Learning Processing: A Beginner's Guide to Programming Images ...

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It is fairly intuitive for us to think angles in terms of degrees. For example, the rectangle in Figure 13.6 is rotated 45 ° around its center. Processing , however, requires angles to be specifi ed in radians . A radian is a unit of measurement for angles defi ned by the ratio of the length of the arc of a circle to the radius of that circle. One radian is the angle at which that ratio equals one (see Figure 13.7 ). An angle of 180° � PI radians. An angle of 360 ° � 2*PI radians, and 90 ° � PI/2 radians, and so on. fi g. 13.7 angle � 1 radian radius Th e formula to convert from degrees to radians is: Radians � 2 * PI * (degrees/360) PI, What Is It? arc length � radius fi g. 13.6 Mathematics 211 Fortunately for us, if we prefer to think in degrees but code with radians, Processing makes this easy. Th e radians( ) function will automatically convert values from degrees to radians. In addition, the constants PI and TWO_PI are available for convenient access to these commonly used numbers (equivalent to 180 ° and 360 ° , respectively). Th e following code, for example, will rotate shapes by 60 ° (rotation will be fully explored in the next chapter). float angle = radians(60); rotate(angle); Th e mathematical constant PI (or π ) is a real number defi ned as the ratio of a circle’s circumference (the distance around the perimeter) to its diameter (a straight line that passes through the circle center). It is equal to approximately 3.14159.
212 Learning Processing 13.8 Exercise 13-4: A dancer spins around two full rotations. How many degrees did the dancer rotate? How many radians? Trigonometry Degrees: _____________________ Radians: _____________________ Sohcahtoa. Strangely enough, this seemingly nonsense word, sohcahtoa , is the foundation for a lot of computer graphics work. Any time you need to calculate an angle, determine the distance between points, deal with circles, arcs, lines, and so on, you will fi nd that a basic understanding of trigonometry is essential. Trigonometry is the study of the relationships between the sides and angles of triangles and sohcahtoa is a mnemonic device for remembering the defi nitions of the trigonometric functions, sine, cosine, and tangent. See Figure 13.8 . • soh : sine � opposite/hypotenuse • cah : cosine � adjacent/hypotenuse • toa : tangent � opposite/adjacent hypotenuse angle adjacent fi g. 13.8 opposite right angle � 90° � π/2 radians Any time we display a shape in Processing , we have to specify a pixel location, given as x and y coordinates. Th ese coordinates are known as Cartesian coordinates, named for the French mathematician René Descartes who developed the ideas behind Cartesian space. Another useful coordinate system, known as polar coordinates , describes a point in space as an angle of rotation around the origin and a radius from the origin. We can’t use polar coordinates as arguments to a function in Processing . However, the trigonometric formulas allow us to convert those coordinates to Cartesian, which can then be used to draw a shape. See Figure 13.9 .
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Learning Processing A Beginner’s
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Learning Processing A Beginner’s
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Contents Acknowledgments vii Introd
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Acknowledgments In the fall of 2001
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Introduction What is this book? Th
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Introduction xi While both of these
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Introduction xiii Th e book is desi
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Introduction xv Th is book’s web
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Introductory Exercise: Write instru
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Lesson One The Beginning 1 Pixels 2
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1 Pixels “ A journey of a thousan
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1.2 Simple Shapes Pixels 5 Th e vas
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0 1 2 3 4 5 6 7 8 9 fi g. 1.9 top l
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1.3 Pixels 9 Exercise 1-3: Reverse
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Example 1-2: noFill ( ) background(
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fi g. 1.19 Pixels 13 Exercise 1-5:
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colorMode(RGB,100); Pixels 15 Th e
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2 2.1 Processing “ Computers in t
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fi g. 2.2 Once you have opened the
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Let’s write a fi rst example ( se
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Line 9 fi g. 2.6 Processing is case
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fi g. 2.7 Processing 25 Processing
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Example 2-1: Zoog again size(200,20
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Processing 29 To see the applet wor
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3 3.1 Interaction “ Always rememb
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Let’s look at what will surely be
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3.3 Variation with the Mouse Intera
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Draw Zoog's eyes fill(0); ellipse(8
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3.4 Mouse Clicks and Key Presses In
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Draw Zoog's eyes fill(mo useX,0,mou
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Lesson Two Everything You Need to K
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4 4.1 Variables “ All of the book
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4.2 Variable Declaration and Initia
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A variable can also be initialized
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x = 5; x = a + b; x = y - 10 * 20;
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void draw() { // Draw the backgroun
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4.6 Random: Variety is the spice of
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4.7 Example 4-7: Filling variables
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5 5.1 Conditionals Conditionals 59
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Finally, for testing multiple condi
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Conditionals 63 It is worth pointin
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Conditionals 65 Getting into the ha
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Our fi rst instinct might be to wri
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5.5 Multiple Rollovers Conditionals
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Conditionals 71 We can then check t
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5.7 Conditionals 73 Exercise 5-8: E
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Reversing the Polarity of a Number
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One way to solve this problem is to
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Display the square fill(0); noStrok
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6 Loops “ Repetition is the reali
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Loops 83 (see Chapter 5). However,
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while (y < 100) { // Loop! } 3. Wha
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while (x < = endLegs) { line(x,y,x,
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Th e same exact loop can be program
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Loops 91 Th is was a nice simplifi
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6.6 Loop Inside the Main Loop Loops
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6.7 float distance = abs(mouseX - i
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Draw Zoog's legs stroke(0); line(x-
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Lesson Three Organization 7 Functio
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7 7.1 Functions “ When it’s all
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7.2 “ User Defi ned ” Functions
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Example 5-6: Bouncing ball // Decla
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7.5 Functions 107 Exercise 7-3: Tak
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Functions 109 It should be fairly a
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int globalX = 0; int globalY = 100;
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void setup() { println( "a"); funct
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If we did not include a return stat
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7.8 Zoog Reorganization Zoog is now
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void draw() { } background(0); // D
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8 8.1 Objects “ No object is so b
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Setup: Draw: Initialize car color.
