java - 从 Uri 创建调整大小的位图的正确方法是什么？

Question

我正在尝试从 Uri 创建一个调整大小的位图。
在网上搜索时，我看到了几个部分示例，只是感到困惑。
创建此任务的正确方法是什么？

谢谢。

Answer 1

您应该阅读一篇非常好的资源文章：

http://developer.android.com/training/displaying-bitmaps/index.html

这里有一些代码，取自这篇文章：

public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight) {
   // First decode with inJustDecodeBounds=true to check dimensions
   final BitmapFactory.Options options = new BitmapFactory.Options();
   options.inJustDecodeBounds = true;
   BitmapFactory.decodeResource(res, resId, options);
   // Calculate inSampleSize
   options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
   // Decode bitmap with inSampleSize set
   options.inJustDecodeBounds = false;
   return BitmapFactory.decodeResource(res, resId, options);
}

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    // Raw height and width of image
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;

    if (height > reqHeight || width > reqWidth) {
        if (width > height) {
            inSampleSize = Math.round((float) height / (float) reqHeight);
        } else {
            inSampleSize = Math.round((float) width / (float) reqWidth);
        }

        // This offers some additional logic in case the image has a strange
        // aspect ratio. For example, a panorama may have a much larger
        // width than height. In these cases the total pixels might still
        // end up being too large to fit comfortably in memory, so we should
        // be more aggressive with sample down the image (=larger
        // inSampleSize).

        final float totalPixels = width * height;

        // Anything more than 2x the requested pixels we'll sample down
        // further.
        final float totalReqPixelsCap = reqWidth * reqHeight * 2;

        while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
            inSampleSize++;
        }
    }
    return inSampleSize;
}

Answer 2

矩阵矩阵 = 新矩阵（）；matrix.postScale(xScale, yScale); 位图 newBitmap = Bitmap.createBitmap(oldBitmap, 0, 0, orgWidth, orgHeight, matrix, true);

如果要减小大小，则 xScale 和 yScale 应为负数，否则为正数:)