android bitmap compress（图片压缩）

android bitmap compress

android的照相功能随着手机硬件的发展，变得越来越强大，能够找出很高分辨率的图片。

有些场景中，需要照相并且上传到服务，但是由于图片的大小太大，那么就上传就会很慢(在有些网络情况下)，而且很耗流量，要想速度快，那么就需要减小图片的大小。减少图片的大小有两种方法，1. 照小图片； 2. 压缩大图片。 照相时获取小图片一般不太符合要求，因为，图片的清晰度会很差，但是这种情况有个好处就是应用速度会快些； 压缩图片，就是把大图片压缩小，降低图片的质量，在一定范围内，降低图片的大小，并且满足需求（图片仍就清晰）。下面组要是介绍图片的压缩：

1. 照相请查看http://blog.csdn.net/luhuajcdd/article/details/8826587 ->想要保存图片到制定目录，启动Camera应用时，需要指定文件

2. 压缩过程：

    2.1 从图片路径中读取图片(图片很大，不能全部加在到内存中处理，要是全部加载到内存中会内存溢出)

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1. final BitmapFactory.Options options =new BitmapFactory.Options(); 
2.     options.inJustDecodeBounds = true; 
3.     BitmapFactory.decodeFile(filePath, options); 
4.  
5.     // Calculate inSampleSize 
6.     options.inSampleSize = calculateInSampleSize(options, 480, 800); 
7.  
8.     // Decode bitmap with inSampleSize set 
9.     options.inJustDecodeBounds = false; 
10.      
11.     Bitmap bm = BitmapFactory.decodeFile(filePath, options); 

 final BitmapFactory.Options options = new BitmapFactory.Options();options.inJustDecodeBounds = true;BitmapFactory.decodeFile(filePath, options);// Calculate inSampleSizeoptions.inSampleSize = calculateInSampleSize(options, 480, 800);// Decode bitmap with inSampleSize setoptions.inJustDecodeBounds = false;Bitmap bm = BitmapFactory.decodeFile(filePath, options);

    2.2 处理图片旋转  

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1. int degree = readPictureDegree(filePath); 
2.         bm = rotateBitmap(bm,degree) ; 

int degree = readPictureDegree(filePath);bm = rotateBitmap(bm,degree) ;

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1. private staticint readPictureDegree(String path) {   
2.            int degree  = 0;   
3.            try {   
4.                    ExifInterface exifInterface = new ExifInterface(path);   
5.                    int orientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);   
6.                    switch (orientation) {   
7.                    case ExifInterface.ORIENTATION_ROTATE_90:   
8.                            degree = 90;   
9.                            break;   
10.                    case ExifInterface.ORIENTATION_ROTATE_180:   
11.                            degree = 180;   
12.                            break;   
13.                    case ExifInterface.ORIENTATION_ROTATE_270:   
14.                            degree = 270;   
15.                            break;   
16.                    }   
17.            } catch (IOException e) {   
18.                    e.printStackTrace();   
19.            }   
20.            return degree;   
21.        }  

private static int readPictureDegree(String path) {         int degree  = 0;         try {                 ExifInterface exifInterface = new ExifInterface(path);                 int orientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);                 switch (orientation) {                 case ExifInterface.ORIENTATION_ROTATE_90:                         degree = 90;                         break;                 case ExifInterface.ORIENTATION_ROTATE_180:                         degree = 180;                         break;                 case ExifInterface.ORIENTATION_ROTATE_270:                         degree = 270;                         break;                 }         } catch (IOException e) {                 e.printStackTrace();         }         return degree;     } 

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1. private static Bitmap rotateBitmap(Bitmap bitmap,int rotate){ 
2.         if(bitmap == null) 
3.             return null ; 
4.          
5.         int w = bitmap.getWidth(); 
6.         int h = bitmap.getHeight(); 
7.  
8.         // Setting post rotate to 90 
9.         Matrix mtx = new Matrix(); 
10.         mtx.postRotate(rotate); 
11.         return Bitmap.createBitmap(bitmap,0, 0, w, h, mtx,true); 
12.     } 

private static Bitmap rotateBitmap(Bitmap bitmap, int rotate){if(bitmap == null)return null ;int w = bitmap.getWidth();int h = bitmap.getHeight();// Setting post rotate to 90Matrix mtx = new Matrix();mtx.postRotate(rotate);return Bitmap.createBitmap(bitmap, 0, 0, w, h, mtx, true);}

