Question

如何使用给定的URI从SD卡获取缩略图？我已经尝试过使用bitmapfactory，但性能不好或者OutOfMemoryError 我将使用大量数据将缩略图放到列表视图中我应该使用缩略图还是任何建议？如果要使用缩略图，那么该怎么做......？

提前感谢您的帮助

Answer 1

 // Parameters
 int w,h;     

 // First only decode image size
 BitmapFactory.Options opt = new BitmapFactory.Options();
 opt.inJustDecodeBounds = true;
 Bitmap bmp = BitmapFactory.decodeFile(file, opt);

 // Decode small enough image
 int heightRatio = (int)opt.outHeight/h;
 int widthRatio = (int)opt.outWidth/w;
 if (heightRatio > 1 || widthRatio > 1)
 {
      if (heightRatio > widthRatio)
           opt.inSampleSize = heightRatio;
      else
           opt.inSampleSize = widthRatio; 
 }

 opt.inJustDecodeBounds = false;
 bmp = BitmapFactory.decodeFile(file, opt);

Answer 2

使用ThumbnailUtils课程获取图片/视频的大拇指。

Answer 3

以下方法可用于获取图像缩略图：

private Bitmap getBitmap(String path) {

    Uri uri = getImageUri(path);
    InputStream in = null;
    try {
        final int IMAGE_MAX_SIZE = 1200000; // 1.2MP
        in = mContentResolver.openInputStream(uri);

        // Decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(in, null, o);
        in.close();



        int scale = 1;
        while ((o.outWidth * o.outHeight) * (1 / Math.pow(scale, 2)) > IMAGE_MAX_SIZE) {
            scale++;
        }
        Log.d(TAG, "scale = " + scale + ", orig-width: " + o.outWidth       + ", orig-height: " + o.outHeight);

        Bitmap b = null;
        in = mContentResolver.openInputStream(uri);
        if (scale > 1) {
            scale--;
            // scale to max possible inSampleSize that still yields an image
            // larger than target
            o = new BitmapFactory.Options();
            o.inSampleSize = scale;
            b = BitmapFactory.decodeStream(in, null, o);

            // resize to desired dimensions
            int height = b.getHeight();
            int width = b.getWidth();
            Log.d(TAG, "1th scale operation dimenions - width: " + width    + ", height: " + height);

            double y = Math.sqrt(IMAGE_MAX_SIZE
                    / (((double) width) / height));
            double x = (y / height) * width;

            Bitmap scaledBitmap = Bitmap.createScaledBitmap(b, (int) x,     (int) y, true);
            b.recycle();
            b = scaledBitmap;

            System.gc();
        } else {
            b = BitmapFactory.decodeStream(in);
        }
        in.close();

        Log.d(TAG, "bitmap size - width: " +b.getWidth() + ", height: " + b.getHeight());
        return b;
    } catch (IOException e) {
        Log.e(TAG, e.getMessage(),e);
        return null;
    }
}

使用位图后总是调用bitmap.recycle（）方法。它将从内存中清除位图。还要避免代码中的内存泄漏。这将解决你的OOME。

Answer 4

尝试使用此代码，它可以修复内存不足错误。改变你的身高和宽度。这里的intent_data2是文件路径。

public Bitmap custom_SizedImage(String intent_data2) {
        int targetHeight = 534, targetWidth = 534;
        Options options = new Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(intent_data2, options);
        double sampleSize = 0;
        Boolean scaleByHeight = Math.abs(options.outHeight - targetHeight) >= Math
                .abs(options.outWidth - targetWidth);

        if (options.outHeight * options.outWidth * 2 >= 1638) {
            sampleSize = scaleByHeight ? options.outHeight / targetHeight
                    : options.outWidth / targetWidth;
            sampleSize = (int) Math.pow(2d,
                    Math.floor(Math.log(sampleSize) / Math.log(2d)));
        }
        options.inJustDecodeBounds = false;
        options.inTempStorage = new byte[128];
        while (true) {
            try {
                options.inSampleSize = (int) sampleSize;
                mBitmap = BitmapFactory.decodeFile(intent_data2, options);
                Display display = getWindowManager().getDefaultDisplay();
                int width = display.getWidth();
                int height = display.getHeight();
                int screenDiff = height - width;
                int screenRatio = screenDiff / 3;
                float scaleFactor = mBitmap.getWidth() / width;
                float y_Pos = scaleFactor * screenRatio;
                Matrix matrix = new Matrix();
                matrix.postScale(0.5f, 0.5f);
                croppedBitmap = Bitmap.createBitmap(mBitmap, 0, (int) y_Pos,
                        mBitmap.getWidth(), mBitmap.getWidth(), matrix, true);

                scaledBitmap = Bitmap.createBitmap(targetWidth, targetHeight,
                        Config.RGB_565);

                float ratioX = targetWidth / (float) croppedBitmap.getWidth();
                float ratioY = targetHeight / (float) croppedBitmap.getHeight();
                float middleX = targetWidth / 2.0f;
                float middleY = targetHeight / 2.0f;

                Matrix scaleMatrix = new Matrix();
                scaleMatrix.setScale(ratioX, ratioY, middleX, middleY);

                Canvas canvas = new Canvas(scaledBitmap);
                canvas.setMatrix(scaleMatrix);
                canvas.drawBitmap(croppedBitmap,
                        middleX - croppedBitmap.getWidth() / 2, middleY
                                - croppedBitmap.getHeight() / 2, new Paint(
                                Paint.FILTER_BITMAP_FLAG));
                //saveImage(scaledBitmap);

                break;
            } catch (Exception ex) {
                try {
                    sampleSize = sampleSize * 2;
                } catch (Exception ex1) {

                }
            }
        }
        return scaledBitmap;

}

使用URI从sdcard获取缩略图

4 个答案: