help ! how do i fix this error : Error using .* Integers can only be combined with integers of the same class, or scalar doubles.

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yen hsun lee
yen hsun lee on 14 Apr 2022
Commented: yen hsun lee on 23 Apr 2022
clear;clc;
im=imread(' image.png');
R=im(:,:,1);
G=im(:,:,2);
B=im(:,:,3);
Y=0.299*R + 0.587*G + 0.114*B;
im = im2double(rgb2gray(im));
[~, T]=graythresh(im);
bwImage=imbinarize(im,T);
[M,~] = size(im);
[label,num] = bwlabel(im);
coor = zeros(num,2);
for n = 1:num
[x,y] = find(label==n);
m_iN = length(x);
for k = 1:m_iN
pSrc(k) = Y(x(k),y(k));
tmp_B(k,1) = x(k)^2;
tmp_B(k,2) = y(k)^2;
tmp_B(k,3) = x(k);
tmp_B(k,4) = y(k);
tmp_B(k,5) = 1;
end
[Q R]=qr(tmp_B);
pSrc=pSrc';
S = Q'*pSrc;
S = S(1:5);
R1 = R(1:5,1:5);
C = R1\S;
coor(n,:) = [-0.5*C(1)/C(3),-0.5*C(2)/C(4)];
end

Answers (4)

KSSV
KSSV on 14 Apr 2022
Read about class. To multiply two variables, they should be of same class.
a = int8(6) ;
b = int16(6) ;
c = int8(6) ;
class(a)
ans = 'int8'
class(b)
ans = 'int16'
class(c)
ans = 'int8'
a*c % no error
ans = int8 36
a*int8(b) % no error, class int16 converted to class int8
ans = int8 36
a*b % error
Error using *
Integers can only be combined with integers of the same class, or scalar doubles.

Walter Roberson
Walter Roberson on 14 Apr 2022
The code you posted does not contain any .* operations, unless inside one of the calls.
But
S = Q'*pSrc;
If I scan correctly, Q is double precision but pSrc is uint8.
Y=0.299*R + 0.587*G + 0.114*B;
R G B are all uint8, and double times array of uint8 gives uint8, so Y will be uint8. Later you copy values out of Y into pSrc without having initialized pSrc so the uint8 type will be copied so pSrc will be uint8.

Bruno Luong
Bruno Luong on 14 Apr 2022
Add cast to double statement after reading your image
im=imread(' image.png');
im = double(im);
...

yanqi liu
yanqi liu on 19 Apr 2022
im=imread('football.jpg');
im=imresize(im,20/size(im,1),'bilinear');
R=im(:,:,1);
G=im(:,:,2);
B=im(:,:,3);
Y=0.299*R + 0.587*G + 0.114*B;
im = im2double(rgb2gray(im));
[~, T]=graythresh(im);
bwImage=imbinarize(im,T);
[M,~] = size(im);
[label,num] = bwlabel(im);
coor = zeros(num,2);
for n = 1:num
[x,y] = find(label==n);
m_iN = length(x);
for k = 1:m_iN
pSrc(k) = Y(x(k),y(k));
tmp_B(k,1) = x(k)^2;
tmp_B(k,2) = y(k)^2;
tmp_B(k,3) = x(k);
tmp_B(k,4) = y(k);
tmp_B(k,5) = 1;
end
[Q, R]=qr(tmp_B);
pSrc=pSrc';
S = double(Q')*double(pSrc);
S = S(1:5);
R1 = R(1:5,1:5);
C = R1\S;
coor(n,:) = [-0.5*C(1)/C(3),-0.5*C(2)/C(4)];
end
coor
coor = 1×2
0.0256 0.0199

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