- In MATLAB window, choose “Preferences.” Click “Image Processing” selection. In the “Border Style,” choose “Tight” instead of “Loose.” Click “OK.”
Required images: barbara.jpg, Lena.jpg, cameraman.jpg, lena_256.bmp
(a) Read the attached image “barbara.jpg” and display it. Hint commands: >> help imshow >> help imread
(b) Show the image information by typing imfinfo('barbara.jpg')
(c) Write the Barbara image into your hard disk with a name ‘barbara_mine.jpg.’ Read and display the saved image. Hint command: ‘help imwrite’.
(d) An image returned by “imread()” is an array of RGB color. Use Figures window, and under “Tools” select “Data Cursor”. Point the cursor to the location X: 92, Y:134, and tell what the RGB values are. Redo this as pointing the cursor to the location X:380, Y:300.
(e) How many rows, column, and channels of the Barbara image? Hint command: ‘help size’
(a) Convert the color image into grayscale (variable name img_gray). Save the grayscale image with a name “barbara_gray.png.” Show the grayscale image. Compare img_gray with img_gray2 that “img_gray2 = 0.2989 * img(:,:,1) + 0.5870 * img(:,:,2) + 0.1140 * img(:,:,3);” Hint command: ‘help rgb2gray’.
(b) Use whos to find out the size and class of variable ‘img’. Hint command: “help whos”.
(c) In each channel, how many bytes does a uint8 type pixel occupy? Convert the uint8 grayscale image into double type by “img_b=double(img_gray); imshow(img_b)”. What happen to the image and why it is displayed like that (please explain)? Note: click on the figure and choose a black box as the border for all white images, so we can see that a white image is enclosed.
(d) How many bytes does a double type pixel in each channel occupy? Convert the uint8 grayscale image into double type by function “im2double” or “img_b=double(img_gray)/255;” Display the double type grayscale image.
(a) Read the 512 x 512 Lena image as F and crop its center (row from 170 to 340 and column from 170 to 340) into a 171 x 171 (store in variable “Lena_center”). Show the cropped image.
(b) Add 100 to each pixel of Lena_center. Hint command: “help imadd”
(c) Multiply and divide each pixel of Lena_256 by 2, show both results.
(d) Read the 256 x 256 “cameraman.jpg” and crop its row from 1 to 171 and column from 1 to 171 into “cam_man” and add both “Lena_center” and “cam_man” together by function “imadd”. Show the combined image.
(a) Read the “lena_256.bmp” which is 256 x 256 resolution as variable lena. Change lena into a binary image, which has only two values: 0 and 1. Select the gray level which is greater than 200 or smaller than 100 to be 1 (white) and otherwise be 0 (black). Give the Matlab code and show the binary image.
(b) How to choose a suitable threshold value is a difficult job. Use the global image threshold by Otsu's method: graythresh, and use the function im2bw to change the grayscale image into a binary image by the Otsu’s threshold value. Show the binary image.
(c) Down-sample the grayscale lena 64 x 64 and up-sample it back to 256 x 256. Show three images: the original lena, the 64 x 64 lena, and the up-sampled 256 x 256. Hint command: “help imresize”
(d) Read lena_256.bmp, convolve the image with the mask
1/9 *
[1 1 1
1 1 1
1 1 1]
and show that it performs
averaging operation which results in blurring of the image. Also analyze the impact of increasing the
size of the mask to
5*5
. Provide your source code and
show the three images. Hint: use MATLAB functions “ones” to generate the matrix and use “conv2”
to do the convolution.
(a) Describe your previous BS/MS major and educational background.
(b) Describe your technical programming skills and languages used. Do you know Matlab programming? If not, you can start learning it by yourself from related books.
(c) State your previous courses, working experiences, and research projects that are relevant to image processing applications if you had before.
(d) There is a final research paper due in this course. You can choose any topic related to image processing and applications. You are required to read technical papers and write Matlab code to perform experiments and evaluations. What possible topic are you interested in pursuing this research?
