如何从另一个 SoftwareBitmap (UWP) 的区域创建 SoftwareBitmap [英] How to create a SoftwareBitmap from region of another SoftwareBitmap (UWP)

问题描述

创建具有另一个区域副本(例如BitmapBounds)的新Windows.Graphics.Imaging.SoftwareBitmap 对象的最有效(最简单)方法是什么?SoftwareBitmap 对象(深拷贝)，用于 Windows UWP 应用程序?

What is the most efficient (easiest) way to create a new Windows.Graphics.Imaging.SoftwareBitmap object with a copy of region (BitmapBounds for example) of another SoftwareBitmap object (deep copy), for Windows UWP application?

SoftwareBitmap 没有这样的构造函数或静态方法.所有 Copy* 方法都复制整个位图.

There is no such constructor or static method for SoftwareBitmap. All Copy* methods copies whole bitmap.

我使用 WriteableBitmap 来实现这一点:

I played with WriteableBitmap to achieve this:

    SoftwareBitmap CreateFromBitmap(SoftwareBitmap bmp, Rect rect)
    {
        WriteableBitmap wbmpIn = new WriteableBitmap(bmp.PixelWidth, bmp.PixelHeight);
        bmp.CopyToBuffer(wbmpIn.PixelBuffer);

        WriteableBitmap wbmpOut = new WriteableBitmap((int)rect.Width, (int)rect.Height);
        wbmpOut.Blit(new Rect(0, 0, rect.Width, rect.Height), wbmpIn, rect);

        SoftwareBitmap ret = new SoftwareBitmap(bmp.BitmapPixelFormat, (int)rect.Width, (int)rect.Height);
        ret.CopyFromBuffer(wbmpOut.PixelBuffer);

        return ret;
    }

但它看起来并不有效 - 涉及两个 CopyFromBuffer() 和一个 Blit().

But it doesn't look effective - involves two CopyFromBuffer() and one Blit().

有没有更有效的解决方案?

Is there a more efficient solution?

推荐答案

您可以参考以下代码，它可以从现有的 SoftwareBitmap 创建一个新的裁剪 SoftwareBitmap.

You can refer to following code, it can create a new cropped SoftwareBitmap from an existing SoftwareBitmap.

    private async Task<SoftwareBitmap> CreateFromBitmap(SoftwareBitmap softwareBitmap, Rect rect)
    {
        using (InMemoryRandomAccessStream stream = new InMemoryRandomAccessStream())
        {
            BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.BmpEncoderId, stream);

            encoder.SetSoftwareBitmap(softwareBitmap);

            encoder.BitmapTransform.Bounds = new BitmapBounds()
            {
                X = (uint)rect.X,
                Y = (uint)rect.Y,
                Height = (uint)rect.Height,
                Width = (uint)rect.Width
            };

            await encoder.FlushAsync();

            BitmapDecoder decoder = await BitmapDecoder.CreateAsync(stream);

            return await decoder.GetSoftwareBitmapAsync(softwareBitmap.BitmapPixelFormat, softwareBitmap.BitmapAlphaMode);
        }
    }



    var croppedBitmap = await CreateFromBitmap(sourceSoftwareBmp, new Rect(0, 0, 200, 100));

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