android - 压缩后 Xamarin Forms Android 图像方向发生变化

Question

我正在编写一个 Xamarin 表单 android 应用程序，我正在从图库中获取图像。我想将这些图像上传到服务器，所以我需要它的 byte[] 。我正在缩放和压缩这些图像，然后从中获取 byte[]。我的问题是当我压缩图像时，图像的方向从纵向变为横向。我试过使用“ExifInterface”类并更改图像方向，但它不起作用。以下是我的完整代码:-

protected override async void OnActivityResult (int requestCode, Result resultCode, Intent data)
    {
        if (resultCode == Result.Canceled)
            return;

        try {
            var mediafile = await data.GetMediaFileExtraAsync (Forms.Context);

            byte[] data1 = ReadFully (mediafile.GetStream ());

            byte[] resizedImage = ResizeImageAndroid (data1, 60, 60, mediafile);
            var imageStream = new ByteArrayContent (resizedImage);
            imageStream.Headers.ContentDisposition = new ContentDispositionHeaderValue ("attachment") {
                FileName = Guid.NewGuid () + ".Png"
            };

            var multi = new MultipartContent ();
            multi.Add (imageStream);
            HealthcareProfessionalDataClass lDataClass = HealthcareProfessionalDataClass.Instance;
            lDataClass.Thumbnail = multi;
            App.mByteArrayOfImage = data1;

            System.Diagnostics.Debug.WriteLine (mediafile.Path);

            MessagingCenter.Send<IPictureTaker,string> (this, "picturetaken", mediafile.Path);
        } catch (Java.Lang.Exception e) {
            e.PrintStackTrace ();
        }
    }

public static byte[] ReadFully (System.IO.Stream input)
    {
        using (var ms = new MemoryStream ()) {
            input.CopyTo (ms);
            return ms.ToArray ();
        }
    }

public static byte[] ResizeImageAndroid (byte[] imageData, float width, float height, MediaFile file)
    {
        try {
            // Load the bitmap

            var options = new BitmapFactory.Options ();
            options.InJustDecodeBounds = true;

            // Calculate inSampleSize
            options.InSampleSize = calculateInSampleSize (options, (int)width, (int)height);
            // Decode bitmap with inSampleSize set
            options.InJustDecodeBounds = false;

            Bitmap originalImage = BitmapFactory.DecodeByteArray (imageData, 0, imageData.Length, options);
            Bitmap resizedImage = Bitmap.CreateScaledBitmap (originalImage, (int)width, (int)height, false);


            using (var ms = new MemoryStream ()) {

                resizedImage.Compress (Bitmap.CompressFormat.Png, 0, ms);
                resizedImage = changeOrientation (file, resizedImage);

                return ms.ToArray ();
            }
        } catch (Java.Lang.Exception e) {
            e.PrintStackTrace ();
            return null;
        }
    }

public static int calculateInSampleSize (BitmapFactory.Options options, int reqWidth, int reqHeight)
    {
        // Raw height and width of image
        int height = options.OutHeight;
        int width = options.OutWidth;
        int inSampleSize = 4;

        if (height > reqHeight || width > reqWidth) {

            int halfHeight = height / 2;
            int halfWidth = width / 2;

            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) > reqHeight
                   && (halfWidth / inSampleSize) > reqWidth) {
                inSampleSize *= 2;
            }
        }

        return inSampleSize;
    }

static Bitmap changeOrientation (MediaFile mediafile, Bitmap bitmap)
    {
        var exifInterface = new ExifInterface (mediafile.Path);
        int orientation = exifInterface.GetAttributeInt (ExifInterface.TagOrientation, 0);
        var matrix = new Matrix ();
        switch (orientation) {
        case 2:
            matrix.SetScale (-1, 1);
            break;
        case 3:
            matrix.SetRotate (180);
            break;
        case 4:
            matrix.SetRotate (180);
            matrix.PostScale (-1, 1);
            break;
        case 5:
            matrix.SetRotate (90);
            matrix.PostScale (-1, 1);
            break;
        case 6:
            matrix.SetRotate (90);
            break;
        case 7:
            matrix.SetRotate (-90);
            matrix.PostScale (-1, 1);
            break;
        case 8:
            matrix.SetRotate (-90);
            break;
        default:
            return bitmap;
        }

        try {
            Bitmap oriented = Bitmap.CreateBitmap (bitmap, 0, 0, bitmap.Width, bitmap.Height, matrix, true);
            bitmap.Recycle ();
            return oriented;
        } catch (OutOfMemoryError e) {
            e.PrintStackTrace ();
            return bitmap;
        } catch (System.Exception e) {
            System.Diagnostics.Debug.WriteLine (e.Message);
            return bitmap;
        }
    }

如果有人能解决我的问题，请告诉我。

Answer 1

我不确定我是否错过了它，但感觉矩阵没有分配给任何图像？因此，您对矩阵所做的任何更改都将永远看不到。

我的实现方式是:

    Matrix mtx = new Matrix();
    ExifInterface exif = new ExifInterface(fileName);
    string orientation = exif.GetAttribute(ExifInterface.TagOrientation);

    switch (orientation)
    {
        case "6": // portrait
            mtx.PreRotate(90);
            resizedBitmap = Bitmap.CreateBitmap(resizedBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height, mtx, false);
            mtx.Dispose();
            mtx = null;
            break;
        case "1": // landscape
            break;
        case "8": // Selfie ORIENTATION_ROTATE_270 - might need to flip horizontally too...
            mtx.PreRotate(270);
            resizedBitmap = Bitmap.CreateBitmap(resizedBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height, mtx, false);
            mtx.Dispose();
            mtx = null;
            break;
    }

这是矩阵 .preRotate 分配给 Bitmap.CreateBitmap()，然后返回这个调整大小的位图。我希望这会有所帮助:)