android 压缩图片大小，防止OOM

android开发中，图片的处理是非常普遍的，经常是需要将用户选择的图片上传到服务器，但是现在手机的分辨率越来越好了，随便一张照片都是2M或以上，如果直接显示到ImageView中，是会出现OOM的，上传到如服务器也会占用大量的流量，用户体验肯定不好了！

下面自己实现了图片的显示以及压缩功能，主要代码是从Volley的ImageRequest中copy过来，作为工具类方便以后图片处理

package com.img.util;import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.OutputStream;import android.content.Context;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Bitmap.CompressFormat;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore.Images;
import android.util.Log;/**
* 图片压缩工具类
*
* @author Administrator
*
*/
public class ImageCompress {public static final String CONTENT = "content";
public static final String FILE = "file";/**
* 图片压缩参数
*
* @author Administrator
*
*/
public static class CompressOptions {
public static final int DEFAULT_WIDTH = 400;
public static final int DEFAULT_HEIGHT = 800;public int maxWidth = DEFAULT_WIDTH;
public int maxHeight = DEFAULT_HEIGHT;
/**
* 压缩后图片保存的文件
*/
public File destFile;
/**
* 图片压缩格式,默认为jpg格式
*/
public CompressFormat imgFormat = CompressFormat.JPEG;/**
* 图片压缩比例 默认为30
*/
public int quality = 30;public Uri uri;
}public Bitmap compressFromUri(Context context,
CompressOptions compressOptions) {// uri指向的文件路径
String filePath = getFilePath(context, compressOptions.uri);if (null == filePath) {
return null;
}BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;Bitmap temp = BitmapFactory.decodeFile(filePath, options);int actualWidth = options.outWidth;
int actualHeight = options.outHeight;int desiredWidth = getResizedDimension(compressOptions.maxWidth,
compressOptions.maxHeight, actualWidth, actualHeight);
int desiredHeight = getResizedDimension(compressOptions.maxHeight,
compressOptions.maxWidth, actualHeight, actualWidth);options.inJustDecodeBounds = false;
options.inSampleSize = findBestSampleSize(actualWidth, actualHeight,
desiredWidth, desiredHeight);Bitmap bitmap = null;Bitmap destBitmap = BitmapFactory.decodeFile(filePath, options);// If necessary, scale down to the maximal acceptable size.
if (destBitmap.getWidth() > desiredWidth
|| destBitmap.getHeight() > desiredHeight) {
bitmap = Bitmap.createScaledBitmap(destBitmap, desiredWidth,
desiredHeight, true);
destBitmap.recycle();
} else {
bitmap = destBitmap;
}// compress file if need
if (null != compressOptions.destFile) {
compressFile(compressOptions, bitmap);
}return bitmap;
}/**
* compress file from bitmap with compressOptions
*
* @param compressOptions
* @param bitmap
*/
private void compressFile(CompressOptions compressOptions, Bitmap bitmap) {
OutputStream stream = null;
try {
stream = new FileOutputStream(compressOptions.destFile);
} catch (FileNotFoundException e) {
Log.e("ImageCompress", e.getMessage());
}bitmap.compress(compressOptions.imgFormat, compressOptions.quality,
stream);
}private static int findBestSampleSize(int actualWidth, int actualHeight,
int desiredWidth, int desiredHeight) {
double wr = (double) actualWidth / desiredWidth;
double hr = (double) actualHeight / desiredHeight;
double ratio = Math.min(wr, hr);
float n = 1.0f;
while ((n * 2) <= ratio) {
n *= 2;
}return (int) n;
}private static int getResizedDimension(int maxPrimary, int maxSecondary,
int actualPrimary, int actualSecondary) {
// If no dominant value at all, just return the actual.
if (maxPrimary == 0 && maxSecondary == 0) {
return actualPrimary;
}// If primary is unspecified, scale primary to match secondary's scaling
// ratio.
if (maxPrimary == 0) {
double ratio = (double) maxSecondary / (double) actualSecondary;
return (int) (actualPrimary * ratio);
}if (maxSecondary == 0) {
return maxPrimary;
}double ratio = (double) actualSecondary / (double) actualPrimary;
int resized = maxPrimary;
if (resized * ratio > maxSecondary) {
resized = (int) (maxSecondary / ratio);
}
return resized;
}/**
* 获取文件的路径
*
* @param scheme
* @return
*/
private String getFilePath(Context context, Uri uri) {String filePath = null;if (CONTENT.equalsIgnoreCase(uri.getScheme())) {Cursor cursor = context.getContentResolver().query(uri,
new String[] { Images.Media.DATA }, null, null, null);if (null == cursor) {
return null;
}try {
if (cursor.moveToNext()) {
filePath = cursor.getString(cursor
.getColumnIndex(Images.Media.DATA));
}
} finally {
cursor.close();
}
}// 从文件中选择
if (FILE.equalsIgnoreCase(uri.getScheme())) {
filePath = uri.getPath();
}return filePath;
}
}

使用方式：

<span style="white-space:pre"></span>ImageCompress compress = new ImageCompress();
ImageCompress.CompressOptions options = new ImageCompress.CompressOptions();
options.uri = imgUri;
options.maxWidth=getWindowManager().getDefaultDisplay().getWidth();
options.maxHeight=getWindowManager().getDefaultDisplay().getHeight();
Bitmap bitmap = compress.compressFromUri(this, options);

默认压缩比例为30%,可以根据实际情况修改。