Learn to Program with Kotlin: From the Basics to Projects with Text and Image Processing

373 Pages·2021·8.272 MB·English

by  Tim Lavers

Learn to
Program
with Kotlin
From the Basics to Projects with
Text and Image Processing
—
Tim Lavers
Learn to Program
with Kotlin
From the Basics to Projects with Text
and Image Processing
Tim Lavers
Learn to Program with Kotlin: From the Basics to Projects with Text and
Image Processing
Tim Lavers
Woonona, NSW, Australia
ISBN-13 (pbk): 978-1-4842-6814-8 ISBN-13 (electronic): 978-1-4842-6815-5
https://doi.org/10.1007/978-1-4842-6815-5
Copyright © 2021 by Tim Lavers
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Printed on acid-free paper
Table of Contents
About the Author �����������������������������������������������������������������������������������������������������xi
About the Technical Reviewer �������������������������������������������������������������������������������xiii
Preface ��������������������������������������������������������������������������������������������������������������������xv
Part I: Basics ��������������������������������������������������������������������������������������������������1
Chapter 1: Getting Started ����������������������������������������������������������������������������������������3
1.1 What Is Programming? ............................................................................................................3
1.2 Installing Java .........................................................................................................................4
1.3 Installing Git ............................................................................................................................4
1.4 Installing IntelliJ ......................................................................................................................5
1.5 Our First Program ....................................................................................................................5
1.6 Changing the Appearance of IntelliJ .......................................................................................7
1.7 Troubleshooting .......................................................................................................................8
1.8 Running Our First Program .....................................................................................................8
1.9 Source Code for Our Program .................................................................................................9
Chapter 2: Simple Patterns �������������������������������������������������������������������������������������13
2.1 Shades of Gray ......................................................................................................................13
2.2 Changing the Pattern ............................................................................................................15
2.3 Solutions to Challenges ........................................................................................................18
Chapter 3: Arrays and Loops ����������������������������������������������������������������������������������21
3.1 Array Indexes ........................................................................................................................21
3.2 Loops ....................................................................................................................................24
3.3 Nested Loops ........................................................................................................................27
3.4 Summary and Solutions to Challenges .................................................................................28
iii
Table of ConTenTs
Chapter 4: Binary Choices ��������������������������������������������������������������������������������������33
4.1 If-Else Statements ................................................................................................................33
4.2 The Or Operator .....................................................................................................................37
4.3 The And Operator ..................................................................................................................40
4.4 If-Else-If Statements .............................................................................................................41
4.5 Summary and Solutions to Challenges .................................................................................44
Chapter 5: Integers �������������������������������������������������������������������������������������������������49
5.1 Addition, Subtraction, and Multiplication ..............................................................................49
5.2 Division .................................................................................................................................54
5.3 Making Patterns Using Arithmetic ........................................................................................55
5.4 Summary and Solutions to Challenges .................................................................................59
Chapter 6: Values and Variables �����������������������������������������������������������������������������65
6.1 Using vars ............................................................................................................................65
6.2 Using vals ............................................................................................................................67
6.3 Scope ....................................................................................................................................69
6.4 Summary and Solutions to Challenges .................................................................................71
Chapter 7: Strings ���������������������������������������������������������������������������������������������������75
7.1 Strings as Objects .................................................................................................................75
7.2 String Iteration ...................................................................................................................78
7.3 Building New Strings .........................................................................................................80
7.4 More on String Iteration .....................................................................................................82
7.5 Summary and Solutions to Challenges .................................................................................84
Chapter 8: Data Structures �������������������������������������������������������������������������������������91
8.1 Lists ......................................................................................................................................91
8.2 Sets .......................................................................................................................................93
8.3 Maps .....................................................................................................................................94
8.4 null Objects .........................................................................................................................95
8.5 Summary and Solutions to Challenges .................................................................................99
iv
Table of ConTenTs
Chapter 9: The File System �����������������������������������������������������������������������������������101
9.1 Reading ...............................................................................................................................102
9.2 Writing .................................................................................................................................104
9.3 Summary and Solutions to Challenges ...............................................................................106
Part II: Text �������������������������������������������������������������������������������������������������109
Chapter 10: Project Austen �����������������������������������������������������������������������������������111
10.1 Object-Oriented Programming ..........................................................................................111
