Android 显示获取服务器的超大图片 <19>

最新推荐文章于 2021-08-12 04:35:38 发布

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本文探讨了一种通过裁剪而非压缩图片来减小其大小并提高加载速度的方法，同时保持了图片的清晰度。具体介绍了使用MD5加密工具类和裁剪压缩类DurianBitmapCompress实现图片优化的过程。该方法适用于网络获取的图片，并通过保存到SD卡、压缩和返回显示用的Bitmap进行操作。同时，提到了考虑使用DiskLruCache策略以进一步优化大图片处理。

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最近看了网上面很多博客或者APP转发较多的一篇blog,说再也不用当心从服务器上面获取的图片有多大了,都能够轻松显示出来,不知道是不是没有仔细看那篇文章,还是什么,没有特别验证,感觉很奇怪,他不是通过压缩图片的方式显示,而是通过裁剪图片的方式然后显示出来,通过裁剪的方式压缩图片大小,个人觉得很奇怪,裁剪过的图片还有什么用呢?

个人结合前面的一篇博客,通过压缩的办法,然后在结合在网上面看了一些推荐的办法.

在没有去考虑DiskLruCache的方式,我粗略的操作如下:

首先提供一个MD5的工具类:DurianMD5.java

package org.durian.durianhttpresponsecache.bitmapcompress;

import java.security.MessageDigest;

/**
 * Project name : DurianHttpResponseCache
 * Created by zhibao.liu on 2016/1/29.
 * Time : 17:56
 * Email warden_sprite@foxmail.com
 * Action : durian
 */
public class DurianMD5 {

    /**
     * MD5加密
     * @param str 要加密的字符串
     * @return 加密后的字符串
     */
    public static String md5(String str) {
        MessageDigest md5 = null;
        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (Exception e) {
            e.printStackTrace();
            return "";
        }
        char[] charArray = str.toCharArray();
        byte[] byteArray = new byte[charArray.length];
        for (int i = 0; i < charArray.length; i++) {
            byteArray[i] = (byte) charArray[i];
        }
        byte[] md5Bytes = md5.digest(byteArray);
        StringBuffer hexValue = new StringBuffer();
        for (int i = 0; i < md5Bytes.length; i++) {
            int val = ((int) md5Bytes[i]) & 0xff;
            if (val < 16) {
                hexValue.append("0");
            }
            hexValue.append(Integer.toHexString(val));
        }
        return hexValue.toString();
    }

}

然后下面是一个DurianBitmapCompress.java

package org.durian.durianhttpresponsecache.bitmapcompress;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Rect;
import android.os.Environment;

import org.durian.durianhttpresponsecache.R;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Project name : DurianHttpResponseCache
 * Created by zhibao.liu on 2016/1/29.
 * Time : 17:54
 * Email warden_sprite@foxmail.com
 * Action : durian
 */
public class DurianBitmapCompress {

    final String PATH = Environment.getExternalStorageDirectory()
            + "/durian.jpg";

    public static Bitmap getCompressNetBitmap(Bitmap bitmap, int bitmapMaxWidth) throws Exception {

        String imagePath=saveToLocal(bitmap);

        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(imagePath, options);

        int height = options.outHeight;
        int width = options.outWidth;
        int reqHeight = 0;
        int reqWidth = bitmapMaxWidth;
        reqHeight = (reqWidth * height)/width;
        // 在内存中创建bitmap对象，这个对象按照缩放大小创建的
        options.inSampleSize = calculateInSampleSize(options, bitmapMaxWidth, reqHeight);
        options.inJustDecodeBounds = false;
        Bitmap map = BitmapFactory.decodeFile(imagePath, options);

        Bitmap retmap = compressImage(Bitmap.createScaledBitmap(map, bitmapMaxWidth, reqHeight, false));

        /*String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
                .format(new Date());
        saveImg(bbb, DurianMD5.md5(timeStamp));*/

        return retmap;

    }
    /*
    * how to use following code :
    * getCompressBitmap(context,480);
    * */
    public static Bitmap getCompressBitmap(Context context,int bitmapMaxWidth,int resID) throws Exception {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
//        BitmapFactory.decodeFile(oldPath, options);
        BitmapFactory.decodeResource(context.getResources(),resID,options);

        int height = options.outHeight;
        int width = options.outWidth;
        int reqHeight = 0;
        int reqWidth = bitmapMaxWidth;
        reqHeight = (reqWidth * height)/width;
        // 在内存中创建bitmap对象，这个对象按照缩放大小创建的
        options.inSampleSize = calculateInSampleSize(options, bitmapMaxWidth, reqHeight);
        options.inJustDecodeBounds = false;
//        Bitmap bitmap = BitmapFactory.decodeFile(oldPath, options);
        Bitmap bitmap =BitmapFactory.decodeResource(context.getResources(),resID,options);
        //Log.e("asdasdas", "reqWidth->"+reqWidth+"---reqHeight->"+reqHeight);
        Bitmap retmap = compressImage(Bitmap.createScaledBitmap(bitmap, bitmapMaxWidth, reqHeight, false));

        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
                .format(new Date());

