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 imagefinal 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;
}

代码来自google

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>

* 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
* @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;
}

压缩效果如下：

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baosoptions -= 10;// 每次都减少10image.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 imagefinal 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;
}

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