    2.3压缩图片       

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1. bm.compress(Bitmap.CompressFormat.JPEG, 30, baos);//30 是压缩率，表示压缩70%; 如果不压缩是100，表示压缩率为0 

bm.compress(Bitmap.CompressFormat.JPEG, 30, baos);//30 是压缩率，表示压缩70%; 如果不压缩是100，表示压缩率为0

完整的方法代码：

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1. public static Bitmap getSmallBitmap(String filePath) { 
2.              
3.         final BitmapFactory.Options options =new BitmapFactory.Options(); 
4.         options.inJustDecodeBounds = true; 
5.         BitmapFactory.decodeFile(filePath, options); 
6.  
7.         // Calculate inSampleSize 
8.         options.inSampleSize = calculateInSampleSize(options, 480, 800); 
9.  
10.         // Decode bitmap with inSampleSize set 
11.         options.inJustDecodeBounds = false; 
12.          
13.         Bitmap bm = BitmapFactory.decodeFile(filePath, options); 
14.         if(bm == null){ 
15.             return  null; 
16.         } 
17.         int degree = readPictureDegree(filePath); 
18.         bm = rotateBitmap(bm,degree) ; 
19.         ByteArrayOutputStream baos = null ; 
20.         try{ 
21.             baos = new ByteArrayOutputStream(); 
22.             bm.compress(Bitmap.CompressFormat.JPEG, 30, baos); 
23.              
24.         }finally{ 
25.             try { 
26.                 if(baos != null) 
27.                     baos.close() ; 
28.             } catch (IOException e) { 
29.                 e.printStackTrace(); 
30.             } 
31.         } 
32.         return bm ; 
33.  
34.     } 

public static Bitmap getSmallBitmap(String filePath) {    final BitmapFactory.Options options = new BitmapFactory.Options();options.inJustDecodeBounds = true;BitmapFactory.decodeFile(filePath, options);// Calculate inSampleSizeoptions.inSampleSize = calculateInSampleSize(options, 480, 800);// Decode bitmap with inSampleSize setoptions.inJustDecodeBounds = false;Bitmap bm = BitmapFactory.decodeFile(filePath, options);if(bm == null){return  null;}int degree = readPictureDegree(filePath);bm = rotateBitmap(bm,degree) ;ByteArrayOutputStream baos = null ;try{baos = new ByteArrayOutputStream();bm.compress(Bitmap.CompressFormat.JPEG, 30, baos);}finally{try {if(baos != null)baos.close() ;} catch (IOException e) {e.printStackTrace();}}return bm ;}

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1. private staticint calculateInSampleSize(BitmapFactory.Options options, 
2.             int reqWidth, int reqHeight) { 
3.         // Raw height and width of image 
4.         final int height = options.outHeight; 
5.         final int width = options.outWidth; 
6.         int inSampleSize = 1; 
7.  
8.         if (height > reqHeight || width > reqWidth) { 
9.  
10.             // Calculate ratios of height and width to requested height and 
11.             // width 
12.             final int heightRatio = Math.round((float) height 
13.                     / (float) reqHeight); 
14.             final int widthRatio = Math.round((float) width / (float) reqWidth); 
15.  
16.             // Choose the smallest ratio as inSampleSize value, this will 
17.             // guarantee 
18.             // a final image with both dimensions larger than or equal to the 
19.             // requested height and width. 
20.             inSampleSize = heightRatio < widthRatio ? widthRatio : heightRatio; 
21.         } 
22.  
23.         return inSampleSize; 
24.     } 

private static int calculateInSampleSize(BitmapFactory.Options options,int reqWidth, int reqHeight) {// Raw height and width of imagefinal 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// widthfinal 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 ? widthRatio : heightRatio;}return inSampleSize;}

转自：http://blog.csdn.net/luhuajcdd/article/details/8948261