2. Georgia Institute of Technology Introduction to Media Computation Barb Ericson Georgia Institute of Technology May 2006

3. Georgia Institute of Technology Media Computation: Teaching in a Relevant Context Presenting CS topics with media projects and examples –Iteration as creating negative and grayscale images –Indexing in a range as removing redeye –Algorithms for blending both images and sounds –Linked lists as song fragments woven to make music –Information encodings as sound visualizations

4. Georgia Institute of Technology Examples of Student Work Soup- Audio Collage Canon- LinkedList of (MIDI) Music

5. Georgia Institute of Technology Where is it being used? Introductory media computing in Python –Used for non-majors at Georgia Tech and ANU –Used for CS majors at U. Ill-Chicago, Kalamazoo College, Gainesville College. Introduction to data structures in Java –Used at Georgia Tech and Gainesville College Introduction to object-oriented programming in Java –Used at Dennison University, Duke, and U.Mass-Boston –Used in several high schools in Georgia

6. Georgia Institute of Technology Results Average CS1 success pre-MediaComp: Average 72.8% In MediaComp (51% female): Average 84% (as high as 90%) –Similar results at Gainesville, U.Ill-Chicago, ANU –Specific majors more dramatic: Management majors’s success rate 49% => 88% Students are excited, and becoming CS majors, CS minors, CS teachers, and Computational Media majors (over 100, 25% female)

7. Georgia Institute of Technology What works, Where it doesn’t What works –Open-ended assignments to allow for student creativity and expression Especially with their own media –Collaborative space for students to publicly share their media artifacts with others. –Transfer from Python =>Java Where it doesn’t –MediaComp isn’t “just the slow path” –Not allowing students to be creative

8. Georgia Institute of Technology Introduction to Java –Math operators, printing results, data types, casting, relational operators, Strings, variables Introduction to Programming –Creating and naming objects Using a turtle and a world –Creating new Turtle methods Draw simple shapes Using parameters Syllabus

9. Georgia Institute of Technology Syllabus - Continued Modifying Pictures using Loops –One-dimensional arrays –Use for-each, while, and for loops to –Increase/decrease colors, fake a sunset, lighten and darken, create a negative, and grayscale

10. Georgia Institute of Technology Syllabus - Continued Modifying Pixels in a Matrix –Two-dimensional arrays –Nested loops –Copying, mirroring, blending, rotation, scaling

11. Georgia Institute of Technology Syllabus - Continued Conditionally Modifying Pixels –Boolean expressions –Using && and || –Replacing a color, reducing red-eye, edge detection, sepia- toned, posterize, highlight extremes, blurring, background subtractions, chromakey

12. Georgia Institute of Technology Syllabus - Continued Drawing on Pictures –Using existing Java classes –Inheritance –Interfaces –Drawing simple shapes, drawing text, general copy, general scale, shearing, gradient paint, general blending, clipping

13. Georgia Institute of Technology Syllabus - Continued Modifying all Samples in a Sound –1D arrays –Loops –Conditional execution –Change volume, normalizing a sound (make it as loud as possible), force to extremes

14. Georgia Institute of Technology Syllabus - Continued Modifying Samples using Ranges –Loops –Clipping, splicing, reversing, mirroring

15. Georgia Institute of Technology Syllabus - Continued Combining and Creating Sounds –Class and private methods –Composing sounds, blending sounds, changing frequencies, and creating echoes – Creating sounds Sine Waves, Square Waves, Triangle Waves –MP3 and MIDI

16. Georgia Institute of Technology Syllabus - Continued Creating Classes –Identifying objects and classes –Defining a class –Overloading constructors –Creating and initializing an array –Creating getters and setters –Creating a main method –Javadoc comments Reusing a class via inheritance –ConfusedTurtle ConfusedTurtleTurtle

17. Georgia Institute of Technology Syllabus - Continued Creating and Modifying Text –String methods –Reading from and writing to files Handling Exceptions –Creating a form letter –Modifying programs –Getting text from networks –Creating random sentences –Using text to shift between media

18. Georgia Institute of Technology Syllabus - Continued Making Text for the Web –Throwing exceptions, “unnamed” package, HashMap, Generics, and Iterators –Generating HTML –Create a web page from a directory –Create a web page from other web pages –Databases –Creating a web page from a database

