この問題を調べましたが、システムクラスへの1回の呼び出しでこれを行う方法がわかりません。
Graphics2Dは、SunGraphics2Dとして実装された抽象インスタンスです。ソースコードは、たとえばdocjarで入手できるため、コードをコピーすることで、「同じことを行うが、異なる」可能性があります。ただし、画像をペイントするメソッドは、使用できない一部の「パイプ」クラスに依存します。クラスローディングを使用して作業を行いますが、理論的に最適なアプローチを実行するために操作できない、ネイティブで最適化されたクラスにヒットする可能性があります。あなたが得るのは正方形としてのイメージペインティングだけです。
ただし、独自の非ネイティブ（read：slow？）のコードをできるだけ実行せず、画像サイズに依存せず、丸い長方形の（比較的）低い領域に依存するアプローチを作成できます。また、メモリ内の画像をコピーせずに、大量のメモリを消費します。ただし、メモリが多い場合は、明らかに、インスタンスが作成された後、キャッシュされたイメージの方が高速です。
代替案1：
import java.awt.Composite;
import java.awt.CompositeContext;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import javax.swing.JLabel;
public class TPanel2 extends JLabel implements Composite, CompositeContext {
private int w = 300;
private int h = 200;
private int cornerRadius = 20;
private int[] roundRect; // first quadrant
private BufferedImage image;
private int[][] first = new int[cornerRadius][];
private int[][] second = new int[cornerRadius][];
private int[][] third = new int[cornerRadius][];
private int[][] forth = new int[cornerRadius][];
public TPanel2() {
setOpaque(false);
setPreferredSize(new Dimension(w, h));
setMaximumSize(new Dimension(w, h));
setMinimumSize(new Dimension(w, h));
// calculate round rect
roundRect = new int[cornerRadius];
for(int i = 0; i < roundRect.length; i++) {
roundRect[i] = (int)(Math.cos(Math.asin(1 - ((double)i)/20))*20); // x for y
}
image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB); // all black
}
@Override
public void paintComponent(Graphics g) {
// discussion:
// We have to work with the passed Graphics object.
if(g instanceof Graphics2D) {
Graphics2D g2d = (Graphics2D) g;
// draw the whole image and save the corners
g2d.setComposite(this);
g2d.drawImage(image, 0, 0, null);
} else {
super.paintComponent(g);
}
}
@Override
public CompositeContext createContext(ColorModel srcColorModel,
ColorModel dstColorModel, RenderingHints hints) {
return this;
}
@Override
public void dispose() {
}
@Override
public void compose(Raster src, Raster dstIn, WritableRaster dstOut) {
// lets assume image pixels >> round rect pixels
// lets also assume bulk operations are optimized
// copy current pixels
for(int i = 0; i < cornerRadius; i++) {
// quadrants
// from top to buttom
// first
first[i] = (int[]) dstOut.getDataElements(src.getWidth() - (cornerRadius - roundRect[i]), i, cornerRadius - roundRect[i], 1, first[i]);
// second
second[i] = (int[]) dstOut.getDataElements(0, i, cornerRadius - roundRect[i], 1, second[i]);
// from buttom to top
// third
third[i] = (int[]) dstOut.getDataElements(0, src.getHeight() - i - 1, cornerRadius - roundRect[i], 1, third[i]);
// forth
forth[i] = (int[]) dstOut.getDataElements(src.getWidth() - cornerRadius + roundRect[i], src.getHeight() - i - 1, cornerRadius - roundRect[i], 1, forth[i]);
}
// overwrite entire image as a square
dstOut.setRect(src);
// copy previous pixels back in corners
for(int i = 0; i < cornerRadius; i++) {
// first
dstOut.setDataElements(src.getWidth() - cornerRadius + roundRect[i], i, first[i].length, 1, second[i]);
// second
dstOut.setDataElements(0, i, second[i].length, 1, second[i]);
// third
dstOut.setDataElements(0, src.getHeight() - i - 1, third[i].length, 1, third[i]);
// forth
dstOut.setDataElements(src.getWidth() - cornerRadius + roundRect[i], src.getHeight() - i - 1, forth[i].length, 1, forth[i]);
}
}
}
代替案2：
import java.awt.AlphaComposite;
