DefaultImageTool.java

package siscom.model.service.helper;

import static java.awt.Transparency.OPAQUE;
import static java.awt.image.BufferedImage.TYPE_INT_ARGB;
import static java.awt.image.BufferedImage.TYPE_INT_RGB;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.enterprise.context.Dependent;
import javax.imageio.ImageIO;

@Dependent
public class DefaultImageTool implements ImageTool {

	@Override
	public byte[] resizeCenteredPNG(final byte[] src, final int size) throws IOException {
		BufferedImage image = loadImage(src);

		if (image.getWidth() < size || image.getHeight() < size) {
			throw new IllegalStateException(String.format("Imagem não pode ser menor que %d pixels.", size));
		}

		if (image.getWidth() != image.getHeight()) {
			image = crop(image);
		}

		if (image.getWidth() != size || image.getHeight() != size) {
			image = resize(image, size);
		}

		return write(image);
	}

	protected BufferedImage crop(final BufferedImage srcImage) {
		final int newSize = Math.min(srcImage.getWidth(), srcImage.getHeight());
		final int x = (srcImage.getWidth() - newSize) / 2;
		final int y = (srcImage.getHeight() - newSize) / 2;
		return crop(srcImage, x, y, newSize, newSize);
	}

	protected BufferedImage crop(final BufferedImage src, final int x, final int y, final int width, final int height) {
		final BufferedImage result = createOptimalImage(src, width, height);
		final Graphics resultGraphics = result.getGraphics();

		resultGraphics.drawImage(src, 0, 0, width, height, x, y, x + width, y + height, null);
		resultGraphics.dispose();

		return result;
	}

	protected BufferedImage resize(final BufferedImage src, final int size) {
		final BufferedImage result = createOptimalImage(src, size, size);
		final Graphics2D resultGraphics = result.createGraphics();

		final Map<Object, Object> hints = new HashMap<>();
		hints.put(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
		hints.put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

		resultGraphics.setRenderingHints(hints);

		resultGraphics.drawImage(src, 0, 0, size, size, null);
		resultGraphics.dispose();

		return result;
	}

	protected byte[] write(final BufferedImage image) throws IOException {
		final ByteArrayOutputStream out = new ByteArrayOutputStream();
		ImageIO.write(image, "PNG", out);
		return out.toByteArray();
	}

	protected BufferedImage loadImage(final byte[] src) throws IOException {
		return ImageIO.read(new ByteArrayInputStream(src));
	}

	private BufferedImage createOptimalImage(final BufferedImage src, final int width, final int height) {
		return new BufferedImage(width, height, getImageType(src));
	}

	private int getImageType(final BufferedImage src) {
		return src.getTransparency() == OPAQUE ? TYPE_INT_RGB : TYPE_INT_ARGB;
	}
}

ImageTool.java

package siscom.model.service.helper;

import java.io.IOException;

public interface ImageTool {

	byte[] resizeCenteredPNG(byte[] src, int size) throws IOException;
}