magnitude and direction

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munch kitty
munch kitty 2012-2-6
回答： ANIMA V A 2015-11-24
how to calculate the magnitude and direction value of the images in matlab?(code)
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Qura
Qura 2013-3-29
Hi! I want to construct histogram of gradient magnitude and gradient direction for each image gradient.angle are quantized by 45 Please help
Walter Roberson
Walter Roberson 2013-3-29
Please start a new Question for this problem.

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回答（3 个）

Junaid
Junaid 2012-2-6
what do you mean by direction of images. I hope you are talking about gradient value and direction (orientation) ?
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Rupali
Rupali 2012-2-6
i want to know how to divide image into blocks ????????
munch kitty
munch kitty 2012-2-8
a=imread('image004.png'); a1=imresize(a,[300,340]);
cbs=100;
ck1=1; cblock(:,:,:,1)=a1(1:100,1:100,:);
cblock(:,:,:,5)=a1(101:200,1:100,:);
cblock(:,:,:,9)=a1(201:300,1:100,:);
for ci1=1:3
ck1=ck1+1;
for cj1=1:3
row1=80 ;
row2=180;
cblock(:,:,:,ck1)=a1( (cbs*(ci1-1)+1:cbs*(ci1-1)+cbs), ((row1+1)+(cj1-1)*80:row2+(cj1-1)*80),:);
ck1=ck1+1;
end
end
we divide the image into 3X4.overlap of some pixels..u can also do non overlapping..

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Junaid
Junaid 2012-2-6
I think you want to compute the SIFT right ?
Anyway to divide the image into blocks, you can use following tip
http://mathworks.com/matlabcentral/answers/24104-image-separation-into-blocks
in case you have difficulty you can share your code.
To find the gradient magnitude and orientation, the following code may help you.
angle = 360;
[GradientX,GradientY] = gradient(double(img));
Gr = sqrt((GradientX.*GradientX)+(GradientY.*GradientY));
index = GradientX == 0;
GradientX(index) = 1e-5;
YX = GradientY./GradientX;
A = ((atan2(GradientY,GradientX)+pi)*180)/pi;
A contains the orientation of each pixel.
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mano
mano 2012-2-8
i found the gradient and magnitude but i want to how to found gradient magnitude histogram?if u know help me
Lee
Lee 2013-3-25
Hi Junaid, may I know why parameter YX is calculated?

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ANIMA V A
ANIMA V A 2015-11-24
How to compute gradient in three different directions? Can any one help me i need to compute the gradient in 3 different directions for an image please help me

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