位图的尺寸意图通过返回的相机？ [英] Size of bitmap returned by camera via intent?

问题描述

我如何得到一个位图从相机一定（内存型）大小？

How do I get a bitmap with a certain (memory friendly) size from the camera?

我开始用相机意图：

Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE); 
cameraIntent.putExtra("return-data", true);

photoUri = Uri.fromFile(new File(Environment.getExternalStorageDirectory(), "mytmpimg.jpg"));
cameraIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, photoUri);        

startActivityForResult(cameraIntent, REQUEST_CODE_CAMERA);

我在这里处理结果是：

I handle the result here:

//  Bitmap photo = (Bitmap) intent.getExtras().get("data");

Bitmap photo = getBitmap(photoUri);

现在，如果我使用注释行 - 直接将位图，我总是得到一个160×120位，这是太小了。如果我使用一些标准的东西，我发现（方法getBitmap）从URI加载它，它加载一个2560 X 1920的位图（！），并消耗将近20 MB的内存。

Now if I use the commented line - get the bitmap directly, I get always a 160 x 120 bitmap, and that's too small. If I load it from the URI using some standard stuff I found (method getBitmap), it loads a 2560 x 1920 bitmap (!) and that consumes almost 20 mb memory.

如何加载比方说480 * 800（同样大小的相机preVIEW显示我）？

How do I load let's say 480 x 800 (the same size the camera preview shows me)?

而无需将2560 X 1920加载到内存中，并缩小。

Without having to load the 2560 x 1920 into memory and scaling down.

推荐答案

下面是我想出的基础上，从中旧Android版本删除了作物库调用getBitmap（）方法。我做了一些修改：

Here is what I came up with, based on a method called getBitmap() from a crop library which was removed from old Android version. I did some modifications:

private Bitmap getBitmap(Uri uri, int width, int height) {
    InputStream in = null;
    try {
        int IMAGE_MAX_SIZE = Math.max(width, height);
        in = getContentResolver().openInputStream(uri);

        //Decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;

        BitmapFactory.decodeStream(in, null, o);
        in.close();

        int scale = 1;
        if (o.outHeight > IMAGE_MAX_SIZE || o.outWidth > IMAGE_MAX_SIZE) {
            scale = (int)Math.pow(2, (int) Math.round(Math.log(IMAGE_MAX_SIZE / (double) Math.max(o.outHeight, o.outWidth)) / Math.log(0.5)));
        }

        //adjust sample size such that the image is bigger than the result
        scale -= 1;

        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        in = getContentResolver().openInputStream(uri);
        Bitmap b = BitmapFactory.decodeStream(in, null, o2);
        in.close();

        //scale bitmap to desired size
        Bitmap scaledBitmap = Bitmap.createScaledBitmap(b, width, height, false);

        //free memory
        b.recycle();

        return scaledBitmap;

    } catch (FileNotFoundException e) {
    } catch (IOException e) {
    }
    return null;
}

这样做是加载使用BitmapFactory.Options（）位图+一些样本量 - 这样原始图像不会加载到内存中。问题是，样本大小只是工作在步骤。而为了得到这将产生最小样本量中减去1 - 我使用一些数学我复制获得最小样本规模为我的形象。比位图的大小，我需要更大的。

What this does is load the bitmap using BitmapFactory.Options() + some sample size - this way the original image is not loaded into memory. The problem is that the sample size just works in steps. I get the "min" sample size for my image using some maths I copied - and subtract 1 in order to get the sample size which will produce the min. bitmap bigger than the size I need.

和则为了准确地与要求的尺寸得到位图做 Bitmap.createScaledBitmap（B，宽度，高度，FALSE）正常比例; 。之后立刻就回收了更大的位图。这是很重要的，因为，例如，在我的情况下，为了获得480 x 800的位图，更大的位图是1280 * 960，并占用4.6MB内存。

And then in order to get the bitmap with exactly the size requested do normal scaling with Bitmap.createScaledBitmap(b, width, height, false);. And immediatly after it recycle the bigger bitmap. This is important, because, for example, in my case, in order to get 480 x 800 bitmap, the bigger bitmap was 1280 x 960 and that occupies 4.6mb memory.

一个更多的内存友好的方式将不能调整比例，所以较小的位图将被调整以匹配所需的大小。但是，这将降低图像的质量。

A more memory friendly way would be to not adjust scale, so a smaller bitmap will be scaled up to match the required size. But this will reduce the quality of the image.

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