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Objects 125 • The Class Name—Th
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Objects 127 One other thing; with t
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fi g. 8.1 fi g. 8.2 fi g. 8.4 fi g.
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Objects 131 Nevertheless, this is q
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void draw() { } background(100); ba
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Objects 135 modular, reusable packa
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Lesson Three Project Step 1. Take y
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Lesson Four More of the Same 9 Arra
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9 Arrays “ I might repeat to myse
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Car myCar80 Car myCar81 Car myCar82
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9.3 Declaring and Creating an Array
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9.4 Initializing an Array One way t
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Example 9-5: Using a for loop to in
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Arrays 151 Now comes the hard part.
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9.7 Arrays 153 Exercise 9-7: Rewrit
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9.8 Interactive Objects Arrays 155
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Check if point is inside of Stripe
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alls[i].gravity(); balls[i].move();
Page 180 and 181: Draw Zoog's arms with a for loop fo
Page 182 and 183: Lesson Five Putting It All Together
Page 184 and 185: 10 10.1 Algorithms “ Lather. Rins
Page 186 and 187: Translating the preceding algorithm
Page 188 and 189: void draw() { background(255); stro
Page 190 and 191: Example 10-2: Bouncing ball class c
Page 192 and 193: Now that the function is complete,
Page 194 and 195: 10.6 // Constructor Ball(float temp
Page 196 and 197: Algorithms 177 With the above logic
Page 198 and 199: Drop() { r = 8; // All raindrops ar
Page 200 and 201: Example 10-7: Drops one at a time /
Page 202 and 203: Algorithms 183 Notice how every sin
Page 204 and 205: oolean intersecting = ball1.interse
Page 206 and 207: } void setLocation(float tempX, flo
Page 208 and 209: Algorithms 189 It is important to r
Page 210 and 211: 11 Debugging “ Th e diff erence b
Page 212 and 213: Debugging 193 Once all the code is
Page 214 and 215: 12 Libraries “ If truth is beauty
Page 216 and 217: or /Applications/Processing 0135/ c
Page 218 and 219: Lesson Six The World Revolves Aroun
Page 220 and 221: 13 Mathematics Mathematics 201 “
Page 222 and 223: Mathematics 203 Th erefore, modulo
Page 224 and 225: Th e probability of a coin fl ippin
Page 226 and 227: 13.6 Perlin Noise Mathematics 207 O
Page 228 and 229: Mathematics 209 How quickly we incr
Page 232 and 233: fi g. 13.9 y-axis sine(theta) � y
Page 234 and 235: Example 13-6: Oscillation float the
Page 236 and 237: Mathematics 217 In 1975, Benoit Man
Page 238 and 239: Mathematics 219 said about recursio
Page 240 and 241: Mathematics 221 A two-dimensional a
Page 242 and 243: Example 13-10: Two-dimensional arra
Page 244 and 245: } void display() { } // FILL IN Mat
Page 246 and 247: 14 14.1 Translation and Rotation (i
Page 248 and 249: Our fi rst instinct might be to add
Page 250 and 251: Example 14-3: A rectangle moving al
Page 252 and 253: When using the OPENGL mode, you mus
Page 254 and 255: Translation and Rotation (in 3D!) 2
Page 256 and 257: 14.5 fill(150,150); vertex(-t, t,-t
Page 258 and 259: 14.6 Example 14-5: Rectangle rotati
Page 266 and 267: fill(0,100); // Note the use of pus
Page 268 and 269: 14.9 Example 14-17: Nested push and
Page 270 and 271: stroke(0); fill(175); ellipse(0,0,d
Page 272 and 273: Lesson Seven Pixels Under a Microsc
Page 274 and 275: 15 Images Images 255 “ Politics w
Page 276 and 277: And yet: PImage img = loadImage( "f
Page 278 and 279: 15.3 My Very First Image Processing
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Images 261 Even better, if we just
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Images 263 // Create a grayscale co
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Images 265 15.6 Intro to Image Proc
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Images 267 Since we are altering th
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15.9 More on fi lter( ): fi lter(mo
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Images 271 Example 15-13 performs a
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Example 15-14: “ Pointillism ”
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16 16.1 Video “ I have no memory.
