Question

我想将URL转换为Bitmap image.i我也尝试在SD卡上压缩并保存这个位图，但是当我运行代码时，Web Image-view中没有显示任何图像。我有以下代码：

Logger.d(LOG_TAG, "Enter retrieveImageData()");
    URL url = new URL(imageUrl);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setReadTimeout(CONNECTTION_TIMEOUT);
    // determine the image size and allocate a buffer
    int fileSize = connection.getContentLength();
    if (fileSize < 0) {
        Logger.d(LOG_TAG, "retrieveImageData()->file size less than 0");
        return null;
    }
    byte[] imageData = null;

    byte[] buffer = new byte[BUFFER_SIZE];

    // download the file
    // if(Global.show_logs) Log.d(LOG_TAG, "fetching image " + imageUrl +
    // " (" + fileSize + ")");
    BufferedInputStream istream = new BufferedInputStream(connection.getInputStream());

    if ((!(height == -1)) && (!(width == -1))) {
        Logger.d(LOG_TAG, "Enter retrieveImageData() :width="+width+" height"+height);
        File tmpFile = GlobalFunctions.getTmpFile();

        if (tmpFile == null)
            throw new IOException("DroidFu::ImageLoader: Could not create temp file!");

        BufferedOutputStream ostream = new BufferedOutputStream(new FileOutputStream(tmpFile));

        Logger.d(LOG_TAG, "before call of IOUtils.copy");
        IOUtils.copy(istream, ostream);
        Logger.d(LOG_TAG, "after call of IOUtils.copy");
        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(tmpFile.getAbsolutePath(), options);

        // Calculate inSampleSize
        Logger.d(LOG_TAG, "before call of calculateInSampleSize()");
        options.inSampleSize = calculateInSampleSize(options, width, height);
        Logger.d(LOG_TAG, "after call of calculateInSampleSize()");

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        Logger.d(LOG_TAG, "Absolute path of tmp file is: "+tmpFile.getAbsolutePath());
        Bitmap b=BitmapFactory.decodeFile(tmpFile.getAbsolutePath(), options);
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        b.compress(Bitmap.CompressFormat.PNG, 100, stream);

        byte[] byteArray = stream.toByteArray();

        b.recycle();
        //imageData = stream.toByteArray();

        istream.close();
        ostream.close();
        stream.close();
        Logger.d(LOG_TAG, "Exit retrieveImageData() after resizing to imageview");
        return byteArray;
    }

但是这个代码在这一行抛出异常（Throwable e），而且“e”也是null：

b.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

Answer 1

试试这个。

将位图转换为字节数组： -

Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
bmp.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

将字节数组转换为位图图像： -

Bitmap bmp = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);

Answer 2

将位图转换为字节数组，您可以使用

        final int lnth=bitmap.getByteCount();

        ByteBuffer dst= ByteBuffer.allocate(lnth);
        bitmap.copyPixelsToBuffer( dst);
        byte[] barray=dst.array();

从字节数组中获取位图

Bitmap bitmap = new BitmapFactory().decodeByteArray(byte_array, 0/* starting index*/, byte_array.length/*no of byte to read*/)

Answer 3

以下是更高级image Loader library

的链接

用法如下：

首先将此代码放入您的主要活动中。

DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder().showStubImage(R.drawable.ic_stub).showImageOnFail(R.drawable.ic_error).showImageForEmptyUri(R.drawable.ic_empty_url).cacheInMemory().cacheOnDisc().build();
    // Create global configuration and initialize ImageLoader with this
    // configuration
    ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(getApplicationContext()).defaultDisplayImageOptions(defaultOptions).build();
    ImageLoader.getInstance().init(config);

然后在你的班级中使用它：

private ImageLoader imageLoader;

在你的onCreate（）方法中

imageLoader = ImageLoader.getInstance();

然后像这样加载图片

imageLoader.displayImage(IMG_URL, imageView);

如何将位图转换为字节数组

3 个答案: