Java:检测图像格式，调整大小(缩放)并另存为 JPEG [英] Java: Detecting image format, resize (scale) and save as JPEG

问题描述

这是我的代码，它确实有效，但并不完美，但确实如此，问题是调整大小的缩略图没有粘贴在白色绘制的矩形上，破坏了图像的纵横比，这是代码，有人可以提出建议请给我一个修复，好吗?

This is the code I have, it actually works, not perfectly but it does, the problem is that the resized thumbnails are not pasting on the white Drawn rectangle, breaking the images aspect ratio, here is the code, could someone suggest me a fix for it, please?

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);
  }
 }

}

推荐答案

您可以使用 Image 的 getScaledInstance 方法:

You can easily scale your image by using Image's getScaledInstance method:

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);

获得缩放的Image 后，您可以将其转换"回BufferedImage 如此处.

Once you've obtained your scaled Image you can "convert" it back into a BufferedImage as described here.

最后，使用ImageIO 类将您的 BufferedImage 写入文件.

Finally, use the ImageIO class to write your BufferedImage to a file.

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