Advanced User Interfaces with Java SD’98 - Session 3206 Ted Faison [email protected] Faison Computing Inc. .

Advanced User Interfaces with Java

SD’98 - Session 3206

Ted Faison

[email protected]

Faison Computing Inc.

www.faisoncomputing.com

JDK 1.2 - A Better Graphics Framework

JDK 1.1 had little or no support for complex shapes, coordinate transformations or pixel blending

The graphics extensions were added as new packages under the AWT as the Java 2D API

The Java 2D Packages

• java.awt.color: Color control• java.awt.font: Fonts as complex shapes• java.awt.geom: Coordinate

transformations and shapes• java.awt.print: Advanced printing support

– Books, Pages and Paper

Java 2D API Features• Support for separate user and device

coordinate spaces

• Coordinates can be integers, floats or doubles

User Space Device Space

Java 2D API Features

• Support for coordinate transformations, for translation, rotation, scaling and shearing

User Space Device Space

Java 2D API Features

• Support for complex shapes and hit-testing

• Support for complex clipping

• More precise color control

• Support for variable transparency, allowing color blending

Java 2D API Features

• Better image-processing support, with convolution, color look-up, amplitude scaling.

• Improved screen updating, with offscreen buffers supporting BufferedImages and transparency

Basic Drawing

• The old Graphics context is still there

• All 2D drawing done using Graphics2D– Painting: typecasting Graphics into

Graphics2D

public void paint(Graphics g) {

Graphics2D g2d = (Graphics2D) g;

g2d.setColor(Color.red);

//…

}

Coordinate Transformations• Functions that map a point in one space

to a point in another space

• Represented using a 3x3 matrix

• Transformations require multiplying each pixel by a transformation matrix

• Positive angles rotate the X+ axis towards the Y+ axis

• Can be used to invert axes, bend images, distort space arbitrarily

Coordinate Transformations

a11 a12 a13

a21 a22 a23

0 0 1

x

y

1

a11x a12y a13

a21x a22y a23

0 0 1

x’

y’

1

= =

Affine Transforms• Maintain straightness and parallelism• Translation

• setToTranslation(double dx, double, dy);• used to support graphics scrolling

User Space Device Space

Affine Transforms• Rotation

– Rotating about the origin• setToRotation(double theta);

User Space Device Space

Affine Transforms

– Rotation about an arbitrary point• SetToRotation(theta, x, y);

User Space Device Space(x, y) (x, y)

Affine Transforms

• Shearing• setToShear(double sh, double sy)

User Space Device Space

Affine Transforms• Scaling

• setToScale(double sx, double sy)• anisotropic vs isotropic scaling

User Space Device Space

Using class AffineTransform• Commands can be cumulative

– concatenating transformations

• Commands are not commutative– Matrix multiplication is not commutative

• Dealing directly with the transformation matrix, to effect combined transformations in one pass

• g2D.setTransform(myAffineTransform);

Affine Transforms

• Handling transformed images with offscreen buffers

– Examples

• ScalingImages.java

• RotatingImages.java

• ShearingImages.java

Drawing with Paths• All 2D shapes are drawn as paths,

including lines and rectangles

• Class GeneralPath– Used to define arbitrary paths– The outline can be stroked– Graphics2D uses a default stroke:

• square pen• width is 1 pixel• continuous drawing - no dashes

Bezier curves• Used by the 2D API for cubic curves.

• Defined by simple control points

Drawing a Straight Line

public void paint(Graphics g) { Graphics2D g2d = (Graphics2D) g;

g2d.setColor(Color.red);

GeneralPath path =

new GeneralPath(GeneralPath.EVEN_ODD);

path.moveTo(50.0f, 50.0f);

path.lineTo(200.0f, 200.0f);

g2d.draw(path);

}

Drawing a Straight Line

Filling a shape public void paint(Graphics g) { Graphics2D g2d = (Graphics2D) g;

g2d.setColor(Color.blue);

GeneralPath path =

new GeneralPath(GeneralPath.EVEN_ODD);

path.moveTo(20.0f, 20.0f);

path.lineTo(100.0f, 20.0f);

path.lineTo(100.0f, 70.0f);

path.lineTo(20.0f, 70.0f);

path.closePath();

g2d.fill(path);