19. Georgia Institute of Technology Syllabus - Continued Encoding, Manipulating, and Creating Movies –Frame-based animations with simple shapes and text –Special effects – fade out, fake sunset, and chromakey

20. Georgia Institute of Technology Syllabus - Continued Speed –What makes programs fast? Compilers and Interpreters Writing a graphics interpreter and compiler Searching Algorithms that can’t be written –What makes computers fast? Clock rates, Storage, Display

21. Georgia Institute of Technology Syllabus - Continued Javascript –Syntax –User Interfaces –Multimedia

22. Georgia Institute of Technology Introduction to Java Introduction to DrJava Math Operators Integer and Floating Point Casting Primitive Types Relational Operators Order of Operations How to print to the console Representing Text (Strings) Invoking Class and Object Methods Using the Java API to find the methods for a class

23. Georgia Institute of Technology What is DrJava? DrJava is a free integrated development environment for doing Java programming –From Rice University –It is written in Java It has several window panes in it –For creating programs (definitions pane) –For trying out Java code (interactions pane) –Listing of open files (files pane)

24. Georgia Institute of Technology Math Operators Exercise Open DrJava and do the following in the interactions pane –Subtract 8 from 12 –Add 7 to 5 –Divide 5 by 2 –Divide 4.6 by 2 –Multiply 8 by 10 –Find the remainder when you divide 13 by 5

25. Georgia Institute of Technology Console Output Exercise Use System.out.println() to print the results of expression to the console –System.out.println(3 * 2); –System.out.println(14 – 5); –System.out.println(12 / 2); –System.out.println(256 + 234); –System.out.println("My" + "name"); –System.out.println("256 + 234"); Try using System.out.print() instead –What is the difference?

26. Georgia Institute of Technology Strings Java has a type called: String A string is an object that has a sequence of characters in Unicode –It can have no characters (the null string "") –It can have many characters "This is one long string with spaces in it. “ –Everything in a string will be printed out as it was entered Even math operations “128 + 234” Java knows how to add strings –It returns a new string with the characters of the second string after the characters of the first With no added space

27. Georgia Institute of Technology Methods Classes in Java define methods –Recipes or functions f(x) = x 2 –May take input –May produce an output Two Types –Object method Sent as a message to an object Implicitly passed the current object –Class method Sent as a message to a class Declared using the keyword static

28. Georgia Institute of Technology Method Exercise In DrJava’s interaction pane try these –Object methods "HELLO".toLowerCase() "This is a string".indexOf("is") " This is ".trim() –Class methods Math.abs(53) Math.abs(-3) Math.min(22,1) Character.getNumericValue('b')

29. Georgia Institute of Technology Message Always Have Parenthesis You can tell that out.println() is sending a message –Because of the () Messages always have () –Even if there are no parameters (arguments) If you are sending data along with a message it goes inside the parentheses –Separated by commas –Math.min(3,4);

30. Georgia Institute of Technology Java is Case Sensitive Some programming languages are case sensitive –Meaning that min isn’t the same as Min –Or string isn’t the same as String In Java primitive types are all lowercase –double, float, int, Class names start with an uppercase letter –So Math and System are the names of classes

31. Georgia Institute of Technology Java Naming Conventions In Java only Class names start with an uppercase letter –System, BufferedImage, Picture All other names start with lowercase letters but uppercase the first letter of each additional word –picture, fileName, thisIsALongName

32. Georgia Institute of Technology Teaching Java using Turtles How to add classes to your classpath in DrJava How to create objects in Java How to declare variables in Java How to invoke methods on objects in Java Objects control their data –And can refuse to do what you ask How to create a method in Java How to pass a parameter to a method in Java

33. Georgia Institute of Technology Creating a Simulation Computers let us simulate things –We do this by creating models of the things we want to simulate –We need to define what types of objects we will want in our simulation and what they can do Classes define the types and create objects of that type Objects act in the simulation Objects can have data and know how to do things

34. Georgia Institute of Technology Running a Simulation How many objects does it take to get a person fed at a restaurant? –Pick people to be the customer, greeter/seater, waiter, chef, and cashier and have them role play What data does each of these people need to do their job? What do they need to know how to do? What other objects do you talk about? How about simulating going to a dentist? –Or to the movies?

35. Georgia Institute of Technology Adding to the Classpath Click on Add Add bookClasses directory Click on Edit and then Preferences Click on Apply then OK

36. Georgia Institute of Technology Creating Objects in Java In Java to create an object of a class you use new Class(value, value, …); Our Turtle objects live in a World object –We must create a World object first –Try typing the following in the interactions pane: new World();

37. Georgia Institute of Technology Creating Objects If you just execute –new World(); You will create a new World object and it will display –But you will not have any way to refer to it again –Once you close the window the object can be garbage collected The memory can be reused We need a way to refer to the new object –to be able to work with it again

38. Georgia Institute of Technology Naming is Important If you get a new pet one of the first things you do is name it –Gives you a way to refer to the new pet without saying Please take that dog we got yesterday for a walk. Please take Fifi for a walk. In programming we name things we want to refer to again –Gives us a way to work with them –Like the World object This is called declaring a variable

39. Georgia Institute of Technology Declaring a Variable To be able to refer to an object again we need to specify what type of thing it is and give it a name –This is also called declaring a variable –Type name; OR –Type name = new Class(value, value, …); The equal sign doesn’t mean equal –But assign the value of the variable on the left to the result of the expression on the right –The following creates a variable named earth which refers to a World object created on the right World earth = new World();

40. Georgia Institute of Technology Declaring Variables Variables are names associated with values –If the type of the variable is null It doesn’t refer to an object yet –Variables can be reused World earth = null; earth = new World(); earth null earth World Object 1 earth World Object 2

41. Georgia Institute of Technology Limits on Declaring Variables You can't declare two variables with the same name! > World earth = new World(); Error: Redefinition of 'earth' You can change what an object variable refers to > World earth = new World(); > earth = new World();

42. Georgia Institute of Technology Turtle Basics The world starts off with a size of 640 by 480 –With no turtles World earth1 = new World(); The turtle starts off facing north and in the center of the world by default –You must pass a World object when you create the Turtle object Or you will get an error: java.lang.NoSuchMethodExcep tion: Turtle constructor Turtle tommy = new Turtle(earth1);

43. Georgia Institute of Technology Creating Several Objects You can create several World objects World mars = new World(); You can create several Turtle objects Turtle shar = new Turtle(mars); Turtle jen = new Turtle(mars); –One turtle is on top of the other

44. Georgia Institute of Technology What do Objects Look Like? Objects are created with space for their data Objects have a reference to the object that represents the class –Object of the class “Class” Name = Turtle Fields = pos, heading, color Methods = forward, backward, turnLeft, turn … Turtle : Class Pos = 320,240 Color = green Heading = 0 t1 : Turtletina : Turtle Pos = 110, 30 Color = blue Heading = 90

45. Georgia Institute of Technology Looking up Turtle Methods Open bookClasses/doc/Turtle.html and find the methods for the following: –How to turn a turtle left 90 degrees? –How to turn a turtle by a specific amount? –How many methods will make a turtle go forward How are they different? –What are the two ways to stop a turtle from being drawn? –How do you change the color of the pen? –What happens if you use setColor? –How would you draw a letter T with a Turtle?

46. Georgia Institute of Technology Objects can Refuse Turtles won’t move completely out of the boundaries of the world World world2 = new World(); Turtle turtle2 = new Turtle(world2); turtle2.forward(600);

47. Georgia Institute of Technology Objects send Messages Objects don’t “tell” each other what to do –They “ask” each other to do things Objects can refuse to do what they are asked –The object must protect it’s data Not let it get into an incorrect state A bank account object shouldn’t let you withdraw more money that you have in the account

48. Georgia Institute of Technology Creating a Method We can name a block of Java statements and then execute them again –By declaring a method in a class The syntax for declaring a method is –visibility returnType name(parameterList) –Visibility determines access Usually public or private The return type is the type of thing returned If nothing is returned use the keyword void –Name the method starting with a lowercase word and uppercasing the first letter of each additional word

49. Georgia Institute of Technology Example Method public void drawT() { this.forward(100); this.turnLeft(); this.penUp(); this.forward(40); this.turn(180); this.penDown(); this.forward(80); this.hide(); } The visibility is public The keyword void means this method doesn’t return a value The method name is drawT There are no parameters –Notice that the parentheses are still required The keyword this means the object this method was invoked on

50. Georgia Institute of Technology Adding a Method to a Class 1. Open file Turtle.java 2. Type the method before the last } // end 3. Compile open files

51. Georgia Institute of Technology Adding a Parameter to a Method The method drawT will always draw the same size T (height of 100 with a cross bar of 80 on top) But what if you want to draw different size Ts –By specifying the height –Use.8 x height for the length of the cross bar You can pass the height that you want as a parameter –And calculate the length of the cross bar

52. Georgia Institute of Technology Draw T with a Parameter public void drawT(int height) { int lengthCrossBar = (int) (height * 0.8); this.forward(height); this.turnLeft(); this.penUp(); this.forward(lengthCrossBar / 2); this.turn(180); this.penDown(); this.forward(lengthCrossBar); this.hide(); }

53. Georgia Institute of Technology Introduction to Media Computation What is media computation? How does color vision work? How can you make colors with red, green, and blue light? How do digital cameras and computer displays work? What is a pixel? How can you show a picture from a file in Java?

54. Georgia Institute of Technology What is Media Computation? Processing –picture elements –sound fragments –movie frames –Text files and HTML pages The speed and storage capacity of modern computers makes this possible –Even for beginning students just learning to program

55. Georgia Institute of Technology How Does Color Vision Work? Our eyes and brain work together to make sense of what we see The cones in our eyes are what allow us to see in color The rods allow us to see black, white, and shades of gray Our cones are sensitive to red, green, and blue light –All other colors are combinations of these

56. Georgia Institute of Technology Red, Green and Blue Light White light is a combination of red, green, and blue –Full intensity red, green, and blue combined Black is the absence of all light –No red, green or blue light All other colors are combinations –Of red, green, and blue –Of different intensities

57. Georgia Institute of Technology Color Exercise Start DrJava –In the interactions pane type ColorChooser.pickAColor(); –Click on the RGB tab and move the sliders to change the intensity of red, green, and blue –Make white, black, red, blue, green, yellow, violet, and orange

58. Georgia Institute of Technology Pictures are made up of Pixels Digital cameras record light at pixels Monitors display pictures using pixels Our limited vision acuity helps us to see the discrete pixels as a smooth picture –If we blow up the picture we can see the pixels

59. Georgia Institute of Technology Digital Pictures Capture the intensity of the red, green, and blue colors at each pixel Stored as a bunch of numbers –8 bits for red, 8 bits for green, 8 bits for blue –Need nearly 1 million bytes to store a 640 x 480 picture –Need 3 million bytes to store an image from a 1 megapixel (million pixel) camera Displayed as red, green, and blue colors on the computer display –Lots of them close together –Our brain sees a smooth color image

60. Georgia Institute of Technology Modifying Pictures using Loops Introduce one-dimensional arrays Change pixel colors one at a time by hand Change pixel colors in a loop –For-each –While –For Image Manipulations –Decrease/increase a color –Set a color to zero –Negate –Grayscale

61. Georgia Institute of Technology Pictures have lots of Pixels How can we refer to each pixel? –pixel1, pixel2, pixel3, pixel4, pixel5, … Do we really want to name each one? –There are 640 x 480 = 307,200 pixels How do we deal with lots of data of the same type? –Use an array

62. Georgia Institute of Technology What is an Array? Storage for a sequence of items –Of the same type You can access items by using an index The index starts at 0 –The first item is at index 0 –The last item is at index (length – 1) Arrays know their length (have a public length field) –arrayObj.length 379215 8326 012345 0123

63. Georgia Institute of Technology Negating an Image How would you turn a picture into a negative? –White should become black 255,255,255 becomes 0,0,0 –Black should become white 0,0,0 becomes 255,255,255 The new color is –255 – red, 255 – green, 255 - blue

64. Georgia Institute of Technology For-Each Loop Loops through all of the elements in an array Syntax for (type name : array) Example for (Pixel pixelObj : pixelArray) Each time through the loop this will be a different pixel from the array of pixels until all of the pixels in the array have been processed

65. Georgia Institute of Technology Negate Method /** * Method to negate the picture */ public void negate() { Pixel[] pixelArray = this.getPixels(); int redValue, blueValue, greenValue = 0; // loop through all the pixels for (Pixel pixelObj : pixelArray) { // get the values redValue = pixelObj.getRed(); greenValue = pixelObj.getGreen(); blueValue = pixelObj.getBlue(); // set the pixel's color pixelObj.setColor( new Color(255 - redValue, 255 - greenValue, 255 - blueValue)); }

