Java 实现图片固定宽度缩放

1.方法一 jdk自带包

/**
     *
     * @param imageUrl 原图片地址
     * @param outFile 新图片文件
     * @param newWidth 指定宽度
     * @param quality 图片质量比(<1)
     */
    public static void resize(String imageUrl, File outFile, int newWidth, float quality) {
        if (quality > 1) {
            throw new IllegalArgumentException(
                    "Quality has to be between 0 and 1");
        }
        FileOutputStream out = null;
        try {
            File originalFile = new File(imageUrl);
            ImageIcon ii = new ImageIcon(originalFile.getCanonicalPath());
            Image i = ii.getImage();
            Image resizedImage = null;

            int iWidth = i.getWidth(null);
            int iHeight = i.getHeight(null);

            //if (iWidth > iHeight) {
            resizedImage = i.getScaledInstance(newWidth, (newWidth * iHeight)
                    / iWidth, Image.SCALE_SMOOTH);
        /*} else {
            resizedImage = i.getScaledInstance((newWidth * iWidth) / iHeight,
                    newWidth, Image.SCALE_SMOOTH);
        }*/

            // This code ensures that all the pixels in the image are loaded.
            Image temp = new ImageIcon(resizedImage).getImage();

            // Create the buffered image.
            BufferedImage bufferedImage = new BufferedImage(temp.getWidth(null),
                    temp.getHeight(null), BufferedImage.TYPE_INT_RGB);

            // Copy image to buffered image.
            Graphics g = bufferedImage.createGraphics();

            // Clear background and paint the image.
            g.setColor(Color.white);
            g.fillRect(0, 0, temp.getWidth(null), temp.getHeight(null));
            g.drawImage(temp, 0, 0, null);
            g.dispose();

            // Soften.
            float softenFactor = 0.05f;
            float[] softenArray = {0, softenFactor, 0, softenFactor,
                    1 - (softenFactor * 4), softenFactor, 0, softenFactor, 0};
            Kernel kernel = new Kernel(3, 3, softenArray);
            ConvolveOp cOp = new ConvolveOp(kernel, ConvolveOp.EDGE_NO_OP, null);
            bufferedImage = cOp.filter(bufferedImage, null);

            // Write the jpeg to a file.
            out = new FileOutputStream(outFile);
            ImageIO.write(bufferedImage, "jpg", out);
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (out != null) {
                try {
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

方法二     google之Thumbnails图片等比压缩

maven之pom.xml依赖

    net.coobird
    thumbnailator
    0.4.8

 

/**
     * @param imageUrl 原图片url
     * @param newWidth 压缩后宽度
     * @param quality  图片质量(<1)
     * @return
     */
public String imageZoom(String imageUrl, int newWidth, float quality) {
        ImageIcon imageIcon = new ImageIcon(imageUrl);
        int iconWidth = imageIcon.getIconWidth();
        int iconHeight = imageIcon.getIconHeight();
        try {
            //压缩后图片保存地址
            String imagePath = ""E:/PICTURE/4.jpg"
            Integer height = (newWidth * iconHeight) / iconWidth;
            Thumbnails.of(imageUrl).size(newWidth, height).outputQuality(quality).toFile(imagePath);
            return imagePath;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

更多方法可参考：https://blog.csdn.net/qq_33101675/article/details/75093372?depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-4&utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-4