//        saveImg(bbb, DurianMD5.md5(timeStamp));

        return retmap;
    }

    private static String getThumbUpFromDrawable(Context context, int bitmapMaxWidth) throws Exception {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
//        BitmapFactory.decodeFile(oldPath, options);
        BitmapFactory.decodeResource(context.getResources(),R.drawable.large,options);

        int height = options.outHeight;
        int width = options.outWidth;
        int reqHeight = 0;
        int reqWidth = bitmapMaxWidth;
        reqHeight = (reqWidth * height)/width;
        // 在内存中创建bitmap对象，这个对象按照缩放大小创建的
        options.inSampleSize = calculateInSampleSize(options, bitmapMaxWidth, reqHeight);
        options.inJustDecodeBounds = false;
//        Bitmap bitmap = BitmapFactory.decodeFile(oldPath, options);
        Bitmap bitmap =BitmapFactory.decodeResource(context.getResources(),R.drawable.large,options);
        //Log.e("asdasdas", "reqWidth->"+reqWidth+"---reqHeight->"+reqHeight);
        Bitmap retmap = compressImage(Bitmap.createScaledBitmap(bitmap, bitmapMaxWidth, reqHeight, false));
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
                .format(new Date());
        return saveImg(retmap, DurianMD5.md5(timeStamp));
    }

    /*
    * how to use following code :
    * getThumbUploadPath(PATH,480);
    * */

    private static String getThumbUploadPath(String oldPath,int bitmapMaxWidth) throws Exception {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(oldPath, options);
        int height = options.outHeight;
        int width = options.outWidth;
        int reqHeight = 0;
        int reqWidth = bitmapMaxWidth;
        reqHeight = (reqWidth * height)/width;
        // 在内存中创建bitmap对象，这个对象按照缩放大小创建的
        options.inSampleSize = calculateInSampleSize(options, bitmapMaxWidth, reqHeight);
        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeFile(oldPath, options);
        //Log.e("asdasdas", "reqWidth->"+reqWidth+"---reqHeight->"+reqHeight);
        Bitmap retmap = compressImage(Bitmap.createScaledBitmap(bitmap, bitmapMaxWidth, reqHeight, false));
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
                .format(new Date());
        return saveImg(retmap, DurianMD5.md5(timeStamp));
    }

    private static int calculateInSampleSize(BitmapFactory.Options options,
                                      int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {
            if (width > height) {
                inSampleSize = Math.round((float) height / (float) reqHeight);
            } else {
                inSampleSize = Math.round((float) width / (float) reqWidth);
            }
        }
        return inSampleSize;
    }

    private static Bitmap compressImage(Bitmap image) {

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        image.compress(Bitmap.CompressFormat.JPEG, 80, baos);// 质量压缩方法，这里100表示不压缩，把压缩后的数据存放到baos中
        int options = 100;
        while (baos.toByteArray().length / 1024 > 100) { // 循环判断如果压缩后图片是否大于100kb,大于继续压缩
            options -= 10;// 每次都减少10
            baos.reset();// 重置baos即清空baos
            image.compress(Bitmap.CompressFormat.JPEG, options, baos);// 这里压缩options%，把压缩后的数据存放到baos中
        }
        ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());// 把压缩后的数据baos存放到ByteArrayInputStream中
        Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);// 把ByteArrayInputStream数据生成图片
        return bitmap;
    }

    public static String saveToLocal(Bitmap map) throws Exception {
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
                .format(new Date());
        return saveImg(map, DurianMD5.md5(timeStamp));
    }

    public static String saveImg(Bitmap b,String name) throws Exception{
        String path = Environment.getExternalStorageDirectory().getPath()+File.separator+"";
        File mediaFile = new File(path + File.separator + name + ".jpg");
        if(mediaFile.exists()){
            mediaFile.delete();

        }
        if(!new File(path).exists()){
            new File(path).mkdirs();
        }
        mediaFile.createNewFile();
        FileOutputStream fos = new FileOutputStream(mediaFile);
        b.compress(Bitmap.CompressFormat.PNG, 100, fos);
        fos.flush();
        fos.close();
        /*b.recycle();
        b = null;
        System.gc();*/
        return mediaFile.getPath();
    }

}

上面的程序提供了很多API接口以便适应不同的环境.上面的程序需要注意几个地方:

第一个: 在保存的地方,下面如果最后一步是保存,图片不用于显示和其他用,就不需要注释下面的,以便回收memory,防止内存泄露,但是如果保存后,后面还要使用图片切记要屏蔽掉.

/*b.recycle();
        b = null;
        System.gc();*/

第二个:下面的这个方式从服务器获取图片后,先保存在sdcard目录下,然后对其提出压缩并且返回作为显示的Bitmap.

public static Bitmap getCompressNetBitmap(Bitmap bitmap, int bitmapMaxWidth)

网络获取:

if(connection.getResponseCode()==HttpURLConnection.HTTP_OK){

                        InputStream is=connection.getInputStream();
                        bitmap= BitmapFactory.decodeStream(is);
                        try {
                            bitmap=DurianBitmapCompress.getCompressNetBitmap(bitmap,450);
                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                    }

获取了以后通过发送一个Handler消息,更新图片.

刚才说了如果不考虑DiskLruCache,就直接保存在一个临时目录中,但是一般超大图片都会考虑使用DiskLruCache策略.DiskLruCache策略下一篇解释.