BitmapFactory.de codeStream返回null，则选项被设置 [英] BitmapFactory.decodeStream returning null when options are set

问题描述

我在使用 BitmapFactory.de codeStream（InputStream的）问题。使用时不带选项，它会返回一个图像。但是，当我使用它的选项， .DE codeStream（的InputStream，空，选项）它永远不会返回位图。

我想要做的就是下采样位图之前，我其实加载它以节省内存。 我读过一些好的导游，但没有使用 .DE codeStream 。

• <一个href="http://groups.google.com/group/android-developers/browse_thread/thread/1e9d19c3adf1a768/afef1c8341a63ad2?lnk=gst&q=samuh#afef1c8341a63ad2">Handling大位图 的

• 这里

在Android的 <

• 图像处理/ EM>

工作得很好

 网​​址URL =新的URL（SURL）;
HttpURLConnection的连接=（HttpURLConnection类）url.openConnection（）;

InputStream的是= connection.getInputStream（）;
位图IMG = BitmapFactory.de codeStream（是，空，期权）;
 

不工作

 的InputStream是= connection.getInputStream（）;
位图IMG = BitmapFactory.de codeStream（是，空，期权）;

InputStream的是= connection.getInputStream（）;

选项​​选项=新BitmapFactory.Options（）;
options.inJustDe codeBounds = TRUE;

BitmapFactory.de codeStream（是，空，期权）;

布尔scaleByHeight = Math.abs（options.outHeight  -  TARGET_HEIGHT）＆GT; = Math.abs（options.outWidth  -  TARGET_WIDTH）;

如果（options.outHeight * options.outWidth * 2  - ; = 200 * 100 * 2）{
    //加载，扩展到2个最小的功率会得到它＆LT; =所需的尺寸
    双采样大小= scaleByHeight
    ？ options.outHeight / TARGET_HEIGHT
    ：options.outWidth / TARGET_WIDTH;
    options.inSampleSize =
        （INT）Math.pow（2D，Math.floor（
        将Math.log（采样大小）/Math.log（2D）））;
}

//做实际的解码
options.inJustDe codeBounds = FALSE;
位图IMG = BitmapFactory.de codeStream（是，空，期权）;
 

解决方案

但问题是，一旦你使用一个InputStream从HttpURLConnection类来获取图像元数据，你不能倒退，并再次使用相同的InputStream。

因此​​，你必须创建一个新的InputStream为图像的实际采样。

 选项选项=新BitmapFactory.Options（）;
  options.inJustDe codeBounds = TRUE;

  BitmapFactory.de codeStream（是，空，期权）;

  布尔scaleByHeight = Math.abs（options.outHeight  -  TARGET_HEIGHT）＆GT; = Math.abs（options.outWidth  -  TARGET_WIDTH）;

  如果（options.outHeight * options.outWidth * 2  - ; = 200 * 200 * 2）{
         //加载，扩展到2个最小的功率会得到它＆LT; =所需的尺寸
        双采样大小= scaleByHeight
              ？ options.outHeight / TARGET_HEIGHT
              ：options.outWidth / TARGET_WIDTH;
        options.inSampleSize =
              （INT）Math.pow（2D，Math.floor（
              将Math.log（采样大小）/Math.log（2D）））;
     }

        //做实际的解码
        options.inJustDe codeBounds = FALSE;

        is.close（）;
        是= getHTTPConnectionInputStream（SURL）;
        位图IMG = BitmapFactory.de codeStream（是，空，期权）;
        is.close（）;
 

I'm having issues with BitmapFactory.decodeStream(inputStream). When using it without options, it will return an image. But when I use it with options as in .decodeStream(inputStream, null, options) it never returns Bitmaps.

What I'm trying to do is to downsample a Bitmap before I actually load it to save memory. I've read some good guides, but none using .decodeStream.

• Handling large Bitmaps

• And here

• Image Processing in Android

WORKS JUST FINE

URL url = new URL(sUrl);
HttpURLConnection connection  = (HttpURLConnection) url.openConnection();

InputStream is = connection.getInputStream();
Bitmap img = BitmapFactory.decodeStream(is, null, options);

DOESN'T WORK

InputStream is = connection.getInputStream();
Bitmap img = BitmapFactory.decodeStream(is, null, options);

InputStream is = connection.getInputStream();

Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;

BitmapFactory.decodeStream(is, null, options);

Boolean scaleByHeight = Math.abs(options.outHeight - TARGET_HEIGHT) >= Math.abs(options.outWidth - TARGET_WIDTH);

if (options.outHeight * options.outWidth * 2 >= 200*100*2){
    // Load, scaling to smallest power of 2 that'll get it <= desired dimensions
    double sampleSize = scaleByHeight
    ? options.outHeight / TARGET_HEIGHT
    : options.outWidth / TARGET_WIDTH;
    options.inSampleSize =
        (int)Math.pow(2d, Math.floor(
        Math.log(sampleSize)/Math.log(2d)));
}

// Do the actual decoding
options.inJustDecodeBounds = false;
Bitmap img = BitmapFactory.decodeStream(is, null, options);

解决方案

The problem was that once you've used an InputStream from a HttpUrlConnection to fetch image metadata, you can't rewind and use the same InputStream again.

Therefore you have to create a new InputStream for the actual sampling of the image.

  Options options = new BitmapFactory.Options();
  options.inJustDecodeBounds = true;

  BitmapFactory.decodeStream(is, null, options);

  Boolean scaleByHeight = Math.abs(options.outHeight - TARGET_HEIGHT) >= Math.abs(options.outWidth - TARGET_WIDTH);

  if(options.outHeight * options.outWidth * 2 >= 200*200*2){
         // Load, scaling to smallest power of 2 that'll get it <= desired dimensions
        double sampleSize = scaleByHeight
              ? options.outHeight / TARGET_HEIGHT
              : options.outWidth / TARGET_WIDTH;
        options.inSampleSize = 
              (int)Math.pow(2d, Math.floor(
              Math.log(sampleSize)/Math.log(2d)));
     }

        // Do the actual decoding
        options.inJustDecodeBounds = false;

        is.close();
        is = getHTTPConnectionInputStream(sUrl);
        Bitmap img = BitmapFactory.decodeStream(is, null, options);
        is.close();

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