66. Georgia Institute of Technology Testing Negate String file = "c:/intro-prog-java/mediasources/caterpillar.jpg"; Picture pictureObj = new Picture(file); pictureObj.explore(); pictureObj.negate(); pictureObj.explore();

67. Georgia Institute of Technology While Loop Executes the body of the loop while the condition is true Syntax while (condition) Example int index = 0; while (index < pixelArray.length) Often needs variables declared before the loop and incremented at the end of the body

68. Georgia Institute of Technology Exercise Modify the negate method to use a while loop –Add a variable for the current pixel –Add a variable for the current index –Remember to increment the index at the end of the body of the loop Create a new method that keeps only the blue value (sets the red and green values to 0) –Try it with a for-each loop –Try it with a while loop

69. Georgia Institute of Technology For Loop Has three areas: declaration, condition, and change Syntax for (declaration; condition; change) Example for (int i = 0; i < pixelArray.length; i++) Do the declaration before the body of the loop then each time through the loop check the condition and if true execute the body of the loop and then do the changes

70. Georgia Institute of Technology Exercise Modify the negate method to use a for loop –In the declaration area, declare the index –In the condition check that the index is less than the length of the array –In the increment area, increment the index Create a new method that reduces the blue value –Try it with a for-each loop –Try it with a while loop

71. Georgia Institute of Technology Modifying Pixels in a Matrix Introduce two-dimensional arrays Use Nested Loops Image Manipulations –Copying –Mirroring –Blending –Rotation –Scaling –Create a collage

72. Georgia Institute of Technology What is a two-dimensional array? The pixels in a picture are really stored in a two- dimensional array –Each pixel has a x value (horizontal location) –Each pixel has a y value (vertical location) –pictureObj.getPixel(x,y) returns the pixel at that location x y

73. Georgia Institute of Technology Example Two-Dimensional Arrays Maps –That street is in D-5 Battleship –Try I-5 Hit or miss Chairs at a theater or game –Row C seat 20

74. Georgia Institute of Technology Nested Loop How would you get all the pixels in a picture using their x and y values –From left to right and top to bottom? –x=0 and y=0, x=1 and y=0, x=2 and y=0, … –x=0 and y=1, x=1 and y=1, x=2 and y=1, … –x=0 and y=2, x=1 and y=2, x=2 and y=2, … We need to have one loop inside another –The outer loop counts y from 0 to height - 1 –The inner loop counts x from 0 to width - 1

75. Georgia Institute of Technology Alternative Nested Loop How would you get all the pixels in a picture using their x and y values –From top to bottom and left to right? –x=0 and y=0, x=0 and y=1, x=0 and y=2, … –x=1 and y=0, x=1 and y=1, x=1 and y=2, … –x=2 and y=0, x=2 and y=1, x=2 and y=2, … We need to have one loop inside another –The outer loop counts x to width - 1 –The inner loop counts y from 0 to height - 1

76. Georgia Institute of Technology Nested Loop Template // loop through the rows for (int y = 0; y < this.getHeight(); y++) { // loop through the columns for (int x = 0; x < this.getWidth(); x++) { // get the current pixel pixelObj = this.getPixel(x,y); // do something to the color // set the new color pixelObj.setColor(colorObj); }

77. Georgia Institute of Technology Vertical Mirroring What if we want to pretend to place a mirror in the middle of the picture –We would see the left side of the picture mirrored on the right side

78. Georgia Institute of Technology Thinking Through Vertical Mirroring If we just think of a number at each x and y location instead of a color –The mirroring would look like this: Can you find the algorithm to do this? 12345 54321 12345 12321 54345 12321 01234 0 1 2

79. Georgia Institute of Technology What is the Vertical Mirror for this? Try the solve the problem for small samples If you can’t solve it on a small sample –You can’t write a program to solve it 123 456 789 012 0 1 2 012 0 1 2

80. Georgia Institute of Technology Mirror Vertical Algorithm Loop through all the rows (y starts at 0, increments by 1, and is less than the picture height) –Loop with x starting at 0 and x less than the midpoint (mirror point) value Get the left pixel at x and y Get the right pixel at width – 1 - x Set the color for the right pixel to be the color of the left pixel 12345 54321 12345 12321 54345 12321

