Java改變圖片的大小

轉自：http://blog.csdn.net/mainstream_code/article/details/7036302

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<pre name="code" class="java">/**
 * 改變圖片的大小到寬爲size，然後高隨着寬等比例變化
 * @param is 上傳的圖片的輸入流
 * @param os 改變了圖片的大小後，把圖片的流輸出到目標OutputStream
 * @param size 新圖片的寬
 * @param format 新圖片的格式
 * @throws IOException
 */
public static void resizeImage(InputStream is, OutputStream os, int size, String format) throws IOException {
    BufferedImage prevImage = ImageIO.read(is);
    double width = prevImage.getWidth();
    double height = prevImage.getHeight();
    double percent = size/width;
    int newWidth = (int)(width * percent);
    int newHeight = (int)(height * percent);
    BufferedImage image = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_BGR);
    Graphics graphics = image.createGraphics();
    graphics.drawImage(prevImage, 0, 0, newWidth, newHeight, null);
    ImageIO.write(image, format, os);
    os.flush();
    is.close();
    os.close();
}  </pre><br>
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<pre name="code" class="java"></pre><pre name="code" class="java"></pre><pre name="code" class="java"></pre><pre name="code" class="java"></pre><pre name="code" class="java">package graphicsTest;

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

import javax.imageio.ImageIO;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class GraphicsTest1 {

    // 圖片寬和高的最大尺寸
    public static final int IMAGEMAXBIG = 2000;
    // 圖片寬和高的最小尺寸
    public static final int IMAGEMINBIG = 10;
    // 按原圖大小生成新圖
    public static final int CREATENEWIMAGETYPE_0 = 0;
    // 按指定的大小生成新圖
    public static final int CREATENEWIMAGETYPE_1 = 1;
    // 按原圖寬高比例生成新圖-按指定的寬度
    public static final int CREATENEWIMAGETYPE_2 = 2;
    // 按原圖寬高比例生成新圖-按指定的高度
    public static final int CREATENEWIMAGETYPE_3 = 3;
    // 按原圖寬高比例生成新圖-按指定的寬和高中較大的尺寸
    public static final int CREATENEWIMAGETYPE_4 = 4;
    // 按原圖寬高比例生成新圖-按指定的寬和高中較小的尺寸
    public static final int CREATENEWIMAGETYPE_5 = 5;

    /**
     *
     * @param _file
     *            原圖片
     * @param createType
     *            處理類型
     * @param newW
     *            新寬度
     * @param newH
     *            新高度
     * @return
     * @throws Exception
     */
    public static String createNewImage(File _file, int createType, int newW,
            int newH) throws Exception {
        if (_file == null)
            return null;
        String fileName = _file.getPath();
        if (fileName == null || "".equals(fileName)
                || fileName.lastIndexOf(".") == -1)
            return null;
        String newFileName = "_NEW";
        /*
         * else newFileName = "_" + newFileName;
         */

        String outFileName = fileName.substring(0, fileName.lastIndexOf("."))
                + newFileName
                + fileName.substring(fileName.lastIndexOf("."), fileName
                        .length());
        String fileExtName = fileName.substring(
                (fileName.lastIndexOf(".") + 1), fileName.length());
        if (newW < IMAGEMINBIG)
            newW = IMAGEMINBIG;
        else if (newW > IMAGEMAXBIG)
            newW = IMAGEMAXBIG;

        if (newH < IMAGEMINBIG)
            newH = IMAGEMINBIG;
        else if (newH > IMAGEMAXBIG)
            newH = IMAGEMAXBIG;

        // 得到原圖信息
        if (!_file.exists() || !_file.isAbsolute() || !_file.isFile()
                || !checkImageFile(fileExtName))
            return null;
        if ((new File(outFileName)).exists()) {
            System.out.println("file [" + outFileName + "] already exists");
            throw new Exception();
        }
        Image src = ImageIO.read(_file);
        int w = src.getWidth(null);
        int h = src.getHeight(null);

        // 確定目標圖片的大小
        int nw = w;
        int nh = h;
        if (createType == CREATENEWIMAGETYPE_0)
            ;
        else if (createType == CREATENEWIMAGETYPE_1) {
            nw = newW;
            nh = newH;
        } else if (createType == CREATENEWIMAGETYPE_2) {
            nw = newW;
            nh = (int) ((double) h / (double) w * nw);
        } else if (createType == CREATENEWIMAGETYPE_3) {
            nh = newH;
            nw = (int) ((double) w / (double) h * nh);
        } else if (createType == CREATENEWIMAGETYPE_4) {
            if ((double) w / (double) h >= (double) newW / (double) newH) {
                nh = newH;
                nw = (int) ((double) w / (double) h * nh);
            } else {
                nw = newW;
                nh = (int) ((double) h / (double) w * nw);
            }
        } else if (createType == CREATENEWIMAGETYPE_5) {
            if ((double) w / (double) h <= (double) newW / (double) newH) {
                nh = newH;
                nw = (int) ((double) w / (double) h * nh);
            } else {
                nw = newW;
                nh = (int) ((double) h / (double) w * nw);
            }
        }

        // 構造目標圖片
        BufferedImage tag = new BufferedImage(nw, nh,
                BufferedImage.TYPE_INT_RGB);

        // 得到目標圖片輸出流
        FileOutputStream out = new FileOutputStream(outFileName);

        // 根據需求畫出目標圖片 方式1
        tag.getGraphics().drawImage(src, 0, 0, nw, nh, null);

        // 將畫好的目標圖輸出到輸出流 方式1
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        encoder.encode(tag);
        out.close();
        return outFileName;
    }

    public static boolean checkImageFile(String extName) {

        if ("jpg".equalsIgnoreCase(extName))
            return true;
        if ("gif".equalsIgnoreCase(extName))
            return true;
        if ("bmp".equalsIgnoreCase(extName))
            return true;
        if ("jpeg".equalsIgnoreCase(extName))
            return true;
        if ("png".equalsIgnoreCase(extName))
            return true;
        return false;
    }

}  </pre>
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