import java.awt.Composite;
import java.awt.CompositeContext;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import javax.swing.JLabel;
public class TPanel extends JLabel implements Composite, CompositeContext {
private int w = 300;
private int h = 200;
private int cornerRadius = 20;
private int[] roundRect; // first quadrant
private BufferedImage image;
private boolean initialized = false;
private int[][] first = new int[cornerRadius][];
private int[][] second = new int[cornerRadius][];
private int[][] third = new int[cornerRadius][];
private int[][] forth = new int[cornerRadius][];
public TPanel() {
setOpaque(false);
setPreferredSize(new Dimension(w, h));
setMaximumSize(new Dimension(w, h));
setMinimumSize(new Dimension(w, h));
// calculate round rect
roundRect = new int[cornerRadius];
for(int i = 0; i < roundRect.length; i++) {
roundRect[i] = (int)(Math.cos(Math.asin(1 - ((double)i)/20))*20); // x for y
}
image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB); // all black
}
@Override
public void paintComponent(Graphics g) {
if(g instanceof Graphics2D) {
Graphics2D g2d = (Graphics2D) g;
// draw 1 + 2 rectangles and copy pixels from image. could also be 1 rectangle + 4 edges
g2d.setComposite(AlphaComposite.Src);
g2d.drawImage(image, cornerRadius, 0, image.getWidth() - cornerRadius - cornerRadius, image.getHeight(), null);
g2d.drawImage(image, 0, cornerRadius, cornerRadius, image.getHeight() - cornerRadius - cornerRadius, null);
g2d.drawImage(image, image.getWidth() - cornerRadius, cornerRadius, image.getWidth(), image.getHeight() - cornerRadius, image.getWidth() - cornerRadius, cornerRadius, image.getWidth(), image.getHeight() - cornerRadius, null);
// draw the corners using our own logic
g2d.setComposite(this);
g2d.drawImage(image, 0, 0, null);
} else {
super.paintComponent(g);
}
}
@Override
public CompositeContext createContext(ColorModel srcColorModel,
ColorModel dstColorModel, RenderingHints hints) {
return this;
}
@Override
public void dispose() {
}
@Override
public void compose(Raster src, Raster dstIn, WritableRaster dstOut) {
// assume only corners need painting
if(!initialized) {
// copy image pixels
for(int i = 0; i < cornerRadius; i++) {
// quadrants
// from top to buttom
// first
first[i] = (int[]) src.getDataElements(src.getWidth() - cornerRadius, i, roundRect[i], 1, first[i]);
// second
second[i] = (int[]) src.getDataElements(cornerRadius - roundRect[i], i, roundRect[i], 1, second[i]);
// from buttom to top
// third
third[i] = (int[]) src.getDataElements(cornerRadius - roundRect[i], src.getHeight() - i - 1, roundRect[i], 1, third[i]);
// forth
forth[i] = (int[]) src.getDataElements(src.getWidth() - cornerRadius, src.getHeight() - i - 1, roundRect[i], 1, forth[i]);
}
initialized = true;
}
// copy image pixels into corners
for(int i = 0; i < cornerRadius; i++) {
// first
dstOut.setDataElements(src.getWidth() - cornerRadius, i, first[i].length, 1, second[i]);
// second
dstOut.setDataElements(cornerRadius - roundRect[i], i, second[i].length, 1, second[i]);
// third
dstOut.setDataElements(cornerRadius - roundRect[i], src.getHeight() - i - 1, third[i].length, 1, third[i]);
// forth
dstOut.setDataElements(src.getWidth() - cornerRadius, src.getHeight() - i - 1, forth[i].length, 1, forth[i]);
}
}
}
これがお役に立てば幸いです。これは次善の解決策ですが、それが人生です（これは、グラフィックの第一人者がやって来て、私が間違っていることを証明するときです（??）..）;-)
