android 图片压缩工具类

package com.wanng.xxx.mobile; 
import java.io.BufferedOutputStream; 
import java.io.ByteArrayOutputStream; 
import java.io.File; 
import java.io.FileOutputStream; 
import java.io.IOException; 
 
 
import android.content.Context; 
import android.content.Intent; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.net.Uri; 
import android.os.Environment; 
import android.util.Log; 
 
/**  
 * @author BigWanng  
 * @version 2013-6-6 下午1:55:33  
 * TODO 处理图片压缩的工具类 
 */ 
public class PictureUtils { 
	private final static int compressVal=75; 
	/** 
	  * 把bitmap转换成String 
	  * 将图片保存到本地 
	  * @param filePath 
	  * @return 
	  */ 
	 public static String bitmapToString(Bitmap bitmap) { 
		   ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
		   bitmap.compress(Bitmap.CompressFormat.JPEG, compressVal, baos); 
		    
		   byte[] b = baos.toByteArray(); 
		   return Base64.encodeToString(b, Base64.DEFAULT); 
		 } 
	 
	 /** 
	  * 计算图片的缩放值 
	  * 如果图片的原始高度或者宽度大与我们期望的宽度和高度，我们需要计算出缩放比例的数值。否则就不缩放。 
	  * heightRatio是图片原始高度与压缩后高度的倍数， 
	  * widthRatio是图片原始宽度与压缩后宽度的倍数。 
	  * inSampleSize就是缩放值 ，取heightRatio与widthRatio中最小的值。 
	  * inSampleSize为1表示宽度和高度不缩放，为2表示压缩后的宽度与高度为原来的1/2(图片为原1/4)。 
	  * @param options 
	  * @param reqWidth 
	  * @param reqHeight 
	  * @return 
	  */ 
	 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) { 
	 
	     // Calculate ratios of height and width to requested height and width  
	     final int heightRatio = Math.round((float) height / (float) reqHeight); 
	     final int widthRatio = Math.round((float) width / (float) reqWidth); 
	 
	     // Choose the smallest ratio as inSampleSize value, this will guarantee 
	     // a final image with both dimensions(尺寸) larger than or equal to the requested height and width. 
	     inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio; 
	   } 
	 
	   return inSampleSize; 
	 } 
	 
	 /** 
	  * 根据路径获得图片并压缩返回bitmap用于显示 
	  *  
	  * @param imagesrc 
	  * @return 
	  */ 
	 public static Bitmap getSmallBitmap(String filePath,int w,int h) { 
		   final BitmapFactory.Options options = new BitmapFactory.Options(); 
		    
		   //该值设为true那么将不返回实际的bitmap不给其分配内存空间而里面只包括一些解码边界信息即图片大小信息 
		   options.inJustDecodeBounds = true;//inJustDecodeBounds设置为true，可以不把图片读到内存中,但依然可以计算出图片的大小 
		   BitmapFactory.decodeFile(filePath, options); 
		 
		   // Calculate inSampleSize 
		   options.inSampleSize = calculateInSampleSize(options, w, h); 
		 
		   // Decode bitmap with inSampleSize set 
		   options.inJustDecodeBounds = false;//重新读入图片，注意这次要把options.inJustDecodeBounds 设为 false 
		   Bitmap bitmap = BitmapFactory.decodeFile(filePath, options);// BitmapFactory.decodeFile()按指定大小取得图片缩略图 
		    
		   return bitmap; 
		 } 
	 
	 /** 
	  * 保存到本地 
	  * @param bitmap 
	  */ 
	 public static void saveBitmap(Bitmap bitmap,String savePath){ 
			ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
			File file = new File(savePath); 
			try { 
				file.createNewFile(); 
				BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream(file)); 
 
				bitmap.compress(Bitmap.CompressFormat.JPEG, compressVal, baos); 
				os.write(baos.toByteArray()); 
 
				os.flush(); 
				os.close(); 
				 
			} catch (IOException e) { 
				Log.d("BITMAP", e.getMessage()); 
			} finally { 
				if (bitmap != null) { 
					bitmap.recycle(); 
				} 
			}  
		 } 
	  
	 /*** 
	 * 根据路径删除图片 
     * @param path 
     * @return 
     * @throws IOException 
     */ 
    public static boolean deleteTempFile(String path)throws IOException{ 
        boolean isOk=true; 
        File file = new File(path); 
        if(file!=null){ 
            if(file.exists()){ 
                if(!file.delete()){ 
                    isOk=false; 
                } 
            } 
        } 
        return isOk; 
    } 
     
    /*** 
     * 获取文件扩展名 
     * @param filename 
     * @return 返回文件扩展名 
     */ 
    public static String getExtensionName(String filename) { 
        if ((filename != null) && (filename.length() > 0)) { 
            int dot = filename.lastIndexOf('.'); 
            if ((dot >-1) && (dot < (filename.length() - 1))) { 
                return filename.substring(dot + 1); 
            } 
        } 
        return filename; 
    } 
     
 
}