C#•8mo ago

✅ SkiaSharp canvas scale not scaling

I have a method that takes an int[,] array with ones and zeroes. Based on that, I want to create an image, that is optionally resized and blurred. Creating the image at 1:1 scale works, blurring it works as well, but for the love of me I cannot get it to scale...

byte[] CreateImage(int[,] arr, float? scale = null, float? blur = null)
{
    var wSize = arr.GetLength(0);
    var hSize = arr.GetLength(1);
    
    var bmp = new SKBitmap(wSize, hSize);
    using (var canvas = new SKCanvas(bmp))
    {
        for (var w = 0; w < wSize; w++)
        {
            for (var h = 0; h < hSize; h++)
            {
                canvas.DrawPoint(w, h, arr[w, h] == 0 ? SKColors.White : SKColors.Black);
            }
        }

        if (scale is {} s)
        {
            canvas.Scale(s);
        }
    }

    if (blur is {} b)
    {
        var newBmp = new SKBitmap((int)(wSize * scale ?? 1), (int)(hSize * scale ?? 1));
        using var canvas = new SKCanvas(newBmp);
        using var paint = new SKPaint();
        
        paint.ImageFilter = SKImageFilter.CreateBlur(b, b);
        canvas.DrawImage(SKImage.FromBitmap(bmp), 0, 0, paint);
        
        using var blurredImage = SKImage.FromBitmap(newBmp);
        return blurredImage.Encode().ToArray();
    }

    using var image = SKImage.FromBitmap(bmp);
    return image.Encode().ToArray();
}

byte[] CreateImage(int[,] arr, float? scale = null, float? blur = null)
{
    var wSize = arr.GetLength(0);
    var hSize = arr.GetLength(1);
    
    var bmp = new SKBitmap(wSize, hSize);
    using (var canvas = new SKCanvas(bmp))
    {
        for (var w = 0; w < wSize; w++)
        {
            for (var h = 0; h < hSize; h++)
            {
                canvas.DrawPoint(w, h, arr[w, h] == 0 ? SKColors.White : SKColors.Black);
            }
        }

        if (scale is {} s)
        {
            canvas.Scale(s);
        }
    }

    if (blur is {} b)
    {
        var newBmp = new SKBitmap((int)(wSize * scale ?? 1), (int)(hSize * scale ?? 1));
        using var canvas = new SKCanvas(newBmp);
        using var paint = new SKPaint();
        
        paint.ImageFilter = SKImageFilter.CreateBlur(b, b);
        canvas.DrawImage(SKImage.FromBitmap(bmp), 0, 0, paint);
        
        using var blurredImage = SKImage.FromBitmap(newBmp);
        return blurredImage.Encode().ToArray();
    }

    using var image = SKImage.FromBitmap(bmp);
    return image.Encode().ToArray();
}

3 Replies

AngiusOP•8mo ago

ImageSharp looking might compelling right now lol

Kouhai•8mo ago

Canvas.Scale only scales subsequent draw calls, it doesn't scale the canvas itself If you want to scale the bitmap after you've called Canvas.DrawPoint you can do bmp.ScalePixels

AngiusOP•8mo ago

Thanks! I did go with ImageSharp in the end, though, lol

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✅ SkiaSharp canvas scale not scaling