Question

我正在尝试对图像应用过滤器。

XAML：

<Image Name="imageForEditing" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="3" 
       Width="400"  Height="400" Stretch="UniformToFill" />

这是我用来从图片库中获取图片的方法：

public async void pickPhoto()
    {
        FileOpenPicker openPicker = new FileOpenPicker();
        openPicker.ViewMode = PickerViewMode.Thumbnail;
        openPicker.SuggestedStartLocation = PickerLocationId.Desktop;
        openPicker.FileTypeFilter.Add(".jpg");
        openPicker.FileTypeFilter.Add(".png");
        openPicker.FileTypeFilter.Add(".bmp");

        StorageFile file = await openPicker.PickSingleFileAsync();
        if (file != null)
        {
            try
            {
                var stream = await file.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);

                imageForEditing.Source = image;

                wbImage = new WriteableBitmap((int)imageForEditing.ActualWidth,(int) imageForEditing.ActualHeight);
                wbImage.SetSource(stream);
            }
            catch (Exception e)
            {
                MessageDialog msg = new MessageDialog("Greska : " + e.Message);
                msg.ShowAsync();
            }
        }
        else
        {
            (Application.Current as App).isEditorNext = false;
            this.Frame.Navigate(typeof(SplashScreen));
        }
    }

wbImage是一个全局变量

所以，当我尝试在图像上应用效果时，我得到一个异常，说我的值不应该为空。

以下是灰度效果的代码（我甚至不知道它是否有效，我还没有尝试过它）

private WriteableBitmap GrayScale(WriteableBitmap modifiedImage)
    {
        try
        {
            int r = 0, a = 0, i = 0;
            int h = modifiedImage.PixelHeight;
            int w = modifiedImage.PixelWidth;

            using (Stream stream = modifiedImage.PixelBuffer.AsStream())
            {
                byte[] StreamBuffer = new byte[modifiedImage.PixelBuffer.Length];
                byte[] tempbuffer = new byte[64000];
                stream.Seek(0, 0);
                stream.Read(StreamBuffer, 0, StreamBuffer.Length);

                for (i = 0; i < StreamBuffer.Length - 4; i = i + 4)
                {
                    var a1 = StreamBuffer[i + 3];
                    var r1 = StreamBuffer[i + 2];
                    var g1 = StreamBuffer[i + 1];
                    var b1 = StreamBuffer[i + 0];

                    a = 0xff;
                    r = (byte)((0.311 * r1) + (0.486 * g1) + (0.213 * b1));
                    StreamBuffer[i + 3] = (byte)a;
                    StreamBuffer[i + 2] = (byte)(r > 255 ? 255 : (r < 0 ? 0 : r));
                    StreamBuffer[i + 1] = (byte)(r > 255 ? 255 : (r < 0 ? 0 : r));
                    StreamBuffer[i + 0] = (byte)(r > 255 ? 255 : (r < 0 ? 0 : r));
                }
                stream.Seek(0, 0);
                stream.Write(StreamBuffer, 0, StreamBuffer.Length);
                modifiedImage.Invalidate();
            }
        }
        catch (Exception ex)
        {
             var exceptionMessageDialog = new Windows.UI.Popups.MessageDialog("Exception : " + ex.Message);
            exceptionMessageDialog.ShowAsync();
        }

此处抛出异常：

Stream stream = modifiedImage.PixelBuffer.AsStream();

我做错了什么？我已经搜索了超过5个小时的答案。似乎没有任何帮助。

我检查modifiedImage是否为空，但似乎没问题。以下是调用方法的方法以及我设置imageForEditing.Source的位置。

        wbImage = GrayScale(wbImage);
        imageForEditing.Source = wbImage;

对图像应用灰度效果

0 个答案: