画像の拡大・縮小

アフィン変換による拡大・縮小．

import java.awt.geom.AffineTransform; import java.awt.image.AffineTransformOp; import java.awt.image.BufferedImage; import java.io.File; import java.util.Iterator; import java.util.Locale; import javax.imageio.IIOImage; import javax.imageio.ImageIO; import javax.imageio.ImageWriteParam; import javax.imageio.ImageWriter; import javax.imageio.plugins.jpeg.JPEGImageWriteParam; import javax.imageio.stream.ImageOutputStream; public class ImageResize { public static void main(String[] args) throws Exception { File orgImageFile = new File("input.jpg"); BufferedImage orgImage = ImageIO.read(orgImageFile); int width = 320; int height = (int)(((double)width / orgImage.getWidth()) * (double)orgImage.getHeight()); BufferedImage resizeImage = new BufferedImage(width, height, orgImage.getType()); // ここからリサイズ処理 AffineTransformOp ato = null; ato = new AffineTransformOp( AffineTransform.getScaleInstance<a href="#f-6d4dd8bc" name="fn-6d4dd8bc" title="double)width / orgImage.getWidth(), (double) height / orgImage.getHeight(">*1</a>, null); ato.filter(orgImage, resizeImage); // ここまでリサイズ処理 ImageOutputStream imageStream = ImageIO.createImageOutputStream(new File("output.jpg")); ImageWriter writer = null; Iterator it = (Iterator) ImageIO.getImageWritersByFormatName("jpg"); writer = (ImageWriter) it.next(); writer.setOutput(imageStream); JPEGImageWriteParam jpgWriter = new JPEGImageWriteParam(Locale.getDefault()); jpgWriter.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); jpgWriter.setCompressionQuality(1f); writer.write(null, new IIOImage(resizeImage, null, null), jpgWriter); imageStream.flush(); writer.dispose(); imageStream.close(); } }

アフィン変換に引数指定．

// ここからリサイズ処理
		AffineTransformOp ato = null;
		ato = new AffineTransformOp(
                   AffineTransform.getScaleInstance((double)width / orgImage.getWidth(), 
				                                    (double) height / orgImage.getHeight()), 
				                                    AffineTransformOp.TYPE_BILINEAR);
		ato.filter(orgImage, resizeImage);
// ここまでリサイズ処理

面積平均法を利用した AreaAveragingScaleFilter による縮小。

// ここからリサイズ処理
		resizeImage.getGraphics().drawImage(
                  orgImage.getScaledInstance(width, height, Image.SCALE_AREA_AVERAGING), 
                    0, 0, width, height, null);
// ここまでリサイズ処理

*1:double)width / orgImage.getWidth(), (double) height / orgImage.getHeight(