how to resize Image in java?

Question

Hello I have a QR code Image , and I want to resize it , when I try to resize it to a small image using this code , I always get a blury image , and the QR code is no longer valid when I scan it , but it works fine when I resize to a big sized images with the same code :

public BufferedImage getScaledInstance(BufferedImage img,
                                   int targetWidth,
                                   int targetHeight,
                                   Object hint,
                                   boolean higherQuality)
{
int type = (img.getTransparency() == Transparency.OPAQUE) ?
    BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage)img;
int w, h;
if (higherQuality) {
    // Use multi-step technique: start with original size, then
    // scale down in multiple passes with drawImage()
    // until the target size is reached
    w = img.getWidth();
    h = img.getHeight();
} else {
    // Use one-step technique: scale directly from original
    // size to target size with a single drawImage() call
    w = targetWidth;
    h = targetHeight;
}

do {
    if (higherQuality && w > targetWidth) {
        w /= 2;
        if (w < targetWidth) {
            w = targetWidth;
        }
    }

    if (higherQuality && h > targetHeight) {
        h /= 2;
        if (h < targetHeight) {
            h = targetHeight;
        }
    }

    BufferedImage tmp = new BufferedImage(w, h, type);
    Graphics2D g2 = tmp.createGraphics();
    g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
    //        g2.setRenderingHint(RenderingHints.KEY_DITHERING, hint);
    g2.drawImage(ret, 0, 0, w, h, null);
    g2.dispose();

    ret = tmp;
} while (w != targetWidth || h != targetHeight);

return ret;
}

what is the problem , I don't exactly understand , please give me at least a hint , thank you

Livestock

You haven't shown a crucial detail -- what interpolation hint you are setting! – Monogenic

thanks a lot , my interpolation hint is RenderingHints.VALUE_INTERPOLATION_NEAREST_NEIGHBOR , I tried with all the possible values , still didn't work – Livestock

Answer 1

I use affine transformation to achieve this task, here is my code, hope it helps

/**
 * scale image
 * 
 * @param sbi image to scale
 * @param imageType type of image
 * @param dWidth width of destination image
 * @param dHeight height of destination image
 * @param fWidth x-factor for transformation / scaling
 * @param fHeight y-factor for transformation / scaling
 * @return scaled image
 */
public static BufferedImage scale(BufferedImage sbi, int imageType, int dWidth, int dHeight, double fWidth, double fHeight) {
    BufferedImage dbi = null;
    if(sbi != null) {
        dbi = new BufferedImage(dWidth, dHeight, imageType);
        Graphics2D g = dbi.createGraphics();
        AffineTransform at = AffineTransform.getScaleInstance(fWidth, fHeight);
        g.drawRenderedImage(sbi, at);
    }
    return dbi;
}

Blinking

Thanks a lot it works , but dude what to put in fWidth and fHeight ?, everytime I get different output – Livestock

those are the scale factors for the coordinates on the X and Y axis see the javadoc. for example if you want to have resulting image half a big as the original one so pass 0.5 for both fWidth and fHeight. Values less that 1 will scale down, values more than 1 will scale up, 1 will result in an image of the same dimensions. – Blinking

Thanks it solved my problem , I will choose this as the accepted answer , altough all the answers are accepted – Livestock

dWidth = sbi.getWidth()*fWidth and dHeight = sbi.getGeight()*fHeight – Birthright

@Blinking Reducing the size of an image to half its original size is not so simple, strictly speaking. For example: if you have an image that is a square in dimensions, reducing the width and height both by half will give you an image that is one quarter the size of the original image. You need to apply the Pythagorean theorem to get the desired dimensions: scale down c and solve for a and b for your actual desired height and width. – Translative

@Translative technically you are totally right, but generally speacking the size here mostly refers to the length of the dimensions. – Blinking

Answer 2

Based on @A4L's answer:

A more straigt forward version. Also his solution did only scale the canvas not the image itself.

public static BufferedImage scale(BufferedImage imageToScale, int dWidth, int dHeight) {
        BufferedImage scaledImage = null;
        if (imageToScale != null) {
            scaledImage = new BufferedImage(dWidth, dHeight, imageToScale.getType());
            Graphics2D graphics2D = scaledImage.createGraphics();
            graphics2D.drawImage(imageToScale, 0, 0, dWidth, dHeight, null);
            graphics2D.dispose();
        }
        return scaledImage;
    }

to increase the quality you could add

graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
graphics2D.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

Farewell

Also to increse quality one strategy could be to do the scalling in several small steps until the desired desired size is reached. – Blinking

True, called "Progressive Scaling" - I explain this here: #24745647 based on Campbell's blog: community.oracle.com/docs/DOC-983611 – Farewell

Answer 3

I wrote this class which i personally also use. I hope the code is straight forward.

