Contribute to rupali/book development by creating an account on GitHub. chapter begins by introducing many of Java's original drawing capabilities. Optional GUI and Graphics Case Study: Adding Java 2D | Making a Difference. In contrast, Listing illustrates the basic approach for drawing in Java 2D. All Next, cast the Graphics object to a Graphics2D object for Java 2D drawing.
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Drawing Review. A simple two-dimensional coordinate system exists for each graphics context or drawing surface such as a JPanel. Points on the. The screen is a 2D array of pixels. • A pixel (derived from picture element) is a single point of light displayed by the monitor. • The screen's origin is located at. Java 2D. • Review of Abstract Windows Toolkit (awt). • Java 2D graphical objects. • Java 2D awt has always provided a Graphics class - almost obsolete.
The simplest paint is java. Color , which generates the same color for all pixels. More complicated paints may produce gradients, images , or indeed any combination of colors. Filling a circular shape using the color yellow results in a solid yellow circle, while filling the same circular shape using a paint that generates an image produces a circular cutout of the image.
Composites[ edit ] During any drawing operation, there is a source the pixels being produced by the paint and a destination the pixels already onscreen. Normally, the source pixels simply overwrite the destination pixels, but the composite allows this behavior to be changed. The composite, given the source and destination pixels, produces the final result that ultimately ends up onscreen.
The most common composite is java. AlphaComposite , which can treat the pixels being drawn as partially transparent, so that the destination pixels show through to some degree. Filling[ edit ] To fill a shape, the first step is to identify which pixels fall inside the shape. These pixels will be affected by the fill operation.
Pixels that are partially inside and partially outside the shape may be affected to a lesser degree if anti-aliasing is enabled.
The paint is then asked to generate a color for each of the pixels to be painted. In the common case of a solid-color fill, each pixel will be set to the same color. We translate the rectangle up and left for the first ear, then to the right for the second ear. See the exercises at the end of this appendix for more example drawings.
RGB: A color model based on adding red, green, and blue light. See page?? Before you start the exercises, we recommend that you compile and run the examples.
Hint: You should only have to add or modify a few lines of code. Open it and read the paint method. Draw a sketch of what you expect it to do.
Now run it. Did you get what you expected? Modify the program so that the space between the circles is larger or smaller. See what happens to the image.
Play around and see what you can create. Consider the Rectangle2D class.
This is an abstract class with two concrete subclasses, which are also static inner classes: Rectangle2D. Float Rectangle2D. Double 2D rectangle classes It is best to try to ignore the fact that the two concrete classes are static inner classes— that is just a gimmick to avoid names such as Float Rectangle 2D and Double Rectangle 2D.
When you construct a Rectangle2D. Float object, you supply the coordinates as float numbers. For a Rectangle 2D. Double object, you supply them as double numbers.
Float Double Float and Rectangle 2D. Double extend the common Rectangle 2D class and the methods in the subclasses simply override methods in the Rectangle 2D superclass, there is no benefit in remembering the exact shape type. You cansimply use Rectangle2D variables to hold the rectangle references. The construction parameters denote the top-left corner, width, and height of therectangle. Float class has one additional method that is not inheritedfrom Rectangle2D, namely, setRect float x, float y, float h, float w.
You lose that method ifyou store the Rectangle 2D. Float reference in a Rectangle 2D variable.
But it is not a big loss—the Rectangle 2D class has a setRectmethod with double parameters. The Rectangle2D methods use double parameters and return values. For example, the get Width method returns a double value, even if the width is stored as a float in a Rectangle 2D.