平滑锯齿状路径

本文介绍了平滑锯齿状路径的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我参与了 有用:可读性强，是近期的，包括对以前工作的总结，并详细解释了他们的方法.

另见 涵盖相似背景的幻灯片 和 视频(！).

以下是最近邻居"与他们的技术"文档中的一些屏幕截图.

I was participating in the thread Image/Graphic into a Shape the other day and made a hackish attempt to get the outline of an image by adding a Rectangle iteratively to an Area. That was very slow.

This example instead builds a GeneralPath and creates the Area from the GP. Much faster.

The image on the upper left is the 'source image'. The two on the right are various stages of processing the outline. Both of them have jagged edges around the circle and along the slanted sides of the triangle.

I'd like to gain a shape that has that jaggedness removed or reduced.

In ASCII art. Case 1:

1234 1 ** 2 ** 3 *** 4 *** 5 **** 6 ****

Corners are at:

• (2,3) inner corner
• (3,3)
• (3,5) inner corner
• (4,5)

Case 2:

1234 1 **** 2 **** 3 ** 4 ** 5 **** 6 ****

Corners are at:

• (4,2)
• (2,2) inner corner
• (2,5) inner corner
• (4,5)

Assuming our path had the shapes shown, and the points as listed, I'd like to drop the 'inner corner' points of the first set, while retaining the 'pair' of inner corners (a bite out of the image) for the 2nd.

---

• Can anybody suggest some clever inbuilt method to do the heavy lifting of this job?
• Failing that, what would be a good approach to identifying the location & nature (pair/single) of the inner corners? (I'm guessing I could get a PathIterator and build a new GeneralPath dropping the singular inner corners - if only I could figure how to identify them!).

---

Here's the code to play with:

