Examples and Webinars - Image Processing Toolbox for MATLAB & Simulink1

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Podc & Seice > Image Poceing Toolbo > Eample and Webina

Image Processing Toolbo

Eamples and Webinars

Finding the Rotation and Scale of a Distorted Image

If o kno ha one im age i dioed elaie o anohe onl b a oaion and cale change, o can e cp2fom

o find he oaion angle and cale faco. Yo can hen anfom he di oed image o ecoe he oiginal im age.

Contents

Sep 1: Read Image

Sep 2: Reie he Image

Sep 3: Roae he Image

Sep 4: Selec Conol Poin

Sep 5: Infe Tanfom

Sep 6: Sole fo Scale and Angle

Sep 7: Recoe Oiginal Image

Step 1: Read Image

Bing o faoie image ino he okpace.

I = imead('cameaman.if');

imho(I);

e(ie(I,2),ie(I,1)+15, ...

'Image coe of Maache Inie of Technolog', ...

'FonSie',7,'HoionalAlignmen','igh');

Step 2: Resie the Image

cale = 0.6;

J = imeie(I,cale); % T aing he cale faco.

Step 3: Rotate the Image

hea = 30;

K = imoae(J,hea); % T aing he angle, hea.

TRY OR BU

Conac Sale

Podc Tia

Picing and

Acceleaing he pace of engineeing and cience


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fige, ih(K)

Step 4: Select Control Points

Ue he Conol Poin Selecion Tool o pick a lea o pai of conol poin.

i_i = [129.87 141.25; 112.63 67.75];

bae_i = [135.26 200.15; 170.30 79.30];

Yo can n he e of he demo ih hee pe-picked poin, b picking o on poin o ee ho he e l

a.

ceec(K,I,i_i,bae_i);

Sae conol poin b chooing he File men, hen he Sae Points to Workspace opion. Sae he poin,

oeiing aiable i_i and bae_i.

Step 5: Infer Transform

Find a TFORM ce ha i conien ih o conol poin .

= c2f(i_i,bae_i,'efecie iiai');

Afe o hae done Sep 6 and 7, epea Sep 5 hogh 7 b ing 'affine' inead of 'noneflecie imilai'.

Wha happen? Ae he el a good a he ee ih 'noneflecie imilai'?

Step 6: Sole for Scale and Angle

The TFORM ce,, conain a anfomaion m ai in .daa.Ti. Since o kno ha he anfomaion

inclde onl oaion and caling, he mah i elaiel im ple o ecoe he cale and angle.

Le c = *c(hea)

Le = *i(hea)

The, Ti = .daa.Ti = [c - 0;

c 0;

1]

hee ad ae ad aai, eecie.

= .daa.Ti(2,1);

c = .daa.Ti(1,1);

cae_eceed = (* + c*c)

hea_eceed = aa2(,c)*180/i

scale_recoered =


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0.6000

theta_recoered =

29.3699

The ae fscale_recovered hd be 0.6 haeescale ed i Step 2: Resie the Image . The ae

ftheta_recovered hd be 30 haeetheta ed i Step 3: Rotate the Image.

Step 7: Recover Original Image

Rece he igia i age b afig K, he aed-ad-caed iage, ig TFORM ce t ad ha

ab he ie fI.

I he recovered iage, ice ha he ei i a gd a i he igia iage I. Thi i de he

eece hich icded hiig-ad-aig he gig-ad-aig. Shiig edce he be f ie

i he iage K i effecie ha e ifai ha he igia i age I.

The aifac ad he edge ae de he i ied accac f he afai. If ee ic e i

i Step 4: Select Control Points, he afai d be e accae.

D = sie(I);

recovered = imtransform(K,t,'XData',[1 D(2)],'YData',[1 D(1)]);

% Compare recovered to I.

figure, imshow(I)

title('I')

figure, imshow(recovered)

title('recovered')


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Examples and Webinars - Image Processing Toolbox for MATLAB & Simulink1

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