Android 实现4MB以上大图片压缩不失真方法

import java.io.ByteArrayOutputStream;
import java.io.File;

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.Base64;

public class PictureUtil {

/**
* 把bitmap转换成String
*
* @param filePath
* @return
*/
public static String bitmapToString(String filePath) {
Bitmap bm = getSmallBitmap(filePath);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.JPEG, 40, baos);
byte[] b = baos.toByteArray();
int x = b.length;
System.out.println("" + x);
return Base64.encodeToString(b, Base64.DEFAULT);

}

/**
* 计算图片的缩放值
*
* @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 larger than or equal to the
// requested height and width.
inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
}

return inSampleSize;
}

/**
* 根据路径获得突破并压缩返回bitmap用于显示
*
* @param imagesrc
* @return
*/
public static Bitmap getSmallBitmap(String filePath) {
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(filePath, options);

// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, 480, 800);

// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;

return BitmapFactory.decodeFile(filePath, options);
}

/**
* 根据路径删除图片
*
* @param path
*/
public static void deleteTempFile(String path) {
File file = new File(path);
if (file.exists()) {
file.delete();
}
}

/**
* 添加到图库
*/
public static void galleryAddPic(Context context, String path) {
Intent mediaScanIntent = new Intent(
Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
File f = new File(path);
Uri contentUri = Uri.fromFile(f);
mediaScanIntent.setData(contentUri);
context.sendBroadcast(mediaScanIntent);
}

/**
* 获取保存图片的目录
*
* @return
*/
public static File getAlbumDir() {
File dir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
getAlbumName());
if (!dir.exists()) {
dir.mkdirs();
}
return dir;
}

/**
* 获取保存 隐患检查的图片文件夹名称
*
* @return
*/
public static String getAlbumName() {
return "sheguantong";
}
}