}

Filling a shape

Filling a Shape with a PatternBufferedImage image; // create a buffered image

Rectangle2D.Float rect = new Rectangle2D.Float(0.0f, 0.0f, 100.0f, 200.0f);

TexturePaint pattern =

new TexturePaint(image, rect,

TexturePaint.NEAREST_NEIGHBOR);

g2d.setPaint(pattern);

g2d.drawString(styledString, 10, 10);

Filling a Shape with a Pattern

Filling a Shape with an ImageImage image = getToolkit().getImage(url);

AffineTransform at = new AffineTransform();

at.setToTranslation(0, 200);

g2d.transform(at);

g2d.setClip(myShape);

at.setToTranslation(0, -200);

g2d.drawImage(image, at, this);

at.setToTranslation(0, 200);

g2d.setClip(null);

g2d.draw(myShape);

Filling a Shape with an Image

Filling a Shape with a Gradient Font myFont = new Font("Helvetica", Font.PLAIN, 200);

StyledString styledString =

new StyledString("AB", myFont);

Shape myShape = styledString.getStringOutline();

GradientPaint gradient =

new GradientPaint(0.0f, 0.0f, Color.red,

200.0f, 200.0f,

Color.yellow);

g2d.setPaint(gradient);

g2d.drawString(styledString, 10, 200);

Filling a Shape with a Gradient

Custom Strokes

• Class BasicStroke– simple to use– define common stroke properties

• width• end caps• line joins• dash attributes

Defining a Custom Stroke

g2d.setStroke(

new BasicStroke(penWidth,

BasicStroke.CAP_ROUND,

BasicStroke.JOIN_MITER ) );

path.moveTo(10.0f, 40.0f);

path.lineTo(90.0f, 40.0f);

g2d.draw(path);

Defining a Custom Stroke

2D Drawing Shortcuts

• interface Rectangle2D– Rectangle2D.Float– Rectangle2D.Double

• RoundRectangle2D

• Arc2D

• Ellipse2D

Clipping• Graphics2D.setClip(Path);• Clipping a circle with a rectangle Ellipse2D.Float circle = new Ellipse2D.Float(10.0f, 10.0f, 100.0f, 100.0f);

Rectangle2D.Float rect = new Rectangle2D.Float (10.0f, 30.0f, 100.0f, 70.0f);

g2d.setClip(rect);

g2d.setColor(Color.red);

g2d.fill(circle);

g2d.setClip(null);

g2d.setColor(Color.black);

g2d.draw(rect);

Clipping a Circle with a Rectangle

Clipping with TextFont myFont = new Font("Helvetica",Font.PLAIN,200);

StyledString styledString =

new StyledString("ABC", myFont);

Shape myShape = styledString.getStringOutline();

AffineTransform at = new AffineTransform();

at.setToTranslation(0, 200);

g2d.transform(at);

Ellipse2D.Float circle =

new Ellipse2D.Float(10.0f,-150.0f,400.0f,150.0f);

g2d.setClip(myShape);

g2d.setColor(Color.red);

g2d.fill(circle);

Clipping with Text

Blending objects– Transparency– The Alpha Channel – Compositing Operations

• called Raster Operations (ROP) in Windows• Class AlphaComposite

– Implements a subset of the Porter-Duff rules

Cd = Cs*Fs + Cd*Fd

Ad = As*Fs + Ad*Fd

C = Color d = destination

F = Fraction s = source

A = Alpha

Compositing Operations• Alpha=1 indicated total opaqueness

• Setting the Operation

AlphaComposite c = AlphaComposite.getInstance(

AlphaComposite.SRC_OVER,

0.5f);

g2d.setComposite(c);

Porter-Duff Operations Supported• CLEAR: destination cleared

• SRC: source copied to destination

• SRC_OVER: source is blended over dest

• SRC_IN: part of source already in dest replaces dest

• SRC_OUT: part of source not already in dest replaces dest

• DST_IN, DST_OUT, DEST_OVER

Using the SRC Rule

Using the SRC_OVER Rule

Using the SRC_IN Rule

Using the SRC_OUT Rule

Conclusion• The Java 2D API extends the AWT with:

– advanced geometric shapes– coordinate transformations– shapes of arbitrary complexity– text as a shape– arbitrary clipping regions– image blending through compositing– image processing capabilities– precise color control