在 UWP 中使用 RenderTargetBitmap 时出错 [英] Error using using RenderTargetBitmap in UWP

问题描述

我正在尝试创建位图图像，并具有以下代码:

I'm trying to create a bitmap image, and have the following code:

RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(uielement);

IBuffer pixels = await renderTargetBitmap.GetPixelsAsync();

. . .

var pixelArray = pixels.ToArray();

为了获得 ToArray() 扩展，我遇到了 这个 问题.所以我补充说:

In order to get a ToArray() extension, I came across this question. So I added:

using System.Runtime.InteropServices.WindowsRuntime; // For ToArray

我的代码.但是，当我运行时，出现以下错误:

To my code. However, when I run, I get the following error:

抛出异常:'System.ArgumentException' inSystem.Runtime.WindowsRuntime.dll

Exception thrown: 'System.ArgumentException' in System.Runtime.WindowsRuntime.dll

附加信息:指定的缓冲区索引不在缓冲容量.

Additional information: The specified buffer index is not within the buffer capacity.

当我深入了解细节时，它在堆栈跟踪中说:

When I drill into the details, it says in the Stack Trace:

at >System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions.ToArray(IBuffer source, UInt32 sourceIndex, Int32 count)在 >System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions.ToArray(IBuffer 源)

at >System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions.ToArray(IBuffer source, UInt32 sourceIndex, Int32 count) at >System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions.ToArray(IBuffer source)

这种提取像素阵列的方法是否仍然适用于UWP?如果是，有什么办法可以从这个错误消息中获取更多详细信息?

Is this method of extracting a pixel array still applicable to the UWP? If it is, is there any way to get more detail from this error message?

推荐答案

那个提取像素数组的方法绝对适用于UWP.至于错误，反编译的ToArray()是这样的:

That method of extracting a pixel array is definitely applicable to UWP. As for the error, the decompiled ToArray() goes like this:

public static byte[] ToArray(this IBuffer source)
{
  if (source == null)
    throw new ArgumentNullException("source");
  return WindowsRuntimeBufferExtensions.ToArray(source, 0U, checked ((int) source.Length));
}

换句话说，它调用带有起始索引和长度的 ToArray 重载:

In other words, it calls the ToArray overload that takes a start index and a length:

public static byte[] ToArray(this IBuffer source, uint sourceIndex, int count)
{
  if (source == null)
    throw new ArgumentNullException("source");
  if (count < 0)
    throw new ArgumentOutOfRangeException("count");
  if (sourceIndex < 0U)
    throw new ArgumentOutOfRangeException("sourceIndex");
  if (source.Capacity <= sourceIndex)
    throw new ArgumentException(SR.GetString("Argument_BufferIndexExceedsCapacity"));
  if ((long) (source.Capacity - sourceIndex) < (long) count)
    throw new ArgumentException(SR.GetString("Argument_InsufficientSpaceInSourceBuffer"));
  byte[] destination = new byte[count];
  WindowsRuntimeBufferExtensions.CopyTo(source, sourceIndex, destination, 0, count);
  return destination;
}

几乎肯定会导致您的问题的行:

The line(s) almost certainly causing your problem:

  if (source.Capacity <= sourceIndex)
    throw new ArgumentException(SR.GetString("Argument_BufferIndexExceedsCapacity"));

...并且由于 sourceIndex 必须为 0，这意味着 source.Capacity 也是 0.

...and since sourceIndex is necessarily 0, that would mean that source.Capacity is also 0.

我建议您在代码中添加一些检测以检查 IBuffer:

I suggest you add some instrumentation to your code to inspect the IBuffer:

RenderTargetBitmap rtb = new RenderTargetBitmap();
await rtb.RenderAsync(element);

IBuffer pixelBuffer = await rtb.GetPixelsAsync();
Debug.WriteLine($"Capacity = {pixelBuffer.Capacity}, Length={pixelBuffer.Length}");
byte[] pixels = pixelBuffer.ToArray();

我认为您的问题很可能发生在 ToArray 调用之前.我在自己的 UWP 应用程序中使用完全相同的序列，获得如下调试输出:

I think it likely that your problem occurs before the ToArray call. I'm using the exact same sequence in my own UWP app, getting debug output like so:

Capacity = 216720, Length=216720

这篇关于在 UWP 中使用 RenderTargetBitmap 时出错的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！