im_height
end
if new_position(2) == 0
new_position(2) = im_width
end
end
% 如果新位置为整数,那么直接赋予灰度值或者RGB值,否则,按照双线性插值计算。
% 使用后向映射
if new_position == round(new_position)
if new_position(1) == 0
new_position(1) = 1
end
if new_position(2) == 0
new_position(2) = 1
end
% 超出范围控制,options为crop选项,超出范围置零
if strcmp(options,'crop') &&(new_position(1) >= im_height || ...
new_position(2) >= im_width || new_position(1) <0 || ...
new_position(2) <0)
if ndims(im_init) == 3
R_final(h,w) = 0
G_final(h,w) = 0
B_final(h,w) = 0
else
im_final(h,w) = 0
end
else
if ndims(im_init) == 3
R_final(h,w) = R(new_position(1),new_position(2))
G_final(h,w) = G(new_position(1),new_position(2))
B_final(h,w) = B(new_position(1),new_position(2))
else
im_final(h,w) = im_init(new_position(1),new_position(2))
end
end
else
h_new = floor(new_position(1))
w_new = floor(new_position(2))
if h_new == 0
h_new = 1
end
if w_new == 0
w_new = 1
end
% 超出范围控制,options为crop选项,超出范围置零
if strcmp(options,'crop') &&(h_new >= im_height || ...
w_new >= im_width || h_new <0 || ...
w_new <0)
if ndims(im_init) == 3
R_final(h,w) = 0
G_final(h,w) = 0
B_final(h,w) = 0
else
im_final(h,w) = 0
end
else
% 边界控制
h1 = h_new + 1
w1 = w_new + 1
if h1 >= im_height + 1
h1 = mod(h1,im_height)
end
if w1 >= im_width + 1
w1 = mod(w1,im_width)
end
if ndims(im_init) == 3
% 双线性插值的实现过程
% Ref. 章毓晋. 图像工程(上册)——图像处理. 清华大学出版社
R_temp1 = R(h1,w_new)*(new_position(1) - h_new) + ...
R(h_new,w_new)*(h_new + 1 - new_position(1))
R_temp2 = R(h1,w1)*(new_position(1) - h_new) + ...
R(h_new,w1)*(h_new + 1 - new_position(1))
R_final(h,w) = R_temp1*(w_new + 1 - new_position(2)) + ...
R_temp2*(new_position(2) - w_new)
G_temp1 = G(h1,w_new)*(new_position(1) - h_new) + ...
G(h_new,w_new)*(h_new + 1 - new_position(1))
G_temp2 = G(h1,w1)*(new_position(1) - h_new) + ...
G(h_new,w1)*(h_new + 1 - new_position(1))
G_final(h,w) = G_temp1*(w_new + 1 - new_position(2)) + ...
G_temp2*(new_position(2) - w_new)
B_temp1 = B(h1,w_new)*(new_position(1) - h_new) + ...
B(h_new,w_new)*(h_new + 1 - new_position(1))
B_temp2 = B(h1,w1)*(new_position(1) - h_new) + ...
B(h_new,w1)*(h_new + 1 - new_position(1))
B_final(h,w) = B_temp1*(w_new + 1 - new_position(2)) + ...
B_temp2*(new_position(2) - w_new)
else
gray_temp1 = im_init(h1,w_new)*(new_position(1) - h_new) + ...
im_init(h_new,w_new)*(h_new + 1 - new_position(1))
gray_temp2 = im_init(h1,w1)*(new_position(1) - h_new) + ...
im_init(h_new,w1)*(h_new + 1 - new_position(1))
im_final(h,w) = gray_temp1*(w_new + 1 - new_position(2)) + ...
gray_temp2*(new_position(2) - w_new)
end
end
end
end
end
if ndims(im_init) == 3
im_final(:,:,1) = R_final
im_final(:,:,2) = G_final
im_final(:,:,3) = B_final
end
im_final = im2uint8(mat2gray(im_final))
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