TransformedBitmap Scaling Mode

Question

I'm using a TransformedBitmap class to draw scaled images to a Bitmap using TransformedBitmap.CopyPixels. Is there a way to specify the scaling mode that is used? RenderOptions.SetBitmapScalingMode doesn't seem to affect anything. I would like to use nearest neighbor but it appears to use a bi linear filter of some sort.

score 3 · Accepted Answer · edited May 23 '17 at 10:27

3

It is not possible to specify the scaling algorithm, it is by design.
The RenderOptions.SetBitmapScalingMode applies to rendering only, e.g. you have a 32*32 icon and want to show it at 256*256 but still in a blocky way (nearest neighbour)

Update

A few ways on how you could overcome this issue :

Do it by yourself : http://tech-algorithm.com/articles/nearest-neighbor-image-scaling/

Using Forms : https://stackoverflow.com/a/1856362/361899

Custom drawing : How to specify the image scaling algorithm used by a WPF Image?

There is AForge too but that might be overkill for your needs.

Update 2

WriteableBitmapEx will probably do the job easily for you : http://writeablebitmapex.codeplex.com/

You can resize a WriteableBitmap, specify interpolation mode and there is nearest neighbor.

Both TransformedBitmap and WriteableBitmapEx inherit from BitmapSource, likely you'll have no change to make at all to your existing code.

edited May 23 '17 at 10:27

Community

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answered Apr 05 '13 at 01:32

aybe

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Interesting, do you have any suggestions for an alternative? (Given that I have a bitmapsource which needs to be scaled and copied to a Bitmap) – phosphoer Apr 05 '13 at 18:40
I've added a few ways for you in my answer. (sorry but I'm on my phone and it's not very practical) – aybe Apr 05 '13 at 23:42
1

The WriteableBitmapEx looks like the thing to use, thank you! – phosphoer Apr 09 '13 at 18:38

score 1 · Answer 2 · answered Aug 29 '14 at 14:18

 public static class Extensions
{
    public static BitmapFrame Resize(this
BitmapSource photo, int width, int height,
BitmapScalingMode scalingMode)
    {

        var group = new DrawingGroup();
        RenderOptions.SetBitmapScalingMode(
            group, scalingMode);
        group.Children.Add(
            new ImageDrawing(photo,
                new Rect(0, 0, width, height)));
        var targetVisual = new DrawingVisual();
        var targetContext = targetVisual.RenderOpen();
        targetContext.DrawDrawing(group);
        var target = new RenderTargetBitmap(
            width, height, 96, 96, PixelFormats.Default);
        targetContext.Close();
        target.Render(targetVisual);
        var targetFrame = BitmapFrame.Create(target);
        return targetFrame;
    }
}

Took from http://weblogs.asp.net/bleroy/resizing-images-from-the-server-using-wpf-wic-instead-of-gdi

TransformedBitmap Scaling Mode

2 Answers2