ANDROID图片压缩代码

  2 

  3 import java.io.FileDescriptor;

  4 import java.io.FileInputStream;

  5 

  6 import android.graphics.Bitmap;

  7 import android.graphics.BitmapFactory;

  8 

  9 /**

 10  * 图片处理类   压缩

 11  * 

 12  * @author Administrator

 13  * 

 14  */

 15 public class ImageUtil {

 16     /**

 17      * get Bitmap

 18      * 

 19      * @param imgPath

 20      * @param minSideLength

 21      * @param maxNumOfPixels

 22      * @return

 23      */

 24     public static Bitmap getBitmap(String imgPath, int minSideLength,

 25             int maxNumOfPixels) {

 26         if (imgPath == null || imgPath.length() == 0)

 27             return null;

 28 

 29         try {

 30             FileDescriptor fd = new FileInputStream(imgPath).getFD();

 31             BitmapFactory.Options options = new BitmapFactory.Options();

 32             options.inJustDecodeBounds = true;

 33             // BitmapFactory.decodeFile(imgFile, options);

 34             BitmapFactory.decodeFileDescriptor(fd, null, options);

 35 

 36             options.inSampleSize = computeSampleSize(options,

 37                     minSideLength, maxNumOfPixels);

 38             try {

 39                 // 这里一定要将其设置回false，因为之前我们将其设置成了true

 40                 // 设置inJustDecodeBounds为true后，decodeFile并不分配空间，即，BitmapFactory解码出来的Bitmap为Null,但可计算出原始图片的长度和宽度

 41                 options.inJustDecodeBounds = false;

 42 

 43                 Bitmap bmp = BitmapFactory.decodeFile(imgPath, options);

 44                 return bmp == null ? null : bmp;

 45             } catch (OutOfMemoryError err) {

 46                 return null;

 47             }

 48         } catch (Exception e) {

 49             return null;

 50         }

 51     }

 52 

 53     /**

 54      * compute Sample Size

 55      * 

 56      * @param options

 57      * @param minSideLength

 58      * @param maxNumOfPixels

 59      * @return

 60      */

 61     private static  int computeSampleSize(BitmapFactory.Options options,

 62             int minSideLength, int maxNumOfPixels) {

 63         int initialSize = computeInitialSampleSize(options, minSideLength,

 64                 maxNumOfPixels);

 65 

 66         int roundedSize;

 67         if (initialSize <= 8) {

 68             roundedSize = 1;

 69             while (roundedSize < initialSize) {

 70                 roundedSize <<= 1;

 71             }

 72         } else {

 73             roundedSize = (initialSize + 7) / 8 * 8;

 74         }

 75 

 76         return roundedSize;

 77     }

 78 

 79     /**

 80      * compute Initial Sample Size

 81      * 

 82      * @param options

 83      * @param minSideLength

 84      * @param maxNumOfPixels

 85      * @return

 86      */

 87     private static  int computeInitialSampleSize(BitmapFactory.Options options,

 88             int minSideLength, int maxNumOfPixels) {

 89         double w = options.outWidth;

 90         double h = options.outHeight;

 91 

 92         // 上下限范围

 93         int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math

 94                 .sqrt(w * h / maxNumOfPixels));

 95         int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(

 96                 Math.floor(w / minSideLength), Math.floor(h / minSideLength));

 97 

 98         if (upperBound < lowerBound) {

 99             // return the larger one when there is no overlapping zone.

100             return lowerBound;

101         }

102 

103         if ((maxNumOfPixels == -1) && (minSideLength == -1)) {

104             return 1;

105         } else if (minSideLength == -1) {

106             return lowerBound;

107         } else {

108             return upperBound;

109         }

110     }

111 }