在WPF中调整图像大小

Question

我有一个图像,我想重新调整大小,需要保存在我的临时文件夹中.

我试过的如下:

UIElement uie = CanvasHost.Child;
int width = 800;
int height = (int)((width / (double)((FrameworkElement)uie).Width) * (int)((FrameworkElement)uie).Height);          
RenderTargetBitmap rtb = new RenderTargetBitmap(width, height, 96, 96, PixelFormats.Pbgra32);
rtb.Render(uie);

string dir = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData) + @"\temp\";
if (!Directory.Exists(dir))
      Directory.CreateDirectory(dir);

long size = 0;

string filePath = dir + DateTime.Now.Ticks.ToString() + (isPng ? ".png" : ".jpg");
BitmapEncoder enc = null;

using (FileStream fs = File.Create(filePath))
{
    if (isPng)
        enc = new PngBitmapEncoder();
    else
        enc = new JpegBitmapEncoder();

    enc.Frames.Add(BitmapFrame.Create(rtb));
    enc.Save(fs);

    size = fs.Length;
}

但是当我像这样创建图像时,它会将部分图像保存在临时文件夹中.(如上图所示)

我该如何调整全尺寸？我错过了什么？

编辑: 正如Erti-Chris Eelmaa提到的上述答案所述,我已经更改了以下代码.它有效......

UIElement uie = CanvasHost.Child;
int width = DataCache.Instance.CurrentProject.MaxPhotoEdgeSize;
int height = (int)((width / (double)((FrameworkElement)uie).Width) * (int)((FrameworkElement)uie).Height);

RenderTargetBitmap rtb = new RenderTargetBitmap((int)((FrameworkElement)uie).Width, (int)((FrameworkElement)uie).Height, 96, 96, PixelFormats.Pbgra32);
rtb.Render(uie);

ImageSource im = (ImageSource)rtb.Clone();
BitmapFrame bp = CreateResizedImage(im, width, height, 1); //method suggested by Erti-Chris Eelmaa
string dir = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData) + @"\temp\";

if (!Directory.Exists(dir))
    Directory.CreateDirectory(dir);

long size = 0;

string filePath = dir + DateTime.Now.Ticks.ToString() + (isPng ? ".png" : ".jpg");
BitmapEncoder enc = null;

using (FileStream fs = File.Create(filePath))
{
    if (isPng)
         enc = new PngBitmapEncoder();
    else
         enc = new JpegBitmapEncoder();


    enc.Frames.Add(BitmapFrame.Create(bp));
    enc.Save(fs);

    size = fs.Length;
}

Answer 1

至于调整大小本身,使用WPF TransformedBitmap似乎更容易:

var bitmap = new TransformedBitmap(bitmapSource, 
    new ScaleTransform(
        newWidth / bitmapSource.PixelWidth, 
        newHeight / bitmapSource.PixelHeight));

Answer 2

只需使用此方法获取BitmapFrame,之后您可以使用PngBitmapEncoder将其保存到HDD.

private static BitmapFrame CreateResizedImage(ImageSource source, int width, int height, int margin)
{
    var rect = new Rect(margin, margin, width - margin * 2, height - margin * 2);

    var group = new DrawingGroup();
    RenderOptions.SetBitmapScalingMode(group, BitmapScalingMode.HighQuality);
    group.Children.Add(new ImageDrawing(source, rect));

    var drawingVisual = new DrawingVisual();
    using (var drawingContext = drawingVisual.RenderOpen())
        drawingContext.DrawDrawing(group);

    var resizedImage = new RenderTargetBitmap(
        width, height,         // Resized dimensions
        96, 96,                // Default DPI values
        PixelFormats.Default); // Default pixel format
    resizedImage.Render(drawingVisual);

    return BitmapFrame.Create(resizedImage);
}