Bagaimana Saya Boleh Meningkatkan Kualiti Imej Selepas Mengubah Saiz di Java?

Kualiti Imej Rendah Selepas Saiz semula dalam Java

Dalam skrip saiz semula imej yang mengurangkan imej daripada kira-kira 300x300 kepada 60x60, kualiti imej yang terhasil adalah tidak memuaskan.

Satu kaedah untuk meningkatkan kualiti adalah dengan menggunakan a pendekatan "pecah dan takluk". Daripada menskala imej dalam satu langkah, kaedah ini menskalakannya secara beransur-ansur dalam kenaikan 50% sehingga saiz yang dikehendaki dicapai. Proses penskalaan beransur-ansur ini membantu mengekalkan kualiti.

Kod Java berikut menunjukkan pendekatan bahagi dan takluk untuk mengubah saiz imej:

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

public class DivideAndConquerImageResize {

    public static void main(String[] args) {
        try {
            // Read the original image
            BufferedImage original = ImageIO.read(new File("master.jpg"));

            // Scale the image in 50% increments
            BufferedImage scaled = original;
            while (scaled.getWidth() > 60 || scaled.getHeight() > 60) {
                scaled = getScaledInstanceToFit(scaled, new Dimension(scaled.getWidth() / 2, scaled.getHeight() / 2));
            }

            // Write the scaled image to a file
            ImageIO.write(scaled, "jpg", new File("scaled.jpg"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static BufferedImage getScaledInstanceToFit(BufferedImage img, Dimension size) {
        float scaleFactor = getScaleFactorToFit(img, size);
        return getScaledInstance(img, scaleFactor);
    }

    public static float getScaleFactorToFit(BufferedImage img, Dimension size) {
        float scale = 1f;
        if (img != null) {
            int imageWidth = img.getWidth();
            int imageHeight = img.getHeight();
            scale = getScaleFactorToFit(new Dimension(imageWidth, imageHeight), size);
        }
        return scale;
    }

    public static float getScaleFactorToFit(Dimension original, Dimension toFit) {
        float scale = 1f;
        if (original != null && toFit != null) {
            float dScaleWidth = getScaleFactor(original.width, toFit.width);
            float dScaleHeight = getScaleFactor(original.height, toFit.height);
            scale = Math.min(dScaleHeight, dScaleWidth);
        }
        return scale;
    }

    public static float getScaleFactor(int iMasterSize, int iTargetSize) {
        float scale = 1;
        if (iMasterSize > iTargetSize) {
            scale = (float) iTargetSize / (float) iMasterSize;
        } else {
            scale = (float) iTargetSize / (float) iMasterSize;
        }
        return scale;
    }

    public static BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor) {
        BufferedImage imgBuffer = null;
        imgBuffer = getScaledInstance(img, dScaleFactor, RenderingHints.VALUE_INTERPOLATION_BILINEAR, true);
        return imgBuffer;
    }

    protected static BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor, Object hint, boolean higherQuality) {

        int targetWidth = (int) Math.round(img.getWidth() * dScaleFactor);
        int targetHeight = (int) Math.round(img.getHeight() * dScaleFactor);

        int type = (img.getTransparency() == Transparency.OPAQUE)
                ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;

        BufferedImage ret = (BufferedImage) img;

        if (targetHeight > 0 || targetWidth > 0) {
            int w, h;
            if (higherQuality) {
                w = img.getWidth();
                h = img.getHeight();
            } else {
                w = targetWidth;
                h = targetHeight;
            }

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

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

                BufferedImage tmp = new BufferedImage(Math.max(w, 1), Math.max(h, 1), type);
                Graphics2D g2 = tmp.createGraphics();
                g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
                g2.drawImage(ret, 0, 0, w, h, null);
                g2.dispose();

                ret = tmp;
            } while (w != targetWidth || h != targetHeight);
        } else {
            ret = new BufferedImage(1, 1, type);
        }
        return ret;
    }
}

Dengan menskala imej secara beransur-ansur, kaedah ini mengurangkan kesan secara berkesan artifak mampatan dan mengekalkan ketajaman imej.

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