81. Georgia Institute of Technology Mirror Vertical Algorithm to Code We are going to need the midpoint int midpoint = this.getWidth() / 2; Loop through the rows (y values) for (int y = 0; y < this.getHeight(); y++) { –Loop through x values (starting at 1) for (int x = 0; x < midpoint; x++) { Set right pixel color to left pixel color Pixel leftPixel = this.getPixel(x, y); Pixel rightPixel = this.getPixel(this.getWidth() - 1 - x, y); rightPixel.setColor(leftPixel.getColor());

82. Georgia Institute of Technology Mirror Vertical Method public void mirrorVertical() { int mirrorPoint = this.getWidth() / 2; Pixel leftPixel = null; Pixel rightPixel = null; // loop through the rows for (int y = 0; y < this.getHeight(); y++) { // loop from 0 to just before the mirror point for (int x = 0; x < mirrorPoint; x++) {

83. Georgia Institute of Technology Mirror Vertical Method - Continued leftPixel = this.getPixel(x, y); rightPixel = this.getPixel(this.getWidth() – 1 – x, y); rightPixel.setColor(leftPixel.getColor()); }

84. Georgia Institute of Technology Trying Mirror Vertical Create the picture –Picture p1 = new Picture( FileChooser.getMediaPath("caterpillar.jpg"); Invoke the method on the picture –p1.mirrorVertical(); Show the picture –p1.show();

85. Georgia Institute of Technology Mirror Horizontal What about mirroring around a mirror held horizontally in the vertical center of the picture? –Like a reflection in a lake?

86. Georgia Institute of Technology Thinking Through Mirror Horizontal Again think of a number at each x and y location –Instead of a color –And try it with a small sample How can we write a nested for loop to do this? 123 456 789 123 456 123 012 0 1 2 012 0 1 2

87. Georgia Institute of Technology Horizontal Mirroring? Try to solve the problem for several small samples problems See if you can come up with the algorithm to solve it –Test it more small samples 12345 54321 89123 01234 0 1 2

88. Georgia Institute of Technology Mirror Horizontal Algorithm Get the vertical midpoint –Picture height / 2 Loop through all the x values –Loop from y=0 to y < vertical midpoint Get the top pixel –At x and y Get the bottom pixel –Height - 1 - y Set the bottom pixel’s color to the top pixel color 123 456 789 123 456 123

89. Georgia Institute of Technology Mirror Horizontal Exercise Write the method to mirror the top half of the picture to the bottom half. –This is a motorcycle redMotorcycle.jpg How about mirroring bottom to top?

90. Georgia Institute of Technology Conditionally Modifying Pixels Boolean expressions Using && and || to combine boolean expressions Image Manipulations –Replacing a color –Reducing red-eye –Edge detection –Sepia-toned –Posterize –Highlight extremes –Blurring –Background subtraction and Chromakey

91. Georgia Institute of Technology Remove Red Eye Red eye is when the flash from the camera is reflected from the subject’s eyes We want to change the red color in the eyes to another color –But not change the red of her dress

92. Georgia Institute of Technology Red Eye Algorithm We can find the area around the eyes to limit where we change the colors –Using pictureObj.explore() –But we still just want to change the pixels that are “close to” red. –We can find the distance between the current color and our definition of red And change the color of the current pixel only if the current color is within some distance to the desired color

93. Georgia Institute of Technology Conditional Execution Sometimes we want a statement or block of statements executed only if some expression is true –We can use the “if” statement in Java if (colorDistance < value) Statement or block to execute next statement statement if (expression) true false Statement or block

94. Georgia Institute of Technology Color Distance The distance between two points is computed as –Square root of (( x1 – x2) 2 + (y1 – y2) 2 ) The distance between two colors can be computed –Square root of ((red1 – red2) 2 + (green1-green2) 2 + (blue1 – blue2) 2 ) –There is a method in the Pixel class to do this double dist = pixelObj.colorDistance(color1);

95. Georgia Institute of Technology Remove Red Eye Method public void removeRedEye(int startX, int startY, int endX, int endY, Color newColor) { Pixel pixelObj = null; // loop through the pixels in the rectangle defined by the // startX, startY, and endX and endY for (int x = startX; x < endX; x++) { for (int y = startY; y < endY; y++) { // get the current pixel pixelObj = getPixel(x,y);