import java.awt.*; import java.awt.event.*; import java.awt.image.*; import java.awt.geom.*; import javax.swing.*; import javax.swing.border.*; import javax.swing.event.*; /* Gain the outline of an image for further processing. */ class ImageOutline { private BufferedImage image; private TwoToneImageFilter twoToneFilter; private BufferedImage imageTwoTone; private JLabel labelTwoTone; private BufferedImage imageOutline; private Area areaOutline = null; private JLabel labelOutline; private JLabel targetColor; private JSlider tolerance; private JProgressBar progress; private SwingWorker sw; public ImageOutline(BufferedImage image) { this.image = image; imageTwoTone = new BufferedImage( image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_RGB); } public void drawOutline() { if (areaOutline!=null) { Graphics2D g = imageOutline.createGraphics(); g.setColor(Color.WHITE); g.fillRect(0,0,imageOutline.getWidth(),imageOutline.getHeight()); g.setColor(Color.RED); g.setClip(areaOutline); g.fillRect(0,0,imageOutline.getWidth(),imageOutline.getHeight()); g.setColor(Color.BLACK); g.setClip(null); g.draw(areaOutline); g.dispose(); } } public Area getOutline(Color target, BufferedImage bi) { // construct the GeneralPath GeneralPath gp = new GeneralPath(); boolean cont = false; int targetRGB = target.getRGB(); for (int xx=0; xx<bi.getWidth(); xx++) { for (int yy=0; yy<bi.getHeight(); yy++) { if (bi.getRGB(xx,yy)==targetRGB) { if (cont) { gp.lineTo(xx,yy); gp.lineTo(xx,yy+1); gp.lineTo(xx+1,yy+1); gp.lineTo(xx+1,yy); gp.lineTo(xx,yy); } else { gp.moveTo(xx,yy); } cont = true; } else { cont = false; } } cont = false; } gp.closePath(); // construct the Area from the GP & return it return new Area(gp); } public JPanel getGui() { JPanel images = new JPanel(new GridLayout(2,2,2,2)); JPanel gui = new JPanel(new BorderLayout(3,3)); JPanel originalImage = new JPanel(new BorderLayout(2,2)); final JLabel originalLabel = new JLabel(new ImageIcon(image)); targetColor = new JLabel("Target Color"); targetColor.setForeground(Color.RED); targetColor.setBackground(Color.WHITE); targetColor.setBorder(new LineBorder(Color.BLACK)); targetColor.setOpaque(true); JPanel controls = new JPanel(new BorderLayout()); controls.add(targetColor, BorderLayout.WEST); originalLabel.addMouseListener( new MouseAdapter() { @Override public void mouseEntered(MouseEvent me) { originalLabel.setCursor( Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR)); } @Override public void mouseExited(MouseEvent me) { originalLabel.setCursor(Cursor.getDefaultCursor()); } @Override public void mouseClicked(MouseEvent me) { int x = me.getX(); int y = me.getY(); Color c = new Color( image.getRGB(x,y) ); targetColor.setBackground( c ); updateImages(); } }); originalImage.add(originalLabel); tolerance = new JSlider( JSlider.HORIZONTAL, 0, 255, 104 ); tolerance.addChangeListener( new ChangeListener() { public void stateChanged(ChangeEvent ce) { updateImages(); } }); controls.add(tolerance, BorderLayout.CENTER); gui.add(controls,BorderLayout.NORTH); images.add(originalImage); labelTwoTone = new JLabel(new ImageIcon(imageTwoTone)); images.add(labelTwoTone); images.add(new JLabel("Smoothed Outline")); imageOutline = new BufferedImage( image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_RGB ); labelOutline = new JLabel(new ImageIcon(imageOutline)); images.add(labelOutline); updateImages(); progress = new JProgressBar(); gui.add(images, BorderLayout.CENTER); gui.add(progress, BorderLayout.SOUTH); return gui; } private void updateImages() { if (sw!=null) { sw.cancel(true); } sw = new SwingWorker() { @Override public String doInBackground() { progress.setIndeterminate(true); adjustTwoToneImage(); labelTwoTone.repaint(); areaOutline = getOutline(Color.BLACK, imageTwoTone); drawOutline(); return ""; } @Override protected void done() { labelOutline.repaint(); progress.setIndeterminate(false); } }; sw.execute(); } public void adjustTwoToneImage() { twoToneFilter = new TwoToneImageFilter( targetColor.getBackground(), tolerance.getValue()); Graphics2D g = imageTwoTone.createGraphics(); g.drawImage(image, twoToneFilter, 0, 0); g.dispose(); } public static void main(String[] args) throws Exception { int size = 150; final BufferedImage outline = new BufferedImage(size,size,BufferedImage.TYPE_INT_RGB); Graphics2D g = outline.createGraphics(); g.setColor(Color.WHITE); g.fillRect(0,0,size,size); g.setRenderingHint( RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE); g.setRenderingHint( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); Polygon p = new Polygon(); p.addPoint(size/2, size/10); p.addPoint(size-10, size-10); p.addPoint(10, size-10); Area a = new Area(p); Rectangle r = new Rectangle(size/4, 8*size/10, size/2, 2*size/10); a.subtract(new Area(r)); int radius = size/10; Ellipse2D.Double c = new Ellipse2D.Double( (size/2)-radius, (size/2)-radius, 2*radius, 2*radius ); a.subtract(new Area(c)); g.setColor(Color.BLACK); g.fill(a); ImageOutline io = new ImageOutline(outline); JFrame f = new JFrame("Image Outline"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.add(io.getGui()); f.pack(); f.setResizable(false); f.setLocationByPlatform(true); f.setVisible(true); } } class TwoToneImageFilter implements BufferedImageOp { Color target; int tolerance; TwoToneImageFilter(Color target, int tolerance) { this.target = target; this.tolerance = tolerance; } private boolean isIncluded(Color pixel) { int rT = target.getRed(); int gT = target.getGreen(); int bT = target.getBlue(); int rP = pixel.getRed(); int gP = pixel.getGreen(); int bP = pixel.getBlue(); return( (rP-tolerance<=rT) && (rT<=rP+tolerance) && (gP-tolerance<=gT) && (gT<=gP+tolerance) && (bP-tolerance<=bT) && (bT<=bP+tolerance) ); } public BufferedImage createCompatibleDestImage( BufferedImage src, ColorModel destCM) { BufferedImage bi = new BufferedImage( src.getWidth(), src.getHeight(), BufferedImage.TYPE_INT_RGB); return bi; } public BufferedImage filter( BufferedImage src, BufferedImage dest) { if (dest==null) { dest = createCompatibleDestImage(src, null); } for (int x=0; x<src.getWidth(); x++) { for (int y=0; y<src.getHeight(); y++) { Color pixel = new Color(src.getRGB(x,y)); Color write = Color.BLACK; if (isIncluded(pixel)) { write = Color.WHITE; } dest.setRGB(x,y,write.getRGB()); } } return dest; } public Rectangle2D getBounds2D(BufferedImage src) { return new Rectangle2D.Double(0, 0, src.getWidth(), src.getHeight()); } public Point2D getPoint2D( Point2D srcPt, Point2D dstPt) { // no co-ord translation return srcPt; } public RenderingHints getRenderingHints() { return null; } }

解决方案

This is a big subject. You might find Depixelizing Pixel Art1 by Johannes Kopf & Dani Lischinski useful: it's readable, recent, includes a summary of previous work, and explains their approach in detail.

See also slides covering similar background and video(!).

Here are some screenshots from the document of 'nearest neighbor' vs. 'their technique'.