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 }

 

posted @ 2013-09-27 23:04  skyko  阅读(504)  评论(0)    收藏  举报