IAT 800

Lecture 8PImage and PFont

Oct 13, Fall 2009 IAT 800 2

Outline

Programming concepts– PImage– PFont

Oct 13, Fall 2009 IAT 800 3

Loading Images

Loading Images– Give your project a name and save.– Place the image file in:

• <processing dir>/sketchbook/<project name>/data/

– Use this code:PImage im = loadImage(“<image filename>”);

Oct 13, Fall 2009 IAT 800 4

Displaying Images

image() shows your image.– image(im, 0, 0) will display your image

from the last slide at the top left of the window.

Oct 13, Fall 2009 IAT 800 5

Accessing Pixels

The PImage class allows you to access the RGB values of each individual pixel of the image, with the pixels[] array.

You can get the width and height of the image file using the width and height fields of PImage.

Oct 13, Fall 2009 IAT 800 6

Accessing Pixels

How do we know which pixel to look for in the array?

0 1 32 4

0

1

2

3

Oct 13, Fall 2009 IAT 800 7

Accessing Pixels

How do we know which pixel to look for in the array?

0 1 2 3 4

0 1 32 4

0

1

2

3

0

Oct 13, Fall 2009 IAT 800 8

Accessing Pixels

How do we know which pixel to look for in the array?

0 1 2 3 4 5 6 7 8 9

0 1 32 4

0

1

2

3

0 1

Oct 13, Fall 2009 IAT 800 9

Accessing Pixels

How do we know which pixel to look for in the array?

0 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

0 1 32 4

0

1

2

3

0 1 2 3

Oct 13, Fall 2009 IAT 800 10

Accessing Pixels

Array Index– x + y*width

0 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

0 1 32 4

0

1

2

3

0 1 2 3

(4, 0) = 4 + 0*5 = 4(3, 2) = 3 + 2*5 = 13

Oct 13, Fall 2009 IAT 800 11

Accessing Pixels

What would a piece of code look like that got a color from a pixel?

Let’s look at some applications of this.

PImage im = loadImage(“test1.jpg”);color c1 = im.pixels[3 + 2*im.width]; // gets color at (3, 2)stroke(c1); // set our line color so we can draw with this color.

Oct 13, Fall 2009 IAT 800 12

Window vs. Image

The drawing window also has a pixels[] array. – You must call loadPixels(); to get the

image from the screen – You don’t need a PImage object.

loadPixels();color c2 = pixels[3 + 2*width]; // gives us the color at (3, 2) in the window.

Oct 13, Fall 2009 IAT 800 13

Window vs. Image

When would we want to use both of these?– Use the Window’s pixels if you want to

draw more things based on the image that’s already on the screen.

– Use the Image’s pixels if you want to manipulate the pixels of the image before you draw them.

Oct 13, Fall 2009 IAT 800 14

2D Arrays

Java lets us make Arrays of Arrays, otherwise called 2D Arrays. These are very useful for accessing arrays of pixels like the ones we’ve been working with.

int[][] bob = new int[3][4];color[][] pixels2d = new color[200][200];

Oct 13, Fall 2009 IAT 800 15

2D Arrays

Processing doesn’t provide us with a 2D array of pixels to use, so let’s develop a class that will make manipulating pixels easier.

Oct 13, Fall 2009 IAT 800 16

2D Arrays

Interestingly, 2D Arrays are just covering up a 1D array much like the pixels[] array. color[][] pixels2d = new color[20][20];color c2 = pixels2d[3][2];

color[] pixels1d = new color[400];color c1 = pixels1d[3 + 2*20];

Underneath, these two pieces of code do the same thing. The 2D arrayconvention just makes it easier for us to access the array based on thingslike our x and y values.

Oct 13, Fall 2009 IAT 800 17

PFont

PFont is the Processing class for manipulating fonts– Like PImage for images

Use PFont with – PFont loadFont() – loads a font– textFont(PFont font, int size) – sets the current font– text(String str, int x, int y) – draws a string in the

current font at the current location• Also text(String str, float x, float y)

Oct 13, Fall 2009 IAT 800 18

Simple example

// the fonts must be located in the data directory

PFont eureka = loadFont("Eureka90.vlw");PFont zig = loadFont("Ziggurat-HTF-Black-

32.vlw");textFont(eureka, 44); text("word", 10, 30);textFont(zig, 44);text("word", 10, 60);

Oct 13, Fall 2009 IAT 800 19

Use fill() to change the color of text

// the fonts must be located in the data directoryPFont eureka = loadFont("Eureka90.vlw");PFont zig = loadFont("Ziggurat-HTF-Black-32.vlw");fill( 0, 255, 0 );textFont( eureka, 44); text( "word", 10, 30);textFont( zig, 44);fill( 255, 0, 0);text( "word", 10, 60);

Oct 13, Fall 2009 IAT 800 20

textMode sets the alignment textAlign( LEFT );

– x, y is the upper left hand corner of the text

textAlign( RIGHT );– x, y is the upper right hand corner of the

text

textAlign( CENTER );– x, y is the upper center of the text

Oct 13, Fall 2009 IAT 800 21

Producing text effects All the transform methods apply to drawing text

– That means you can translate, rotate, and scale text

Combined with draw(), this means you can move text around the screen in real time– Remember, the movement of the rocket and

asteroids in our asteroids example was just translation and rotation

So you can make textual machines where text moves around the screen!

Oct 13, Fall 2009 IAT 800 22

Processing examplePImage im ;PFont eur ;PFont zig ;

void setup(){ size( 600, 600 ); im = loadImage( "cdshaw.96.jpg" ); for( int i = 600 ; i >= 0 ; i -= 50 ) image( im, i, i ); eur = loadFont( "Eureka90.vlw" ); zig = loadFont( "Ziggurat-HTF-Black-

32.vlw" ); textFont( eur );

}

void draw( ){ image( im, mouseX-370, mouseY-210 ); color c1 = im.pixels[365 + 210 * im.width ] ; loadPixels(); c1 = pixels[ 3 + 2 * width ] ; stroke( c1 ); fill( c1 ); textAlign( LEFT ); ellipse( mouseX, mouseY, 20, 10 ); textFont( eur, 44 ); text( "Yo!", mouseX + 20, mouseY + 20 ); fill( 255, 0, 0); pushMatrix(); textAlign( RIGHT ); rotate( 0.2); textFont( zig, 44 ); text( "Yo?", mouseX, mouseY + 100 ); popMatrix();}