10.2 Unit Tests...........................................................................................................................112
10.3 Project Structure and Setup ..............................................................................................112
10.4 LineTest and Line ..............................................................................................................114
10.5 Further Tests of Line ........................................................................................................122
10.6 HistogramTest and Histogram ...........................................................................................125
10.7 BookTest and Book ...........................................................................................................133
10.8 Back to LineTest and Line ............................................................................................138
10.9 Testing with Real Data ......................................................................................................142
10.10 Almost Finished ...............................................................................................................143
10.11 Counting the Words .........................................................................................................148
10.12 Putting Things in Order ...................................................................................................150
10.13 Taking Things Further ......................................................................................................155
10.14 Summary.........................................................................................................................156
Chapter 11: Anagrams ������������������������������������������������������������������������������������������157
11.1 Main Classes .....................................................................................................................157
11.2 The Dictionary Class .....................................................................................................159
11.3 The Term Class .................................................................................................................164
11.4 Permutations .....................................................................................................................165
11.5 The permutations Function ...........................................................................................165
11.6 G enerating the Permutations of a Term ............................................................................169
11.7 Putting It All Together ........................................................................................................180
11.8 Summary...........................................................................................................................183
v
Table of ConTenTs
Chapter 12: Palindromes ��������������������������������������������������������������������������������������185
12.1 Reversing a Term ..............................................................................................................185
12.2 Detecting Palindromes ......................................................................................................189
12.3 Putting It All Together ........................................................................................................190
12.4 Summary...........................................................................................................................193
Chapter 13: Word Switch ��������������������������������������������������������������������������������������195
13.1 The Algorithm ....................................................................................................................195
13.1.1 Generation 1 ............................................................................................................. 195
13.1.2 Generation 2 ............................................................................................................. 196
13.1.3 Generation 3 ............................................................................................................. 196
13.1.4 Generation 4 ............................................................................................................. 196
13.1.5 Algorithm Termination with Success ........................................................................196
13.1.6 Algorithm Termination with Failure...........................................................................197
13.2 Main Classes and Project Setup .......................................................................................197
13.3 The WordChecker Class ...................................................................................................198
13.4 The WordNode Class .........................................................................................................201
13.5 Refactoring WordNodeTest..............................................................................................203
13.6 Further Tests of WordNode ...............................................................................................205
13.7 Implementing WordNode ..................................................................................................206
13.8 The WordSwitch Class .....................................................................................................208
13.9 The Implementation of lookForTarget ..........................................................................212
13.10 Finding the Path ..............................................................................................................215
13.11 Putting It All Together ......................................................................................................221
13.12 Summary and Step Details .............................................................................................222
13.12.1 D etails of Project Step 13.1 .................................................................................... 222
13.12.2 Details of Project Step 13.2 .................................................................................... 222
13.12.3 Details of Project Step 13.3 .................................................................................... 223
13.12.4 Details of Project Step 13.4 .................................................................................... 223
13.12.5 Details of Project Step 13.5 .................................................................................... 224
13.12.6 Details of Project Step 13.6 .................................................................................... 224
13.12.7 Details of Project Step 13.9 .................................................................................... 225
vi
Table of ConTenTs
13.12.8 Details of Project Step 13.10 .................................................................................. 225
13.12.9 Details of Project Step 13.12 .................................................................................. 226
13.12.10 Details of Project Step 13.13 ................................................................................ 226
13.12.11 Details of Project Step 13.16 ................................................................................ 227
13.12.12 Details of Project Step 13.21 ................................................................................ 227
Part III: Images �������������������������������������������������������������������������������������������229
Chapter 14: Color Pictures������������������������������������������������������������������������������������231
14.1 Modeling Color ..................................................................................................................231
14.2 Modeling Pictures .............................................................................................................232
14.3 Photographs ......................................................................................................................244
