Java：检测图像格式，resize（缩放）并另存为JPEG

这是我的代码，它实际上工作，不完美，但确实如此，问题是resize的缩略图不粘贴在白色的绘制矩形上，打破图像宽高比，这里是代码，有人可以建议我修复好吗，拜托？

谢谢

import java.awt.Color; import java.awt.Graphics2D; import java.awt.Image; import java.awt.RenderingHints; import java.awt.geom.Rectangle2D; import java.awt.image.BufferedImage; import java.io.BufferedInputStream; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import javax.imageio.ImageIO; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class ImageScalerImageIoImpl implements ImageScaler { private static final String OUTPUT_FORMAT_ID = "jpeg"; // Re-scaling image public byte[] scaleImage(byte[] originalImage, int targetWidth, int targetHeight) { try { InputStream imageStream = new BufferedInputStream( new ByteArrayInputStream(originalImage)); Image image = (Image) ImageIO.read(imageStream); int thumbWidth = targetWidth; int thumbHeight = targetHeight; // Make sure the aspect ratio is maintained, so the image is not skewed double thumbRatio = (double)thumbWidth / (double)thumbHeight; int imageWidth = image.getWidth(null); int imageHeight = image.getHeight(null); double imageRatio = (double)imageWidth / (double)imageHeight; if (thumbRatio < imageRatio) { thumbHeight = (int)(thumbWidth / imageRatio); } else { thumbWidth = (int)(thumbHeight * imageRatio); } // Draw the scaled image BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB); System.out.println("Thumb width Buffered: " + thumbWidth + " || Thumb height Buffered: " + thumbHeight); Graphics2D graphics2D = thumbImage.createGraphics(); // Use of BILNEAR filtering to enable smooth scaling graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR); // graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null); // White Background graphics2D.setPaint(Color.WHITE); graphics2D.fill(new Rectangle2D.Double(0, 0, targetWidth, targetHeight)); graphics2D.fillRect(0, 0, targetWidth, targetHeight); System.out.println("Target width: " + targetWidth + " || Target height: " + targetHeight); // insert the resized thumbnail between X and Y of the image graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null); System.out.println("Thumb width: " + thumbWidth + " || Thumb height: " + thumbHeight); // Write the scaled image to the outputstream ByteArrayOutputStream out = new ByteArrayOutputStream(); ImageIO.write(thumbImage, OUTPUT_FORMAT_ID, out); return out.toByteArray(); } catch (IOException ioe) { throw new ImageResizingException(ioe); } } } 

Answer 1

您可以使用Image的getScaledInstance方法轻松缩放图像：

 BufferedImage img = ImageIO.read(new File("image.jpg")); int scaleX = (int) (img.getWidth() * 0.5); int scaleY = (int) (img.getHeight() * 0.5); Image newImg = img.getScaledInstance(scaleX, scaleY, Image.SCALE_SMOOTH); 

获得缩放后的Image您可以将其“转换”回BufferedImage ，如此处所述。

最后，使用ImageIO类将BufferedImage写入文件。