Question

我想将图像文件从本地磁盘加载到writeablebitmap图像，因此我可以让用户对其进行编辑。当我创建一个WriteableBitmap对象时，构造函数需要pixelwidth和pixelheight参数，我不知道从哪里得到这两个，任何人都可以帮忙吗？

Answer 1

尝试以下代码。有一种直接的方法（使用 BitmapImage 加载图像，然后将此对象直接传递给 WriteableBitmap 构造函数，但我不确定这是否按预期工作或它有性能问题，不记得了）：

BitmapSource bmp = BitmapFrame.Create(
    new Uri(@"C:\Users\Public\Pictures\Sample Pictures\Koala.jpg", UriKind.Relative),
    BitmapCreateOptions.None, BitmapCacheOption.OnLoad);

if (bmp.Format != PixelFormats.Bgra32)
    bmp = new FormatConvertedBitmap(bmp, PixelFormats.Bgra32, null, 1);
    // Just ignore the last parameter

WriteableBitmap wbmp = new WriteableBitmap(bmp.PixelWidth, bmp.PixelHeight,
    kbmp.DpiX, bmp.DpiY, bmp.Format, bmp.Palette);

Int32Rect r = new Int32Rect(0, 0, bmp.PixelWidth, bmp.PixelHeight);
wbmp.Lock();
bmp.CopyPixels(r, wbmp.BackBuffer, wbmp.BackBufferStride * wbmp.PixelHeight,
    wbmp.BackBufferStride);

wbmp.AddDirtyRect(r);
wbmp.Unlock();

Answer 2

在定义WriteableBitmap图像时不要关心pixelWidth和pixelHeight，请试试这个：

using (IRandomAccessStream stream = await file.OpenAsync(FileAccessMode.ReadWrite))
{
    WriteableBitmap image = new WriteableBitmap(1, 1);
    image.SetSource(stream);
    WriteableBitmapImage.Source = image;
}

Answer 3

如果你想拥有正确的像素宽度和高度，你需要首先将它加载到BitmapImage中以正确填充它：

StorageFile storageFile =
    await StorageFile.GetFileFromApplicationUriAsync("ms-appx:///myimage.png");
using (IRandomAccessStream fileStream = await storageFile.OpenAsync(FileAccessMode.Read))
{
    BitmapImage bitmapImage = new BitmapImage();
    await bitmapImage.SetSourceAsync(fileStream);

    WriteableBitmap writeableBitmap =
        new WriteableBitmap(bitmapImage.PixelWidth, bitmapImage.PixelHeight);
    fileStream.Seek(0);
    await writeableBitmap.SetSourceAsync(fileStream);
}

（适用于WinRT应用）

如何在windows8中从图像文件创建writeablebitmap图像

3 个答案: