AwtBicubicThumbnail.java

spring-boot/src/main/java/com/tutego/ch_02/beanQualification/thumbnail/AwtBicubicThumbnail.java

package com.tutego.ch_02.beanQualification.thumbnail;

import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Service;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UncheckedIOException;

@Order(0)
@Service("qualityThumbnailRenderer")
@ThumbnailRendering(ThumbnailRendering.RenderingQuality.QUALITY)
public class AwtBicubicThumbnail implements Thumbnail {

    private static BufferedImage create(BufferedImage source, int width, int height) {
        double thumbRatio = (double) width / height;
        double imageRatio = (double) source.getWidth() / source.getHeight();

        if (thumbRatio < imageRatio) height = (int) (width / imageRatio);
        else width = (int) (height * imageRatio);

        var thumb = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        var g2 = thumb.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
        g2.drawImage(source, 0, 0, width, height, null);
        g2.dispose();

        return thumb;
    }

    public byte[] thumbnail(byte[] imageBytes) {
        try (var is = new ByteArrayInputStream(imageBytes); var baos = new ByteArrayOutputStream()) {
            BufferedImage thumbnail = create(ImageIO.read(is), 200, 200);
            ImageIO.write(thumbnail, "jpg", baos);
            return baos.toByteArray();
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

}