java 缩略图

先看下效果图

1.PNG

/**
 * 图片压缩处理.
 */
public final class ImgCompressUtil {

    private ImgCompressUtil() {
    }

    /**
     * 强制压缩/放大图片到固定的大小.
     *
     * @param fileName        压缩文件("d:\\1.png")
     * @param compressPercent 压缩比例(压缩为原来一半传0.5)
     * @return BufferedImage bufferImage
     */
    public static BufferedImage resize(String fileName, double compressPercent) {
        BufferedImage img = null; //原图
        BufferedImage compressImg = null; //压缩后图
        int width;
        int height;
        try {
            File file = new File(fileName);
            img = ImageIO.read(file);
            width = (int) (img.getWidth() * compressPercent);
            height = (int) (img.getHeight() * compressPercent);
            compressImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            compressImg.getGraphics().drawImage(img, 0, 0, width, height, null); // 绘制缩小后的图
        } catch (IOException e) {
            e.printStackTrace();
        }
        return compressImg;
    }

    /**
     * bufferImage 转 file.
     *
     * @param file 存放位置("d: \\1.png")
     * @param img  buggerImage
     */
    public static void writeToFile(String file, BufferedImage img) {
        try {
            File destFile = new File(file);
            FileOutputStream out = new FileOutputStream(destFile); // 输出到文件流
            ImageIO.write(img, "png", out);
            out.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

测试

    @Test
    public void pictureCompress() {
        String fileName = "D:\\cp.png";

        BufferedImage bufferedImage = ImgCompressUtil.resize("D:\\1.png", 0.5);
        ImgCompressUtil.writeToFile(fileName + "_middle.png", bufferedImage);

        BufferedImage bufferedImage2 = ImgCompressUtil.resize("D:\\1.png", 0.25);
        ImgCompressUtil.writeToFile(fileName + "_small.png", bufferedImage2);
    }

这里有个小技巧，也就是默认的约定，0.5倍缩略图的名字就是原图名字+_middle.png，0.25倍缩略图的名字就是原图名字+_small.png