1 Chapter 3 2D Graphics: Rendering Details  Color spaces, paints stroke types  Affine transforms including translation, rotation, scaling, shearing, and reflection  Object and viewing transformations  To identify the compositing rules  To use clipping path  To apply fonts and font metrics  To understand glyph, ligature, and derived font

2 Color Spaces  There are several models used for color –CIEXYZ - a color standard –RGB - used for monitors –CYMK - used for printers –sRGB - device-independent color space

3 RGB Colors  Color created by mixing light of different colors  This is what a CRT monitor uses  The Color class uses this model

4 CMY Colors  Color created by mixing ink/paint of different colors  This is how color on a a printer works

5 Creating Colors  To create a Color, give the amount of red, green and blue Color blue = new Color( 0, 0, 255); Color cyan = new Color( 0, 255, 255); Color black = new Color( 0, 0, 0); Color gray = new Color( 128, 128, 128); Color white = new Color( 255, 255, 255); Color hotPink = new Color( 255, 105, 180);

6 Setting Colors  The original AWT classes have two methods for controlling the color –Every component (including JPanel) has a background color public void setBackground( Color c)‏ –The graphics context has a color property  The current color is used for drawing and filling public void setColor( Color c)‏

7 Paint Interface Generalizing the concept of color, Java 2D drawing applies an attribute called paint

8 GradientPaint  Defines a Paint with varying colors  Specified by two points and two colors –at the first point, the color is the first color –at the second point, the color is the second color –in between, the color changes gradually –can be cyclic or acyclic (default)‏  an extra boolean parameter set to true creates a cyclic paint

9 TexturePaint  TexturePaint uses an image to tile the area being filled  Create with an image and an anchor rectangle –The anchor controls the positioning of the image TexturePaint( BufferImage image, Rectangle2D anchor)‏

10 Strokes  The Stroke interface defines a method for creating an outline from a shape  BasicStroke class has the following properties –Width –End style (butt, round, square)‏ –Join style (bevel, miter, round)‏ –Miter limit (limits miters on small angle joins)‏ –Dash pattern and phase

11 Dash Patterns  specified by an array of alternating on and off lengths –{10, 10} makes uniformly spaced dashes where the spaces are the same length as the dashes –{20, 5} makes equal-length dashes with a smaller space between them –{10, 5, 5, 5} makes a dot-dash pattern  The dash phase controls where in the pattern a line starts

12 Affine Transformation  Maps parallel lines to parallel lines  Common affine transforms –Translation –Rotation –Reflection –Scale –Shear

13 Isometry  An isometric transform preserves distances as well as parallel lines. –Also called Euclidean or rigid motions  Translation and rotation are isometries  Reflection is also an isometry  Shearing and scaling are not isometries

14 AffineTransform  All but translation can be represented by a 2x2 matrix  Using a 3x3 matrix allows translations to be represented by a matrix too  AffineTransform class has methods to set all but a refletion transform  Constructors and methods allow you to set the matrix directly

15 Translation  A translation moves an object (or a viewport)  Specified by how far to move in the x direction and the y direction void setToTranslate( double tx, double ty)‏

16 Translation Matrix 100 ty10 tx01

17 Rotation  Objects are rotated about the origin  Specified by an angle to rotate through  Rotations about other points are also possible void setToRotate( double theta )‏ void setToRotate( double theta, double x, double y)‏

18 Rotation Matrix cos  -sin  0 sin  cos 

19 Reflection  Map an object to its mirror image  To create a reflection, you need to specify the transformation matrix void setTransform( float m00, float m01, float m02, float m10, float m11, float m12)‏ AffineTransform(float m00, float m01, float m02, float m10, float m11, float m12)‏

20 General Reflection Matrix Reflection about line y = k x

21 Reflection Matrix Reflection about y-axis

22 Scaling  Scaling changes the size of an object  Shape is preserved if the scale factor is the same in both directions void setToScale( double sx, double sy)‏

23 Scaling Matrix 100 0sy0 00sx Scale by sx in x direction and sy in y direction

24 Shearing  Shifts points in an object by an amount that is proportional to ist distance from a specified line  Shape is not preserved void setToShear( double shx, double shy)‏

25 Scaling Matrix s1 Shear along x-axis by factor s

26 Composition of Transforms  Combine simple transforms to get more complicated ones  Matrix product is non-commutative

27 Clipping Path The rendered image may be clipped by a clipping path

28 Text in Java2D  Text is treated as a special kind of geometric object  A Font defines the rendering shapes of all the characters  One of the properties of a Graphics is a Font –Use the drawString method to display text –the current Font is used –use setFont (newFont) to change the font

29 Glyphs  The geometry describing the shape of an object is a Glyph  A glyph containing multiple letters is a ligature – A common ligature:

30 Font Class  Available fonts are platform (and machine) dependent  Logical fonts –Serif –SansSerif –Monospaced –Dialog –DialogInput  Font styles –PLAIN –ITALIC –BOLD  Derived font  Font metrics

The Font Class  A Font has three components –Font name –Font Style (add BOLD and ITALIC to get both)‏ –Font Size - integer number of points  Constructor takes three parameters Font( String fontFace, int fontStyle, int size)‏

Creating Fonts Font f1 = new Font( “SansSerif”, Font.BOLD, 24); Font f1 = new Font( “SansSerif”, Font.BOLD + Font.ITALIC, 16);

33 Deriving Fonts  If you have a Font, you can modify it to get new fonts –Use the getFont method to get the current font for a Graphics  Use one of the deriveFont factory methods to create a new font Font deriveFont( float size); Font deriveFont( int style); Font deriveFont( AffineTransform tr); … and several combinations

34 Font Measurements  Sometimes, you want to know how big a String will be when you draw it  Get a FontRenderContext for your Graphics2D object FontRenderContext getRenderContext ()‏  Use the getStringBounds method of the Font class to get the bounds of a string –The width and height of the bounds can be used to compute positions Rectangle2D = getStringBounds( String s, FontRenderContext frc);

35 Font Measurements  A LineMetrics object can be used to get more detailed information  Use the getLineMetrics method of the Font class to get the bounds of a string LineMetrics = getLineMetrics( String s, FontRenderContext frc);  The LineMetrics class has methods for getting measurements float getAscent()‏ float getLeading()‏ float getDescending()‏

36 Glyph  Sometimes you want to use some text as a clipping bounds  Geometry of a text string in a particular font is represented by a GlyphVector –Create a Shape from the GlyphVector  Example Font font = new Font("Serif", Font.BOLD, 144); FontRenderContext frc = g2.getFontRenderContext(); GlyphVector gv = font.createGlyphVector(frc, "Java"); Shape glyph = gv.getOutline(100,200);

37 Alpha Compositing  α-channel is used to simulate transparency in images –not all drawing contexts have an alpha channel  Color at a given point is a combination of the source and destination colors

38 A Probabilistic Model  α value as the probability of the color to be shown  Four different events: –source color occurs only -  s (1 -  d )‏ –destination color occurs only -  d (1 -  s )‏ –both colors occur -  s  d –neither color occurs. - (1 -  s ) (1 -  d )‏

39 Alpha Compositing  Porter-Duff came up with a set of 12 different rules that can be used. –based on probabilistic model  The AlphaComposite class incorporates these rues –one constant for each rule –Graphics2D has an AlphaComposite property  The rules don't all work in a Graphics object  They do work in BufferedImages

40 Porter-Duff Rules  Xor  DstOver  DstIn  DstOut  Dst  DstAtop  Clear  SrcOver  SrcIn  SrcOut  Src  SrcAtop