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Video 277 Th e above line of code i
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void draw() { // Check to see if a
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16.3 Recorded Video Video 281 Displ
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16.4 Video 283 Exercise 16-3: Using
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Video 285 For every square at colum
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} } // Each rect is colored white w
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16.5 Video as Sensor, Computer Visi
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Now, we are ready to compare the co
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16.6 Video 293 Exercise 16-5: Take
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void setup() { size(320,240); video
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Example 16-13: Simple motion detect
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16.8 // Step 4, compare colors (pre
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Lesson Seven Project Develop a soft
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Lesson Eight The Outside World 17 T
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17 17.1 Text “ I could entertain
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Exercise 17-2: Loop through and pri
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17.3 Displaying Text Text 309 We wi
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println(PFont.list()); For demonstr
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X = �50 fi g. 17.4 float w = text
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Example 17-4: Text mirror import pr
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textFont(f); // Set the font transl
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Exercise 17-9: Using textWidth( ) ,
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Example 17-7: Boxes along a curve P
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Text 323 Exercise 17-10: Create a s
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18 Data Input “ A million monkeys
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Example 18-1: User input PFont f; /
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Data Input 329 Th e reverse of spli
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Example 18-2: Graphing comma separa
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Data Input 333 Th e rollover( ) fun
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18.4 diameter = diameter_; } // Tru
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} // Find the index of the end tag
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void mousePressed() { // Increment
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18.6 for (int i = 0; i < kinglear.l
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Create and make an asynchronous req
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� student � � id � 002 �
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Requests for XML data are made via
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18.8 Using the Processing XML Libra
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XMLElement diameterElement = childr
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Example 18-10: A Yahoo search impor
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However, if you request a URL on a
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19 19.1 Data Streams “ I’m mad
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import processing.net.* ; Server se
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Data Streams 361 Once the server is
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19.4 void draw() { background(255);
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Data Streams 365 must be networked
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Data Streams 367 will send X , Y co
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Data Streams 369 Here is the full S
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Here is the entire client sketch: 1
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Data Streams 373 Serial communicati
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Data Streams 375 of information, ca
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Corresponding Arduino code: int sen
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Lesson Nine Making Noise 20 Sound 2
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20 Sound “ Check. Check. Check 1.
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void setup() { Sonia.start(this); }
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void mousePressed() { // If the use
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Sound 387 check and see if a sound
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Is a point inside the doorbell (use
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Pressing the mouse stops and starts
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20.6 void draw() { background(255,1
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In code, this translates to: // If
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21 Exporting “ Wait a minute. I t
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Th is code can be inserted anywhere
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void setup() { size(400, 400); begi
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Exporting 403 save( ) takes one arg
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Exporting 405 Example 21-5 records
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Lesson Ten Beyond Processing 22 Adv
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22 Advanced Object-Oriented Program
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class Point { float x,y; Point(floa
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Advanced Object-Oriented Programmin
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Advanced Object-Oriented Programmin
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class Circle extends Shape { // inh
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for (int i = 0; i < dogs.length; i
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22.5 Example 22-2: Polymorphism //
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23 23.1 Java “ I l o ve c off ee,
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Java 425 instead of Processing , sp
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fi g. 23.2 Java 427 Just as with th
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Particle p = parray[i]; p.run(); p.
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Hint: Add a function that returns a
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Example 23-4: Super fancy ArrayList
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Java 435 It is sad when these error
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Th e tutorials will cover the same
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Appendix: Common Errors Appendix 43
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Error: No accessible fi eld named
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void draw() { thing.display(); } Co
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Error: Perhaps you wanted the overl
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Index AIFF (Audio Interchange File
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Fill( ) function 10 , 11 , 256 , 30
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One-dimensional Perlin noise 208 OP
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solar system, processing 247-9 vert
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