Objective: To learn the basic operations related to image acquisition
Question 1:
a) Copy image, 'Porsche.tiff' into any directory. Example; C:\Users\abc\Desktop. Also can use another pictures. Read the file. How large is the image (rows, columns)?
Porsche.tiff
Answer:
- Use command imread to read the file. Refer to Lab 1 in previous entry (click here).
- Before that, make sure your current directory in Matlab is the same as the location of the image ('Porsche.tiff') that have been saved. Example; C:\Users\abc\Desktop
>> I=imread('Porsche.tiff')
To check how large is the image (rows and columns), go to Matlab workspace.
Value = <342x546 uint8>
Rows = 342
Columns = 546
Or, double click (open I) I in workspace.
Variable editor of I will be displayed.
You can scroll the scroll bar to check the rows and columns.
b) Answer the following questions about the image:
How big is the file (bytes)?
- Use whos command
>> whos
Answer: 186732 Bytes
- How large is the image (rows, columns)?
Answer: Rows = 342, Columns = 546
- What are the minimum and maximum grey values?
Check at workspace.
Answer: Min = 0, Max = 240
Question 2
Part I: Image Acquisition
- Use your own picture.
baby.jpg
Part II: Read the image into Matlab
- Use imread command to read the image you have acquired in Part I.
>> I=imread('baby.jpg')
- Display the information of matrix I.
>> whos
The class should be "uint8" and the third dimension of I should be 3, which denotes it is a color image (the three components correspond to R,G,B channels respectively - e.g; blue channel is given by I(:,:,3).
- Display image to see the original colour.
>>imshow(I)
- Convert the image into grayscale.
>> I2 = I(:,:,3);
Then, display the new I2 to see how the image converted into grayscale mode.
>> imshow(I2)
- Display the green channel of the image.
Use grayscale image (I2).
>> figure, imshow(I2),colormap([zeros(256,1),[0:1/255:1]',zeros(256,1)]),colorbar
*Additional task - convert into red channel.
>> figure, imshow(I2),colormap([[0:1/255:1]', zeros(256,1),zeros(256,1)]),colorbar
Part III: Basic Image Operations
-Transport the image and display it.
>> I3=ctranspose(I2);
>> imshow(I3)
- Crop the top-left quarter of the image and display it.
>> I4 = imcrop(I,[60 40 80 90]);
>> imshow(I4)
- Flip the image left to right and display it.
>> I5 = fliplr(I2);
>> imshow(I5)
