如何在Graphics方法中使用ImageObserver drawImage()
我试图使用的方法是:drawImage(image,int,int,int,int,ImageObserver)方法,以便我可以扩展我的图像,在我看到的所有示例中,ImageObserver应该是这个,但这不是似乎工作(即我见过的唯一方法是:drawImage(image,int,int,ImageObserver),不知道这是否有所不同)。
这是我的主要类applet:
import java.applet.*; import java.awt.*; public class Main extends Applet implements Runnable{ private Thread th; private Hitter hitter; //double buffering private Graphics dbg; private Image dbImage; public void init(){ hitter = new Hitter(getImage(getCodeBase(), "Chitter.png")); } public void start(){ th = new Thread(this); th.start(); } public void stop(){ th.stop(); } public void update(Graphics g){ if(dbImage == null){ dbImage = createImage(this.getSize().width, this.getSize().width); dbg = dbImage.getGraphics(); } dbg.setColor(getBackground()); dbg.fillRect(0, 0, this.getSize().width, this.getSize().height); dbg.setColor(getForeground()); paint(dbg); g.drawImage(dbImage, 0, 0, this); } public void paint(Graphics g){ hitter.drawHitter(g); } public void run() { Thread.currentThread().setPriority(Thread.MIN_PRIORITY); while(true){ repaint(); try{ Thread.sleep(15); }catch(InterruptedException ex){} Thread.currentThread().setPriority(Thread.MAX_PRIORITY); } } public boolean mouseMove(Event e, int x, int y){ hitter.move(x); return true; } }
这是Hitter类:
import java.awt.*; import java.awt.image.ImageObserver; public class Hitter{ private int x, y; private Image hitter; private int hitterWidth = 50, hitterHeight = 10; private int appletsizeX = 500, appletsizeY = 500; Hitter(Image i){ hitter = i; start(); } public void drawHitter(Graphics g){ g.drawImage(hitter, x, y, hitterWidth, hitterHeight, this); } public void move(int a){ x = a; } public void start(){ x = appletsizeX/2 - hitterWidth/2; y = 0; } }
除非您调用Graphics.drawImage(Image, int, int, int, int, ImageObserver)
是ImageObserver
,否则使用this
作为ImageObserver
的参数将不起作用:
class MyClass { public void resizeImage() { Graphics g = getGraphicsObjectFromSomewhere(); // The following line will not compile, as `MyClass` // does not implement `ImageObserver`. g.drawImage(img, 0, 0, 50, 50, this); } }
如果要调整不需要ImageObserver
(例如已经包含要resize的图像的BufferedImage
),那么您只需移交null
:
// The image we want to resize BufferedImage img = ImageIO.read("some-image.jpg"); // The Graphics object of the destination // -- this will probably just be obtained from the destination image. Graphics g = getGraphicsObjectFromSomewhere(); // Perform the resizing. Hand a `null` for the ImageObserver, // as we don't need one. g.drawImage(img, 0, 0, 50, 50, null);
也就是说,我将为我的图像大小调整库Thumbnailator投入一点插件。
如果只需要调整图像大小,则可以像下面的代码一样简单地完成:
Thumbnails.of("path/to/image") .size(100, 100) .toFile("path/to/thumbnail");
Thumbnailator足够灵活,可以接受BufferedImage
, File
和InputStream
作为输入。
看到你的编辑,我建议改变Hitter
类,以便它将在构造函数中执行图像的大小调整。
由于您在drawHitter
每次调用中调用drawHitter
方法,因此使用Graphics.drawImage
的resize操作被多次调用,即使hitterWidth
和hitterHeight
是所有意图和目的的常量。
提前调整图像大小,并在drawHitter
方法中绘制预先resize的图像将更有效。