一个好用的android图片压缩工具类

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">用了很久图片压缩，之前人们一直使用google的官方图片压缩方法</span>

final BitmapFactory.Options options = new BitmapFactory.Options();
		options.inJustDecodeBounds = true;
		BitmapFactory.decodeResource(res, resId, options);
		
		options.inSampleSize = calculateInSampleSize(options, reqWidth,
				reqHeight);
		options.inJustDecodeBounds = false;
		return BitmapFactory.decodeResource(res, resId, options);

public 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) {

        final int halfHeight = height / 2;
        final int halfWidth = width / 2;

        // Calculate the largest inSampleSize value that is a power of 2 and keeps both
        // height and width larger than the requested height and width.
        while ((halfHeight / inSampleSize) > reqHeight
                && (halfWidth / inSampleSize) > reqWidth) {
            inSampleSize *= 2;
        }
    }

    return inSampleSize;
}

http://developer.android.com/training/displaying-bitmaps/load-bitmap.html

仔细看calucelateInSamplesize方法，该算法返回的是一种压缩比例，仔细一看他的计算过程，你会发现，inSampleSize的变化过程是2-4-8,，而真正进入wile循环时，宽高就已经被看成是小了一半来计算的了，所以，上面那个网站说12M能压缩到0.75M,就是因为差距太大，如果安卓手机内部压缩自己的图片(大概是2M压缩到100K)，所以此时，这个方法就适用于android编码压缩了。

所以鄙人针对于android编码时压缩，在此对它进行了优化，优化后代码如下：

运行:   culculateInSampleSize(bm,200,300)效果:

<pre name="code" class="java"><span style="font-family: Arial, Helvetica, sans-serif;">/**</span>

文件大小从1.12M变成81.75k

最终附上完整压缩工具类:

package com.example.mqtest;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;

/**
 * 图片压缩工具类
 * @author touch_ping
 * 2015-1-5 下午1:29:59
 */
public class BitmapCompressor {
	/**
	 * 质量压缩
	 * @author ping 2015-1-5 下午1:29:58
	 * @param image
	 * @param maxkb
	 * @return
	 */
	public static Bitmap compressBitmap(Bitmap image,int maxkb) {
		//L.showlog("压缩图片");
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		image.compress(Bitmap.CompressFormat.JPEG, 50, 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;
//		Log.i("test","原始大小" + baos.toByteArray().length);
		while (baos.toByteArray().length / 1024 > maxkb) { // 循环判断如果压缩后图片是否大于(maxkb)50kb,大于继续压缩
//			Log.i("test","压缩一次!");
			baos.reset();// 重置baos即清空baos
			options -= 10;// 每次都减少10
			image.compress(Bitmap.CompressFormat.JPEG, options, baos);// 这里压缩options%，把压缩后的数据存放到baos中
		}
//		Log.i("test","压缩后大小" + baos.toByteArray().length);
		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;
	}
	
	/**
	 * http://developer.android.com/training/displaying-bitmaps/load-bitmap.html
	 * 官网：获取压缩后的图片
	 * 
	 * @param res
	 * @param resId
	 * @param reqWidth
	 *            所需图片压缩尺寸最小宽度
	 * @param reqHeight
	 *            所需图片压缩尺寸最小高度
	 * @return
	 */
	public static Bitmap decodeSampledBitmapFromResource(Resources res,
			int resId, int reqWidth, int reqHeight) {
		final BitmapFactory.Options options = new BitmapFactory.Options();
		options.inJustDecodeBounds = true;
		BitmapFactory.decodeResource(res, resId, options);
		
		options.inSampleSize = calculateInSampleSize(options, reqWidth,
				reqHeight);
		options.inJustDecodeBounds = false;
		return BitmapFactory.decodeResource(res, resId, options);
	}

	/**
	 * 官网：获取压缩后的图片
	 * 
	 * @param res
	 * @param resId
	 * @param reqWidth
	 *            所需图片压缩尺寸最小宽度
	 * @param reqHeight
	 *            所需图片压缩尺寸最小高度
	 * @return
	 */
	public static Bitmap decodeSampledBitmapFromFile(String filepath,
			int reqWidth, int reqHeight) {
		final BitmapFactory.Options options = new BitmapFactory.Options();
		options.inJustDecodeBounds = true;
		BitmapFactory.decodeFile(filepath, options);

		options.inSampleSize = calculateInSampleSize(options, reqWidth,
				reqHeight);
		options.inJustDecodeBounds = false;
		return BitmapFactory.decodeFile(filepath, options);
	}

	public static Bitmap decodeSampledBitmapFromBitmap(Bitmap bitmap,
			int reqWidth, int reqHeight) {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		bitmap.compress(Bitmap.CompressFormat.PNG, 90, baos);
		byte[] data = baos.toByteArray();
		
		final BitmapFactory.Options options = new BitmapFactory.Options();
		options.inJustDecodeBounds = true;
		BitmapFactory.decodeByteArray(data, 0, data.length, options);
		options.inSampleSize = calculateInSampleSize(options, reqWidth,
				reqHeight);
		options.inJustDecodeBounds = false;
		return BitmapFactory.decodeByteArray(data, 0, data.length, options);
	}

	/**
	 * 计算压缩比例值(改进版 by touch_ping)
	 * 
	 * 原版2>4>8...倍压缩
	 * 当前2>3>4...倍压缩
	 * 
	 * @param options
	 *            解析图片的配置信息
	 * @param reqWidth
	 *            所需图片压缩尺寸最小宽度O
	 * @param reqHeight
	 *            所需图片压缩尺寸最小高度
	 * @return
	 */
	public static int calculateInSampleSize(BitmapFactory.Options options,
			int reqWidth, int reqHeight) {
		
		final int picheight = options.outHeight;
		final int picwidth = options.outWidth;
		Log.i("test", "原尺寸:" +  picwidth + "*" +picheight);
		
		int targetheight = picheight;
		int targetwidth = picwidth;
		int inSampleSize = 1;
		
		if (targetheight > reqHeight || targetwidth > reqWidth) {
			while (targetheight  >= reqHeight
					&& targetwidth>= reqWidth) {
				Log.i("test","压缩:" +inSampleSize + "倍");
				inSampleSize += 1;
				targetheight = picheight/inSampleSize;
				targetwidth = picwidth/inSampleSize;
			}
		}
		
		Log.i("test","最终压缩比例:" +inSampleSize + "倍");
		Log.i("test", "新尺寸:" +  targetwidth + "*" +targetheight);
		return inSampleSize;
	}
}

public 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) {

        final int halfHeight = height / 2;
        final int halfWidth = width / 2;

        // Calculate the largest inSampleSize value that is a power of 2 and keeps both
        // height and width larger than the requested height and width.
        while ((halfHeight / inSampleSize) > reqHeight
                && (halfWidth / inSampleSize) > reqWidth) {
            inSampleSize *= 2;
        }
    }

    return inSampleSize;
}