Lab 1. Basic Image Processing Algorithms Fall 2017

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1 Lab 1 Basic Image Processing Algorithms Fall 2017

2 Lab practices - Wednesdays 8:15-10:00, room 219: excercise leaders: Csaba Benedek, Balázs Nagy instructor: Péter Bogdány 8:15-10:00, room 220: excercise leader: Miklós Koller instructor: Ágnes Szabó 10:15-12:00, room 422: excercise leader: Márton Bese Naszlady instructor: Bendegúz Tamás Módli 2

3 Lab practices - requirements the attendance is obligatory; there will be a programming task that you have to complete and submit to an SVN server; you have to understand your code and be able to explain it; if you are unable to finish until the end of the lab practice, you have to finish it at home and submit before the next Tuesday s 23:59; (except today) submitting all tasks in time is a requirement of passing the course. To have account on the SVN server: please fill the following form NOW: 3

4 Lab 1: revising MATLAB 7 exercises will be given; the usage of these matlab commands should be confident during the rest of the semester. The SVN repository will be created at the beginning of the next week: please bring your solution of Lab1 with yourself to the next class (next lab, 27 Sept.), and we will upload it together to the SVN server. To have SVN-client at home: please install Tortoise SVN. 4

5 Test images for the course All of the test images used for the following tasks can be found at: 5

6 Exercise 1 Create a function that: reads in a colored image (use imread()), displays it with imshow(), check if the input image has 3 channels (use size()), converts it to grayscale (use rgb2gray()), displays the grayscale image, save the gray image (with imwrite()), the parameters of this function should be as follows: input1: path to the image file; input2: output file path; output: grayscale image (as an array). Create a script that: calls the previously written function with the appropriate parameters (eg. AlfredoBorba_TuscanLandscape.jpg), displays with imshow() the returned image. 6

7 Exercise 2 Create a function that: reads in a colored image, rotates it with 45 degrees (imrotate), flips the image vertically (flipud), flips the image horizontally (fliplr), saves all the images (name is the original name with postfix, use fileparts), before saving check the existence of the output dir (exist(some_path, 'dir')), parameters: input1: path to the image file, input2: absolute path of the output folder, output1: array of the rotated image, output2: array of the vertically flipped image, output3: array of the horizontally flipped image. 7

8 Exercise 2 Create a script that: calls the previously written function with the appropriate parameters, displays the returned images in one figure, with multiple subplot-s (output parameters): 8

9 Exercise 3 Create a function that: reads in a colored image, mixes up channel R with channel B (do it pixel-by-pixel with a for loop), measures the runtime with tic/toc, and prints it with disp, saves the image (name is the original name with postfix, use fileparts), parameters: input1: path to the image file, input2: absolute path of the output folder, output1: array of the mixed up image, implements the channel mix-up without for loop (think about the colon operator : at the array-indexing), and measure the runtime again. 9

10 Exercise 3 Create a script that: calls the previously written function with the appropriate parameters, displays the returned image: 10

11 Exercise 4 Create a function that: reads in an image, converts it to grayscale if necessary, binarizes the image with a threshold (each pixel above the threshold will become white and the others black), saves the image with an appropriate postfix, parameters: input1: path to the image file, input2: absolute path of the output folder, input3: threshold (if there is no 3rd input use the mean intensity level as threshold; to check the input parameters use varargin), output1: binary image. Create a script that: calls the previously written function with the appropriate parameters, displays the returned image. 11

12 Exercise 5 Create a function that: reads in an image, converts it to grayscale if necessary, creates a 10 pixel wide border for the image: create a matrix that is 20 pixel larger in both dimensions (use ones()), and place the image in the middle, saves the image with an appropriate postfix, parameters: input1: path to the image file, input2: absolute path of the output folder, output1: array of the framed image. Create a script that: calls the previously written function with the appropriate parameters, displays the returned image. 12

13 Exercise 6 Create a function that: reads in an image, converts it to grayscale if necessary, displays the image in the upper subplot of a figure, plots the pixel intensity values of the i-th row of the image (use plot function) in the lower subplot of a figure, puts labels on the axis (xlabel, ylabel, title), saves the figure (saveas) with an appropriate postfix, parameters: input1: path to the image file, input2: absolute path of the output folder, input3: value of i (which row to plot), input4: optionally index for an other row --- plot this other row as well with a different color, use hold on/off and varargin, no output. 13

14 Exercise 6 Create a script that: calls the previously written function with the appropriate parameters. 14

15 Exercise 7 Create a function that: reads in 2 images, converts them to grayscale if necessary, converts them into the same size (imresize), creates a 3D array of one image fading into the other (3rd dim: time), parameters: input1: path to the first image file, input2: path to the second image file, input3: number of frames to create, output: the 3D transition array At the generation of the individual frames, you have to think about the type-conversions (double, uint8). 15

16 Exercise 7 Create a script that: calls the previously written function with the appropriate parameters, displays the video with the built-in implay() function. 16

Matlab for CS6320 Beginners

Matlab for CS6320 Beginners Basics: Starting Matlab o CADE Lab remote access o Student version on your own computer Change the Current Folder to the directory where your programs, images, etc. will be