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android bitmap compress(圖片壓縮)代碼

更新時(shí)間：2013年06月03日 11:05:19 作者：

android bitmap compress(圖片壓縮)代碼，需要的朋友可以參考一下

android的照相功能隨著手機(jī)硬件的發(fā)展，變得越來(lái)越強(qiáng)大，能夠找出很高分辨率的圖片。
有些場(chǎng)景中，需要照相并且上傳到服務(wù)，但是由于圖片的大小太大，那么就上傳就會(huì)很慢(在有些網(wǎng)絡(luò)情況下)，而且很耗流量，要想速度快，那么就需要減小圖片的大小。減少圖片的大小有兩種方法，1. 照小圖片； 2. 壓縮大圖片。照相時(shí)獲取小圖片一般不太符合要求，因?yàn)?，圖片的清晰度會(huì)很差，但是這種情況有個(gè)好處就是應(yīng)用速度會(huì)快些；壓縮圖片，就是把大圖片壓縮小，降低圖片的質(zhì)量，在一定范圍內(nèi)，降低圖片的大小，并且滿足需求（圖片仍就清晰）。下面組要是介紹圖片的壓縮：

1. 照相請(qǐng)查看http://www.dbjr.com.cn/article/37760.htm ->想要保存圖片到制定目錄，啟動(dòng)Camera應(yīng)用時(shí)，需要指定文件
2. 壓縮過(guò)程：
2.1 從圖片路徑中讀取圖片(圖片很大，不能全部加在到內(nèi)存中處理，要是全部加載到內(nèi)存中會(huì)內(nèi)存溢出)
[java]

復(fù)制代碼代碼如下:

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;

    Bitmap bm = BitmapFactory.decodeFile(filePath, options);

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;

Bitmap bm = BitmapFactory.decodeFile(filePath, options);

2.2 處理圖片旋轉(zhuǎn)
[java]

復(fù)制代碼代碼如下:

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

int degree = readPictureDegree(filePath);
bm = rotateBitmap(bm,degree) ;[java] view plaincopyprint?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;
       }

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;
    }

[java]

復(fù)制代碼代碼如下:

view plaincopyprint?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 90
        Matrix mtx = new Matrix();
        mtx.postRotate(rotate);
        return Bitmap.createBitmap(bitmap, 0, 0, w, h, mtx, true);
    }

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 90
Matrix mtx = new Matrix();
mtx.postRotate(rotate);
return Bitmap.createBitmap(bitmap, 0, 0, w, h, mtx, true);
}

2.3壓縮圖片
[java]

復(fù)制代碼代碼如下:

bm.compress(Bitmap.CompressFormat.JPEG, 30, baos);//30 是壓縮率，表示壓縮70%; 如果不壓縮是100，表示壓縮率為0

完整的方法代碼：
[java]

復(fù)制代碼代碼如下:

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;

        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 ;

    }

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;

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 ;

}

[java]

復(fù)制代碼代碼如下:

view plaincopyprint?private 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 ? widthRatio : heightRatio;
        }

        return inSampleSize;
    }

private 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 ? widthRatio : heightRatio;
}

return inSampleSize;
}

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