import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.awt.image.CropImageFilter;
import java.awt.image.FilteredImageSource;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JComponent;


public class ImageScaler {

        private ImageIcon originalImage;
        private ImageIcon scaledImage;

        public ImageScaler(Image image) {
                this.originalImage = new ImageIcon(image);
        }

        public ImageScaler(String fileName) {
                originalImage = new ImageIcon(fileName);
        }

        public void createScaledImage(int size, ScalingDirection scalingDirection) {
                if (scalingDirection == ScalingDirection.HORIZONTAL) {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(size, -1, Image.SCALE_SMOOTH));
                } else {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, size, Image.SCALE_SMOOTH));
                }       
        }

        public void createScaledImage(int size, ScalingDirection scalingDirection, int scale) {
                if (scalingDirection == ScalingDirection.HORIZONTAL) {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(size, -1, scale));
                } else {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, size, scale));
                }
        }

        public void createScaledImage(int width, int height, ScaleType scaleType) {
                int imageWidth = originalImage.getImage().getWidth(null);
                int imageHeight = originalImage.getImage().getHeight(null);
                double originalImageRatio = imageWidth / (double) imageHeight;
                double scaledImageRatio = width / (double) height;

                if(scaleType == ScaleType.FIT) {
                        if(imageHeight - (Math.abs(imageWidth - width) / originalImageRatio) <= height) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(width, -1, Image.SCALE_SMOOTH));
                        } else if(imageWidth - (Math.abs(imageHeight - height) * originalImageRatio) <= width) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, height, Image.SCALE_SMOOTH));
                        }
                } else if(scaleType == ScaleType.FILL) {
                        if(imageHeight - (Math.abs(imageWidth - width) / originalImageRatio) >= height) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(width, -1, Image.SCALE_SMOOTH));
                                int thumbHeight = scaledImage.getImage().getHeight(null);

                                // Crop the image
                                scaledImage = new ImageIcon(Toolkit.getDefaultToolkit().createImage(new FilteredImageSource(scaledImage.getImage().getSource(), new CropImageFilter(0, (thumbHeight-height)/2, width, height))));
                        } else if(imageWidth - (Math.abs(imageHeight - height) * originalImageRatio) >= width) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, height, Image.SCALE_SMOOTH));
                                int thumbWidth = scaledImage.getImage().getWidth(null);

                                // Crop the image
                                scaledImage = new ImageIcon(Toolkit.getDefaultToolkit().createImage(new FilteredImageSource(scaledImage.getImage().getSource(), new CropImageFilter((thumbWidth-width)/2, 0, width, height))));
                        }               
                }
        }

        public void saveScaledImage(File file, ImageType imageType) {
                if (scaledImage != null) {
                        BufferedImage bi = new BufferedImage(scaledImage.getIconWidth(), scaledImage.getIconHeight(), BufferedImage.TYPE_INT_RGB);
                        Graphics g = bi.getGraphics();
                        g.drawImage(scaledImage.getImage(), 0, 0, null);
                        try {
                                ImageIO.write(bi, imageType.value(), file);
                        } catch (IOException ioe) {
                                System.out.println("Error occured saving scaled image");
                        }
                } else {
                        System.out.println("Scaled image has not yet been created");
                }
        }

        public void saveOriginalImage(File file, ImageType imageType) {
                if (originalImage != null) {
                        BufferedImage bi = new BufferedImage(originalImage.getIconWidth(), originalImage.getIconHeight(), BufferedImage.TYPE_INT_RGB);
                        Graphics g = bi.getGraphics();
                        g.drawImage(originalImage.getImage(), 0, 0, null);
                        try {
                                ImageIO.write(bi, imageType.value(), file);
                        } catch (IOException ioe) {
                                System.out.println("Error occured saving original image");
                        }
                } else {
                        System.out.println("Original image has not yet been created");
                }
        }

        // ENUMS
        public enum ScalingDirection {VERTICAL, HORIZONTAL};
        public enum ScaleType {FIT, FILL};
        public enum ImageType {
                IMAGE_JPEG ("jpeg"),
                IMAGE_JPG ("jpg"),
                IMAGE_PNG ("png");

                private String value = null;

                ImageType(String value) {
                        this.value = value;
                }

                String value() {
                        return value;
                }
        };
}   

Mystagogue

Thank you , I didn't try it because the code above worked, let the others give it a try . – Livestock

Answer 4

Please check this out Image.getScaledInstance() details can be found in this answer: How to improve the performance of g.drawImage() method for resizing images

Hope it helps

Sprage

Answer 5

    public static BufferedImage resizeImg(BufferedImage img, int newW, int newH)
    {
    int w = img.getWidth();
    int h = img.getHeight();
    BufferedImage dimg = new BufferedImage(newW, newH, img.getType());
    Graphics2D g = dimg.createGraphics();
    g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
            RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g.drawImage(img, 0, 0, newW, newH, 0, 0, w, h, null);
    g.dispose();
    return dimg;      
   }

Timer

Provide more information on how this code solves the OP's problem. It is unclear how this code helps. – Merce

Answer 6

I recommend Thumbnailnator because it gave me better quality images than the Java multi-step approach. The speed however might be better with your Graphics2D drawImage code.

See also Java - resize image without losing quality

Lelandleler

Answer 7

In fact, the solution is even more simple. You don't have to create a new BufferedImage. You can apply the method mentioned by for3st directly to the original BufferedImage image ('image') and set the width and height you wish for it. Thus a single statement is only needed (included in stadard Java documentation):

drawImage(BufferedImage image, int x, int y, int width, int height, ImageObserver observer) 

Curch