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。