Java 裁剪图片

package com.test;

import java.awt.image.BufferedImage;
import java.io.File;

import javax.imageio.ImageIO;

public class Test {
        private static final double WORK_LOAD_FACTOR = 0.265;

        private static final double LANCZOS_SUPPORT = 3;
        private static final double LANCZOS_WINDOW = 3;
        private static final double LANCZOS_SCALE = 1;
        private static final double LANCZOS_BLUR = 1;

        private static final double EPSILON = 1.0e-6;

        private static class ContributionInfo {
            private double weight;
            private int pixel;
        }

        public static BufferedImage resizeImage(BufferedImage image, double ratio) {
            return resizeImage(image, (int)(image.getWidth() * ratio + 0.5), (int)(image.getHeight() * ratio + 0.5));
        }

        public static BufferedImage resizeImage(BufferedImage image, double xRatio, double yRatio) {
            return resizeImage(image, (int)(image.getWidth() * xRatio + 0.5), (int)(image.getHeight() * yRatio + 0.5));
        }

        public static BufferedImage resizeImage(BufferedImage image, int width, int height) {
            double xFactor = width * 1.0 / image.getWidth();
            double yFactor = height * 1.0 / image.getHeight();

            BufferedImage resizeImage = new BufferedImage(width, height, image.getType());
            BufferedImage filterImage = null;

            if (xFactor * yFactor > WORK_LOAD_FACTOR) {
                filterImage = new BufferedImage(width, image.getHeight(), image.getType());
                horizontalFilter(image, filterImage, xFactor);
                verticalFilter(filterImage, resizeImage, yFactor);
            } else {
                filterImage = new BufferedImage(image.getWidth(), height, image.getType());
                verticalFilter(image, filterImage, yFactor);
                horizontalFilter(filterImage, resizeImage, xFactor);
            }
            return resizeImage;
        }

        private static void verticalFilter(BufferedImage image, BufferedImage resizeImage,
                double yFactor) {
            double scale = Math.max(1.0 / yFactor, 1.0);
            double support = scale * LANCZOS_SUPPORT;
            if (support < 0.5) {
                support = 0.5;
                scale = 1.0;
            }
            scale = 1.0 / scale;

            for (int y = 0; y < resizeImage.getHeight(); y++) {
                double center = (y + 0.5) / yFactor;
                int start = (int) (Math.max(center - support - EPSILON, 0.0) + 0.5);
                int stop = (int) (Math.min(center + support, image.getHeight()) + 0.5);
                double density = 0.0;
                ContributionInfo[] contribution = new ContributionInfo[stop - start];
                int n;
                for (n = 0; n < (stop - start); n++) {
                    contribution[n] = new ContributionInfo();
                    contribution[n].pixel = start + n;
                    contribution[n].weight = getResizeFilterWeight(scale * (start + n - center + 0.5));
                    density += contribution[n].weight;
                }

                if ((density != 0.0) && (density != 1.0)) {
                    density = 1.0 / density;
                    for (int i = 0; i < n; i++)
                        contribution[i].weight *= density;
                }
                for (int x = 0; x < resizeImage.getWidth(); x++) {
                    double red = 0;
                    double green = 0;
                    double blue = 0;
                    for (int i = 0; i < n; i++) {
                        double alpha = contribution[i].weight;
                        int rgb = image.getRGB(x, contribution[i].pixel);
                        red += alpha * ((rgb >> 16) & 0xFF);
                        green += alpha * ((rgb >> 8) & 0xFF);
                        blue += alpha * (rgb & 0xFF);
                    }
                    int rgb = roundToQuantum(red) << 16 | roundToQuantum(green) << 8
                            | roundToQuantum(blue);
                    resizeImage.setRGB(x, y, rgb);
                }
            }
        }

        private static void horizontalFilter(BufferedImage image, BufferedImage resizeImage,
                double xFactor) {
            double scale = Math.max(1.0 / xFactor, 1.0);
            double support = scale * LANCZOS_SUPPORT;
            if (support < 0.5) {
                support = 0.5;
                scale = 1.0;
            }
            scale = 1.0 / scale;

            for (int x = 0; x < resizeImage.getWidth(); x++) {
                double center = (x + 0.5) / xFactor;
                int start = (int) (Math.max(center - support - EPSILON, 0.0) + 0.5);
                int stop = (int) (Math.min(center + support, image.getWidth()) + 0.5);
                double density = 0.0;
                ContributionInfo[] contribution = new ContributionInfo[stop - start];
                int n;
                for (n = 0; n < (stop - start); n++) {
                    contribution[n] = new ContributionInfo();
                    contribution[n].pixel = start + n;
                    contribution[n].weight = getResizeFilterWeight(scale * (start + n - center + 0.5));
                    density += contribution[n].weight;
                }

                if ((density != 0.0) && (density != 1.0)) {
                    density = 1.0 / density;
                    for (int i = 0; i < n; i++)
                        contribution[i].weight *= density;
                }
                for (int y = 0; y < resizeImage.getHeight(); y++) {
                    double red = 0;
                    double green = 0;
                    double blue = 0;
                    for (int i = 0; i < n; i++) {
                        double alpha = contribution[i].weight;
                        int rgb = image.getRGB(contribution[i].pixel, y);
                        red += alpha * ((rgb >> 16) & 0xFF);
                        green += alpha * ((rgb >> 8) & 0xFF);
                        blue += alpha * (rgb & 0xFF);
                    }
                    int rgb = roundToQuantum(red) << 16 | roundToQuantum(green) << 8
                            | roundToQuantum(blue);
                    resizeImage.setRGB(x, y, rgb);
                }
            }
        }

        private static double getResizeFilterWeight(double x) {
            double blur = Math.abs(x) / LANCZOS_BLUR;
            double scale = LANCZOS_SCALE / LANCZOS_WINDOW;
            scale = sinc(blur * scale);
            return scale * sinc(blur);
        }

        private static double sinc(double x) {
            if (x == 0.0)
                return 1.0;
            return Math.sin(Math.PI * x) / (Math.PI * x);
        }

        private static int roundToQuantum(double value) {
            if (value <= 0.0)
                return 0;
            if (value >= 255)
                return 255;
            return (int) (value + 0.5);
        }

        public static void main(String[] args) throws Exception {
            BufferedImage image = ImageIO.read(new File("C:/Users/admin/Desktop/efg.jpg"));
            ImageIO.write(resizeImage(image, 100, 100), "PNG", new File("C:/Users/admin/Desktop/sefg.jpg"));
        }

}