一個好用的android圖片壓縮工具類

 

 

 

用了很久圖片壓縮，之前人們一直使用google的官方圖片壓縮方法

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;
}

 

 

仔細看calucelateInSamplesize方法，該算法返回的是一種壓縮比例，仔細一看他的計算過程，你會發現，inSampleSize的變化過程是2-4-8,，而真正進入wile循環時，寬高就已經被看成是小了一半來計算的了，所以，上面那個網站說12M能壓縮到0.75M,就是因為差距太大，如果安卓手機內部壓縮自己的圖片(大概是2M壓縮到100K)，所以此時，這個方法就適用於android編碼壓縮了。

所以鄙人針對於android編碼時壓縮，在此對它進行了優化，優化後代碼如下：

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

 

/**

* 計算壓縮比例值(改進版 by touch_ping)
*
* 原版2>4>8...倍壓縮
* 當前2>3>4...倍壓縮
*
* @param options
* 解析圖片的配置信息
* @param reqWidth
* 所需圖片壓縮尺寸最小寬度
* @param reqHeight
* 所需圖片壓縮尺寸最小高度
* @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,壓縮: +inSampleSize + 倍);
inSampleSize += 1;
targetheight = picheight/inSampleSize;
targetwidth = picwidth/inSampleSize;
}
}

Log.i(test,最終壓縮比例: +inSampleSize + 倍);
Log.i(test, 新尺寸: + targetwidth + * +targetheight);
return inSampleSize;
}

 

文件大小從1.12M變成81.75k

 

 

 

最終附上完整壓縮工具類:

 

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;

/**
 * 圖片壓縮工具類
 * @author touch_ping
 * 2015-1-5 下午1:29:59
 */
public class BitmapCompressor {
	/**
	 * 質量壓縮
	 * @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(壓縮圖片);
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		image.compress(Bitmap.CompressFormat.JPEG, 50, baos);// 質量壓縮方法，這裡100表示不壓縮，把壓縮後的數據存放到baos中
		int options = 100;
//		Log.i(test,原始大小 + baos.toByteArray().length);
		while (baos.toByteArray().length / 1024 > maxkb) { // 循環判斷如果壓縮後圖片是否大於(maxkb)50kb,大於繼續壓縮
//			Log.i(test,壓縮一次!);
			baos.reset();// 重置baos即清空baos
			options -= 10;// 每次都減少10
			image.compress(Bitmap.CompressFormat.JPEG, options, baos);// 這裡壓縮options%，把壓縮後的數據存放到baos中
		}
//		Log.i(test,壓縮後大小 + baos.toByteArray().length);
		ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());// 把壓縮後的數據baos存放到ByteArrayInputStream中
		Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);// 把ByteArrayInputStream數據生成圖片
		return bitmap;
	}
	
	/**
	 * http://developer.android.com/training/displaying-bitmaps/load-bitmap.html
	 * 官網：獲取壓縮後的圖片
	 * 
	 * @param res
	 * @param resId
	 * @param reqWidth
	 *            所需圖片壓縮尺寸最小寬度
	 * @param reqHeight
	 *            所需圖片壓縮尺寸最小高度
	 * @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);
	}

	/**
	 * 官網：獲取壓縮後的圖片
	 * 
	 * @param res
	 * @param resId
	 * @param reqWidth
	 *            所需圖片壓縮尺寸最小寬度
	 * @param reqHeight
	 *            所需圖片壓縮尺寸最小高度
	 * @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);
	}

	/**
	 * 計算壓縮比例值(改進版 by touch_ping)
	 * 
	 * 原版2>4>8...倍壓縮
	 * 當前2>3>4...倍壓縮
	 * 
	 * @param options
	 *            解析圖片的配置信息
	 * @param reqWidth
	 *            所需圖片壓縮尺寸最小寬度O
	 * @param reqHeight
	 *            所需圖片壓縮尺寸最小高度
	 * @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,壓縮: +inSampleSize + 倍);
				inSampleSize += 1;
				targetheight = picheight/inSampleSize;
				targetwidth = picwidth/inSampleSize;
			}
		}
		
		Log.i(test,最終壓縮比例: +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;
}