Java: Detecting image format, resize (scale) and save as JPEG
11,927
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);
Once you've obtained your scaled Image
you can "convert" it back into a BufferedImage
as described here.
Finally, use the ImageIO
class to write your BufferedImage
to a file.
Author by
BoDiE2003
Updated on July 20, 2022Comments
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BoDiE2003 almost 2 years
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?
Thank you
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); } } }
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BoDiE2003 about 14 yearsThe scaling needs to be dynamic depending of the target Canvas container. Anyway, Ive solved it my self with a good refactoring and a couple of logic fixes. Thank you anyway
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Karussell about 12 yearslink does not work. hints for Image to BufferedImage transformation?
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Adamski about 12 yearsWhich link doesn't work? I just tried them all and they seem ok.
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jacobq over 10 yearsFYI: exampledepot.com/egs/java.awt.image/Image2Buf.html redirects to parked domain sites.
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Bruce Edge almost 10 yearsgetScaledInstance may not be your best friend: today.java.net/pub/a/today/2007/04/03/…