c# - 从库中选择图像并压缩 windows phone 8.1

Question

在这段代码中，我首先从 Windows Phone 照片库中选取图像，然后将其压缩以便上传。但是我在压缩时遇到了一些问题，因为当我在 BitmapEncoder 中使用 FlushAsync 时，原始的 final 没有被覆盖并且发生异常。这是我的代码

从库中选择图片

ImagePath = string.Empty;
                    FileOpenPicker filePicker = new FileOpenPicker();
                    filePicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
                    filePicker.ViewMode = PickerViewMode.Thumbnail;

                    // Filter to include a sample subset of file types
                    filePicker.FileTypeFilter.Clear();
                    filePicker.FileTypeFilter.Add(".bmp");
                    filePicker.FileTypeFilter.Add(".png");
                    filePicker.FileTypeFilter.Add(".jpeg");
                    filePicker.FileTypeFilter.Add(".jpg");
                    filePicker.PickMultipleFilesAndContinue();
                    view.Activated += viewActivated; 

解码和压缩图像

FileOpenPickerContinuationEventArgs args = args1 as FileOpenPickerContinuationEventArgs;
        if (args != null)
        {
            try
            {
            if (args.Files.Count == 0) return;
            view.Activated -= viewActivated;
            userLoginResponse = await DataManager.GetLoginResponseAsync();
            for (int no = 0; (no < args.Files.Count && no < 4); no++)
            {
                StorageFile storageFile = args.Files[no];
                var stream = await storageFile.OpenAsync(FileAccessMode.ReadWrite);

                var bitmapImage = new Windows.UI.Xaml.Media.Imaging.BitmapImage();
                await bitmapImage.SetSourceAsync(stream);
                var decoder = await BitmapDecoder.CreateAsync(stream);
                PixelDataProvider pixelData = await decoder.GetPixelDataAsync();
                var data = pixelData.DetachPixelData();

                BitmapPropertySet propertySet = new BitmapPropertySet();
                BitmapTypedValue qualityValue = new BitmapTypedValue(1.0, Windows.Foundation.PropertyType.Single);
                propertySet.Add("ImageQuality", qualityValue);
                BitmapEncoder be = await BitmapEncoder.CreateAsync(BitmapEncoder.BmpEncoderId, stream);
                be.SetPixelData(BitmapPixelFormat.Rgba8, BitmapAlphaMode.Straight, 480, 480, 50, 50, data);
                await be.FlushAsync();

任何人都可以提出解决此问题的方法。提前致谢

Answer 1

我使用诺基亚成像 SDK 来完成此任务。只需将 SDK 添加到您的解决方案中 using NuGet.然后包括

using Lumia.Imaging;

在您的代码文件中。之后，您可以使用以下代码从 StorageFile 读取图像数据并将其压缩为 byte[]，然后您可以将其上传到您的服务器:

byte[] compressedImageBytes = null;
IRandomAccessStream fileStream = await file.OpenAsync(FileAccessMode.Read); // "file" being the StorageFile from your FileOpenPicker
if (file.Name.ToLower().EndsWith(".jpg") || file.Name.ToLower().EndsWith(".jpeg"))
{
    using (StreamImageSource source = new StreamImageSource(fileStream.AsStreamForRead()))
    {
        IFilterEffect effect = new FilterEffect(source);
        using (JpegRenderer renderer = new JpegRenderer(effect))
        {
            renderer.Quality = 0.7; // higher value means better quality
            IBuffer buffer = await renderer.RenderAsync();
            Windows.Security.Cryptography.CryptographicBuffer.CopyToByteArray(buffer, out compressedImageBytes);
        }
    }
}}

if (compressedImageBytes != null)
{
    //you can upload or safe the byte-array of the compressed image
}