14.4 Flipping an Image .............................................................................................................248
14.5 S ummary and Solutions to Challenges .............................................................................253
Chapter 15: Pixel Transformations �����������������������������������������������������������������������259
15.1 Blood Sunset .....................................................................................................................259
15.2 A Unit Test .........................................................................................................................263
15.3 Conditional Transformations .............................................................................................264
15.4 Position-Based Transformations .......................................................................................270
15.5 S ummary and Solutions to Challenges .............................................................................274
Chapter 16: Cropping and Resizing Images����������������������������������������������������������281
16.1 Cropping ............................................................................................................................281
16.2 Improving the Unit Tests ...................................................................................................286
16.3 Shrinking an Image ...........................................................................................................287
16.4 Storing Images ..................................................................................................................294
16.5 S ummary and Solutions to Challenges .............................................................................296
Chapter 17: Project Dino ���������������������������������������������������������������������������������������301
17.1 Producing the Screen ........................................................................................................302
17.2 Photographing the Dinosaur .............................................................................................303
17.3 First Attempt at Superposition ..........................................................................................306
17.4 Letting the Background Through .......................................................................................309
vii
Table of ConTenTs
17.5 Hiding the Feet ..................................................................................................................313
17.6 Summary...........................................................................................................................316
Part IV: Vision ���������������������������������������������������������������������������������������������317
Chapter 18: Overview �������������������������������������������������������������������������������������������319
18.1 A Bit More Kotlin ...............................................................................................................319
18.2 Project Structure ...............................................................................................................321
18.3 Image Slicing ....................................................................................................................321
18.4 Summary and Step Details ...............................................................................................327
18.1.1 D etails of Project Step 18.1 ...................................................................................... 327
18.2.2 Details of Project Step 18.2 ...................................................................................... 328
18.3.3 Details of Project Step 18.3 ...................................................................................... 328
Chapter 19: Finding Digits ������������������������������������������������������������������������������������331
19.1 DigitFinder.........................................................................................................................331
19.2 Thresholding the Sign Images ...........................................................................................334
19.3 Slicing the Thresholded Image ..........................................................................................337
19.4 A More General Slicing Function .......................................................................................338
19.5 Filtering the Slices ............................................................................................................341
19.6 Summary and Step Details ...............................................................................................345
19.1.1 D etails of Project Step 19.1 ...................................................................................... 345
19.2.2 D etails of Project Step 19.2 ...................................................................................... 346
19.3.3 Details of Project Step 19.3 ...................................................................................... 347
Chapter 20: Parsing the Images ���������������������������������������������������������������������������349
20.1 Terminology .......................................................................................................................350
20.2 Project Structure ...............................................................................................................351
20.3 Identifying the Digit “1” ....................................................................................................351
20.4 Identifying the Digit “2” ....................................................................................................355
20.5 Identifying “5” and “7” ......................................................................................................356
20.6 Identifying “0” ...................................................................................................................357
viii
Table of ConTenTs
20.7 Summary and Step Details ...............................................................................................359
20.1.1 Details of Project Step 20.1 ...................................................................................... 359
20.2.2 Details of Project Step 20.2 ...................................................................................... 360
20.3.3 Details of Project Step 20.3 ...................................................................................... 360
20.4.4 Details of Project Step 20.4 ...................................................................................... 361
20.5.5 Details of Project Step 20.5 ...................................................................................... 362
20.6.6 Details of Project Step 20.6 ...................................................................................... 362
Chapter 21: Reading Speed Signs�������������������������������������������������������������������������365
21.1 SpeedReader .....................................................................................................................365
21.2 Base 10 Numbers ..............................................................................................................367
21.3 Putting It All Together ........................................................................................................369
21.4 Summary...........................................................................................................................369
21.5 Project Steps .....................................................................................................................370
21.5.1 D etails of Project Step 21.1 ...................................................................................... 370
21.5.2 D etails of Project Step 21.3 ...................................................................................... 371
21.5.3 D etails of Project Step 21.4 ...................................................................................... 371
Index ���������������������������������������������������������������������������������������������������������������������373
ix