OctaveBildverarbeitung:tnotes

Revision [23025]

This is an old revision of OctaveBildverarbeitung made by ToBo on 2016-03-12 01:10:09.

Basic Image Processing with Octave

GNU Octave Version 3.0.5
Operating System: Linux 2.6.31-21-generic #59-Ubuntu SMP Wed Mar 24 07:28:56 UTC 2010 i686

Load an image

I = imread('kanu2010.jpg');

Check image size

whos I
ans =

   375   500     3

View images

show.m

figure(1);
subplot(1,2,1);
image(I/4);
axis off equal tight;
title('Original');
subplot(1,2,2);
image(J/4);
axis off equal tight;
title('Bearbeitet');

Better alternative to imshow():

show.m

figure(1);
subplot(1,2,1);
imshow(I/4);
title('Original');
subplot(1,2,2);
imshow(J/4);
title('Bearbeitet');

Image histogramm

[h,b,c] = size(I);
v = reshape(I, h*b*c,1,1);
figure(2);
hist(v,256/5)

Example 1

Reduce brightness by -50 steps
Increase contrast by +30 %
J=(I-50)*1.3;

Example 2

Reduce green channel by 50 %

J=I;J(:,:,2)=J(:,:,2)/2;

Example 3

Calculate gray image

J=fix(I); % uint8 in real umwandel
J(:,:,1)=(J(:,:,1)+J(:,:,2)+J(:,:,3))/3; % Mittelwert aus allen Kanälen
J(:,:,2)=J(:,:,1); % Kanal kopieren
J(:,:,3)=J(:,:,1); % Kanal kopieren

Example 4

Copy green channel to red channel. Green and blue channels stay untouched.

J=I;J(:,:,1)=I(:,:,2);

Example 5

Exchange green and blue channels. ;-)

J=I;J(:,:,2)=I(:,:,3);J(:,:,3)=I(:,:,2);

Example 6

Blur image using a simple low-pass filter.

J=I; for c=1:3; J(:,:,c) = filter2(ones(5,5)/25,fix(I(:,:,c)));end

Example 7

Detect edges and add the edges to the original image, giving the image more sharpeness.

J=I;
for c=1:3; J(:,:,c) = filter2(ones(5,5)/25,fix(I(:,:,c)));end
J=(I-J)*1.5;
J=I+J;

Example 8

Generate a black and white image. Just two colors: white and black!

Load another image.

I = imread('andreas.jpg');

First generate a gray image.

J=fix(I); % uint8 in real umwandeln
J(:,:,1)=(J(:,:,1)+J(:,:,2)+J(:,:,3))/3; % Mittelwert aus allen Kanälen
J(:,:,2)=J(:,:,1); % Kanal kopieren
J(:,:,3)=J(:,:,1); % Kanal kopieren

Now, calculate a threshold and generate the black and white image.

J=((K+77)>128)*255; % SW-Bild erzeugen

Calculate the percentage of white pixels.

[n,m]=size(J);length(find(J>128))/(n*m)*100

White pixels: 78 %

Example 9

Generate a three color image using only black, red and yellow colors.

J(:,:,1)=((K(:,:,1)+77)>128)*255;show;
J(:,:,2)=((K(:,:,2)+60)>128)*255;show;
J(:,:,3)=((K(:,:,3)+47)>128)*255;show;

Example 10

Special effects ;.)

J=-sin(I/25)*128+128;

Example 11

Edge detector according to an algorithm by Rachid Deriche.

for k=1:3; J(:,:,k)=deriche(I(:,:,k),2,0)*4;end ;

BildRaetsel

Siehe auch

tnotes : OctaveBildverarbeitung