Java：检测图像格式，调整大小（缩放）并另存为 JPEG
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Java: Detecting image format, resize (scale) and save as JPEG
提问by BoDiE2003
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?
这是我拥有的代码，它实际上有效，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，有人可以建议我修复吗为了它，好吗？
Thank you
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);
}
}
}
回答by Adamski
You can easily scale your image by using Image's getScaledInstancemethod:
您可以使用Image'sgetScaledInstance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);
Once you've obtained your scaled Imageyou can "convert" it back into a BufferedImageas described here.
获得缩放后，Image您可以将其“转换”回此处BufferedImage所述。
Finally, use the ImageIOclass to write your BufferedImageto a file.
最后，使用ImageIO该类将您的内容写入BufferedImage文件。