96. Georgia Institute of Technology Remove Red Eye Method // if the color is near red then change it if (pixelObj.colorDistance(Color.red) < 167) { pixelObj.setColor(newColor); }

97. Georgia Institute of Technology Testing removeRedEye String file = FileChooser.getMediaPath("jenny-red.jpg"); Picture p = new Picture(file); p.explore(); p.removeRedEye(110,91,192,103, java.awt.Color.BLACK); p.explore();

98. Georgia Institute of Technology Exploring Remove Red Eye Type in x and y

99. Georgia Institute of Technology Chroma Key – Blue Screen For TV and movie special effects they use a blue or green screen –Here just a blue sheet was used –Professionally you need an evenly lit, bright, pure blue background With nothing blue in the scene

100. Georgia Institute of Technology Chromakey Write the method chromakey that takes a new background picture as an input parameter –It will loop through all the pixels –If the pixel color is blue (red + green < blue) –Replace the pixel color with the color from the new background pixel (at the same location)

101. Georgia Institute of Technology Conditional Operators We can check if several things are true - And –Using && (evaluation stops if the first item is false) –Using & (to always evaluate both operands) We can check if at least one of several things are true - Or –Using || (evaluation stops if the first item is true) –Using | (to always evaluate both operands) We can check if only one and only one of the things is true – Exclusive Or –Using ^

102. Georgia Institute of Technology Sepia-Toned Pictures Have a yellowish tint, used to make things look old and western

103. Georgia Institute of Technology Sepia-toned Algorithm First make the picture grayscale. Loop through the pixels in the picture –Change the shadows (darkest grays) to be even darker (0 <= red < 60) –Make the middle grays a brown color (60 <= red < 190) –Make the highlights (lightest grays) a bit yellow (190 <= red) Increase red and green Or decrease blue

104. Georgia Institute of Technology Using Multiple If Statements If we are doing different things based on a set of ranges –0 <= x <= 5 –5 < x <= 10 –10 < x if (0 <= x && x <= 5) Statement or block if (5 < x && x <= 10) Statement or block if (10 < x) Statement or block

105. Georgia Institute of Technology Using “else if” for > 2 Options If we are doing different things based on a set of ranges –0 <= x <= 5 –5 < x <= 10 –10 < x You don’t need to check if x > 5 since the first if block would have executed if it was if (0 <= x && x <= 5) Statement or block else if (x <= 10) Statement or block else Statement or block

106. Georgia Institute of Technology Conditionals with > 2 Choices if (0 <= x && x <= 5) { } else if (x <= 10) { } else // what is x? { }

107. Georgia Institute of Technology Sepia-toned Method public void sepiaTint() { Pixel pixelObj = null; double redValue = 0; double greenValue = 0; double blueValue = 0; // first change the current picture to grayscale this.grayscale();

108. Georgia Institute of Technology Sepia-toned Method - Cont // loop through the pixels for (int x = 0; x < this.getWidth(); x++) { for (int y = 0; y < this.getHeight(); y++) { // get the current pixel and color values pixelObj = this.getPixel(x,y); redValue = pixelObj.getRed(); greenValue = pixelObj.getGreen(); blueValue = pixelObj.getBlue();

109. Georgia Institute of Technology Sepia-toned Method - Cont // tint the shadows darker if (redValue < 60) { redValue = redValue * 0.9; greenValue = greenValue * 0.9; blueValue = blueValue * 0.9; } // tint the midtones a light brown by reducing the blue else if (redValue < 190) { blueValue = blueValue * 0.8; }

110. Georgia Institute of Technology Sepia-toned Method - Cont // tint the highlights a light yellow // by reducing the blue else { blueValue = blueValue * 0.9; } // set the colors pixelObj.setRed((int) redValue); pixelObj.setGreen((int) greenValue); pixelObj.setBlue((int) blueValue); }

111. Georgia Institute of Technology Testing sepiaTint String file = FileChooser.getMediaPath(“gorge.jpg”); Picture p = new Picture(file); p.explore(); p.sepiaTint(); p.explore();

112. Georgia Institute of Technology Summary You can use DrJava's interactions pane –To try out Java code You can use Turtle and World –To create objects and invoke methods –To declare variables –To write a method You can use pictures to teach –One-dimensional and two-dimensional arrays –Looping (for-each, while, for) –Conditionals