How to use the Java class libraries

How to use the Java class libraries Brief documentation of how to do this all with Java.

Java materials • We’re developing Java versions of our Media Computation materials for the teachers workshops that we’re developing. • Original classes by Guzdial for Jython, revised by students, and now made readable by Barb Ericson

Using DrJava

Basic picture opening & showing > String fileName = FileChooser.pickAFile(); > System.out.println(fileName); C:\intro-prog-java\mediasources\catapillarClipart.jpg > Picture picture=new Picture(fileName); > picture.show(); > System.out.println(picture); Picture, filename C:\intro-prog-java\mediasources\catapillarClipart.jpg height 181 width 360

Methods of Pictures • show() • repaint() • explore() – opens a Picture explorer • Pixel [] getPixels() • Pixel getPixel(x,y) • int getWidth() • int getHeight() • writePictureTo(filename)

Methods of Pixels • int getGreen(), getRed(), getBlue() • setGreen(value), setRed(value), setBlue(value) • Color getColor() • setColor(color) • int getX(), getY()

Methods of Color • new Color(red, green, blue) • ColorChooser.pickAColor() • SimplePicture.getColorDistance(color1,color2) • color.darker(), color.brighter()

/** * Method to decrease the red by half in the current picture */ public void decreaseRed() { Pixel[] pixels = this.getPixels(); Pixel p = null; int value = 0; // loop through all the pixels for (int i = 0; i < pixels.length; i++) { // get the current pixel p = pixels[i]; // get the value value = p.getRed(); // set the red value to half what it was p.setRed((int) (value * 0.5)); } } decreaseRed in Java

/** * Method to copy Katie rotated to the left 90 degrees * @return the picture after Katie has been copied and rotated to the left 90 */ public static Picture copyKatieSideways() { String sourceFile = Picture.getMediaPath("KatieFancy.jpg"); Picture sourcePicture = new Picture(sourceFile); String targetFile = Picture.getMediaPath("7inx95in.jpg"); Picture targetPicture = new Picture(targetFile); Pixel sourcePixel = null; Pixel targetPixel = null; // loop through the columns for (int sourceX = 0, targetX=0; sourceX < sourcePicture.getWidth(); sourceX++, targetX++) { // loop through the rows for (int sourceY = 0, targetY =0; sourceY < sourcePicture.getHeight(); sourceY++, targetY++) { // set the target pixel color to the source pixel color sourcePixel = sourcePicture.getPixel(sourceX,sourceY); targetPixel = targetPicture.getPixel(targetY,targetX); targetPixel.setColor(sourcePixel.getColor()); } } // show the source and target pictures sourcePicture.show(); targetPicture.show(); return targetPicture; }

Basic sound opening & playing > Sound mySound = new Sound(FileChooser.pickAFile()); > mySound.play() > mySound Sound file: thisisatest.wav length: 129026 > int asample = mySound.getSample(1); > asample 6852 > mySound.setSample(1,-17); > mySound.getSample(1) -17

Sound methods aren’t as clean yet • They’re still in the form we’ve used them in Jython, not as Barb has been making them for Java.

/** Method to decrease volume by 50% * */ public void decreaseVolume() { int mySample = 0; for (int index = 0; index < getLengthInFrames()-1; // getLengthInFrames currently one too long index++) { try { mySample = getSample(index); // getSample 0-based mySample *= 0.5; setSample(index, (int) mySample); } catch (SoundException ex) { System.out.println("SoundException occured"); } } } decreaseVolume

Example using decreaseVolume > Sound mySound = new Sound(FileChooser.pickAFile()); > mySound Sound file: thisisatest.wav length: 129026 > mySound.getSample(1) 6852 > mySound.getLengthInFrames() 64513 > mySound.decreaseVolume(); > mySound.play() > mySound.getSample(1) 3426

How to use the Java class libraries