Bitmap使用

/**
     * 由本地文件路径、网络url或者项目的资源文件，生成Bitmap（旧，极端情况下可能造成OOM）
     * @param filePath
     */
    private void productBitmap(String filePath){
        Bitmap des_bitmap = null;
        BitmapFactory.Options options  = new BitmapFactory.Options();

        //本地文件路径或者网络url
        Uri uri = Uri.parse(filePath);
        des_bitmap = BitmapFactory.decodeFile(uri.toString(),options);

        //项目资源文件
        des_bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.ic_launcher);

        if(iv_bitmap_test!=null) {
            iv_bitmap_test.setImageBitmap(des_bitmap);
        }else{
            iv_bitmap_test = (ImageView) findViewById(R.id.iv_bitmap_test);
            iv_bitmap_test.setImageBitmap(des_bitmap);
        }
    }

/**
     * 由File转成长宽固定相同比例的bitmap。实现长宽等比例缩放
     * @return
     */
    private Bitmap resizeBitmap(String filePath){
        Bitmap des_bitmap ;

        BitmapFactory.Options options = new BitmapFactory.Options();
        //表示缩略图大小为原始图片大小的几分之一，即如果这个值为2，则取出的缩略图的宽和高都是原始图片的1/2，图片大小就为原始大小的1/4
        options.inJustDecodeBounds = true;
        des_bitmap = BitmapFactory.decodeFile(filePath,options);//des_bitmap为null.因为options.inJustDecodeBounds = true，节省内存

        //长宽按照相同比例缩放
        int height = options.outHeight;
        int width = options.outWidth;
        int scale;//缩放值，因为为等比例缩放.
        if(height > width){//以高为准
            scale = (int) (height/200.0f);//该200说明目标大小为200PX
        }else{
            scale = (int) (width/200.0f);//该200说明目标大小为200PX
        }
        if(scale<=0){
            scale = 1;
        }
        options.inSampleSize = scale;
        options.inJustDecodeBounds = false;
        Bitmap new_bitmap = BitmapFactory.decodeFile(filePath,options);//des_bitmap不为null
        if(des_bitmap!=new_bitmap){
            des_bitmap.recycle();//注意销毁不用的bitmap
        }
        return new_bitmap;
    }

/**
     * 由Bitmap转成指定大小的Bitmap，实现缩放成指定准确大小Bitmap
     * @param filePath
     * @param sWidth 目标宽
     * @param sHeight 目标高
     */
    private Bitmap resizeBitmap(String filePath,int sWidth,int sHeight){
        //缩放到指定的长宽
        Bitmap mBitmap;
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = false;
        mBitmap = BitmapFactory.decodeFile(filePath,options);
        if(mBitmap == null){
            return null;
        }
        int bmpWidth = mBitmap.getWidth();
        int bmpHeight = mBitmap.getHeight();
        // 缩放图片的尺寸
        float scaleWidth = (float) sWidth / bmpWidth; // 按固定大小缩放 sWidth 写多大就多大
        float scaleHeight = (float) sHeight / bmpHeight; //
        Matrix matrix = new Matrix();

　　　　//matrix.postScale(1, -1); //镜像垂直翻转
　　　　//matrix.postScale(-1, 1); //镜像水平翻转
　　　　//matrix.postRotate(-90); //旋转-90度

matrix.postScale(scaleWidth, scaleHeight);// 产生缩放后的Bitmap对象 Bitmap resizeBitmap = Bitmap.createBitmap(mBitmap, 0, 0, bmpWidth, bmpHeight, matrix, false); mBitmap.recycle(); return resizeBitmap; }

/**
     * 保存内存中的bitmap到本地文件
     * @param bitmap 要保存的bitmap
     * @param localPath 保存在本地的文件名,绝对路径
     * */
    public static void saveBitmap2File(Bitmap bitmap,String localPath){
        if (bitmap == null) {
            return;
        }
        try {
            File file = new File(localPath);
            FileOutputStream fos = new FileOutputStream(file);
            assert bitmap != null;
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
            fos.flush();
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

/**
     * 由本地文件生成bitmap时，节省内存的方法
     * @param context
     * @param filePath
     * @throws Exception
     */
    private void productBitmap(Context context,String filePath) throws Exception {
        Bitmap des_bitmap = null;
        BitmapFactory.Options options = new BitmapFactory.Options();

        //方法一.本地文件路径
        File file = new File(filePath);
        try {
            FileInputStream is = new FileInputStream(file);
            FileDescriptor fd = is.getFD();
            des_bitmap = BitmapFactory.decodeFileDescriptor(fd,null,options);
            if(iv_bitmap_test!=null) {
                iv_bitmap_test.setImageBitmap(des_bitmap);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }


        //方法二。
        //不允许网络url，只允许本地绝对路径即file://sdcard//开头
//        String url = "http://itfish.net/Home/Modules/Images/itfish_54346_0.jpg";
//        String url = Environment
//                .getExternalStorageDirectory().getAbsolutePath()
//                + File.separator+"fitmix"+File.separator+"Cover"+File.separator+"137_radio.jpg";
        String url = "file:///sdcard/"+"fitmix"+File.separator+"Cover"+File.separator+"137_radio.jpg";//注意路径
        ParcelFileDescriptor parcelFileDescriptor = context.getContentResolver().openFileDescriptor(Uri.parse(url),"r");
        FileDescriptor fileDescriptor ;
        if(parcelFileDescriptor != null){
            fileDescriptor = parcelFileDescriptor.getFileDescriptor();
        }else{
            fileDescriptor = null;
        }

        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFileDescriptor(fileDescriptor, null, options);

        int inSampleSize = 1;

        if (options.outHeight > 200.0f || options.outWidth > 200.0f) {
            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width lower or equal to the requested height and width.
            while ((options.outHeight / inSampleSize) > 200.0f || (options.outWidth / inSampleSize) > 200.0f) {
                inSampleSize *= 2;
            }
        }

        options.inSampleSize = inSampleSize;
        options.inJustDecodeBounds = false;

        Bitmap decodeSampledBitmap = BitmapFactory.decodeFileDescriptor(fileDescriptor, null, options);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            parcelFileDescriptor.close();
        }

        iv_bitmap_test.setImageBitmap(decodeSampledBitmap);
    }