Question

我正在寻找从Windows应用商店应用程序保存画布的方法，我发现：

private void CreateSaveBitmap(Canvas canvas, string filename)
     {
       RenderTargetBitmap renderBitmap = new RenderTargetBitmap(
        (int)canvas.Width, (int)canvas.Height,
        96d, 96d, PixelFormats.Pbgra32);
      // needed otherwise the image output is black
       canvas.Measure(new Size((int)canvas.Width, (int)canvas.Height));
       canvas.Arrange(new Rect(new Size((int)canvas.Width, (int)canvas.Height)));

renderBitmap.Render(canvas);

//JpegBitmapEncoder encoder = new JpegBitmapEncoder();
       PngBitmapEncoder encoder = new PngBitmapEncoder();
       encoder.Frames.Add(BitmapFrame.Create(renderBitmap));

using (FileStream file = File.Create(filename))
       {
         encoder.Save(file);
       }
     }

但是该方法在windows store app中不起作用（RenderTargetBitmap没有PngBitmapEncoder没有5个参数构造函数。所以我的问题是如何从windows商店应用程序中保存画布，因为某种图像文件（jpg，png等）有什么方法可以做到这一点？

Answer 1

试试这个

using System.Runtime.InteropServices.WindowsRuntime

private async Task CreateSaveBitmapAsync(Canvas canvas)
{
    if (canvas != null)
    {
        RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
        await renderTargetBitmap.RenderAsync(canvas);

        var picker = new FileSavePicker();
        picker.FileTypeChoices.Add("JPEG Image", new string[] { ".jpg" });
        StorageFile file = await picker.PickSaveFileAsync();
        if (file != null)
        {
            var pixels = await renderTargetBitmap.GetPixelsAsync();

            using (IRandomAccessStream stream = await file.OpenAsync(FileAccessMode.ReadWrite))
            {
                var encoder = await
                    BitmapEncoder.CreateAsync(BitmapEncoder.JpegEncoderId, stream);
                byte[] bytes = pixels.ToArray();
                encoder.SetPixelData(BitmapPixelFormat.Bgra8,
                                     BitmapAlphaMode.Ignore,
                                     (uint)canvas.Width, (uint)canvas.Height,
                                     96, 96, bytes);

                await encoder.FlushAsync();
            }
        } 
    }
}

Answer 2

我遇到了这个回复，虽然它看起来正是我要找的东西但是没有用。添加错误处理程序显示：

价值不在预期范围内。

最后我发现：

(uint)canvas.Width, (uint)canvas.Height,

均为0.将其替换为：

(uint)canvas.ActualWidth, (uint)canvas.ActualHeight,

它奏效了。不知道为什么它适用于Carlos28而不适合我，但是这个改变对我也有用，所以我感谢Xyriod的回答

Answer 3

Xyroid，谢谢您的想法和结构。为了使CreateSaveBitmapAsync（）的版本在04/24/20上运行，我必须用以下内容替换您的using块。硬编码“ 96”的更改以及用其定义替换“字节”是可选的。

using (Windows.Storage.Streams.IRandomAccessStream stream = await fileToWhichToSave.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
{
    Windows.Graphics.Imaging.BitmapEncoder encoder = await Windows.Graphics.Imaging.BitmapEncoder.CreateAsync(Windows.Graphics.Imaging.BitmapEncoder.JpegEncoderId, stream);
    encoder.SetPixelData(
        Windows.Graphics.Imaging.BitmapPixelFormat.Bgra8,
        Windows.Graphics.Imaging.BitmapAlphaMode.Ignore,
        (uint)renderTargetBitmap.PixelWidth,
        (uint)renderTargetBitmap.PixelHeight,
        Windows.Graphics.Display.DisplayInformation.GetForCurrentView().LogicalDpi,
        Windows.Graphics.Display.DisplayInformation.GetForCurrentView().LogicalDpi,
        pixels.ToArray());
    await encoder.FlushAsync();
}

将画布从Windows应用商店保存为图像文件

3 个答案: